Science.gov

Sample records for formation rates revealed

  1. Southern Ocean frontal structure and sea-ice formation rates revealed by elephant seals

    PubMed Central

    Charrassin, J.-B.; Hindell, M.; Rintoul, S. R.; Roquet, F.; Sokolov, S.; Biuw, M.; Costa, D.; Boehme, L.; Lovell, P.; Coleman, R.; Timmermann, R.; Meijers, A.; Meredith, M.; Park, Y.-H.; Bailleul, F.; Goebel, M.; Tremblay, Y.; Bost, C.-A.; McMahon, C. R.; Field, I. C.; Fedak, M. A.; Guinet, C.

    2008-01-01

    Polar regions are particularly sensitive to climate change, with the potential for significant feedbacks between ocean circulation, sea ice, and the ocean carbon cycle. However, the difficulty in obtaining in situ data means that our ability to detect and interpret change is very limited, especially in the Southern Ocean, where the ocean beneath the sea ice remains almost entirely unobserved and the rate of sea-ice formation is poorly known. Here, we show that southern elephant seals (Mirounga leonina) equipped with oceanographic sensors can measure ocean structure and water mass changes in regions and seasons rarely observed with traditional oceanographic platforms. In particular, seals provided a 30-fold increase in hydrographic profiles from the sea-ice zone, allowing the major fronts to be mapped south of 60°S and sea-ice formation rates to be inferred from changes in upper ocean salinity. Sea-ice production rates peaked in early winter (April–May) during the rapid northward expansion of the pack ice and declined by a factor of 2 to 3 between May and August, in agreement with a three-dimensional coupled ocean–sea-ice model. By measuring the high-latitude ocean during winter, elephant seals fill a “blind spot” in our sampling coverage, enabling the establishment of a truly global ocean-observing system. PMID:18695241

  2. Southern Ocean frontal structure and sea-ice formation rates revealed by elephant seals.

    PubMed

    Charrassin, J-B; Hindell, M; Rintoul, S R; Roquet, F; Sokolov, S; Biuw, M; Costa, D; Boehme, L; Lovell, P; Coleman, R; Timmermann, R; Meijers, A; Meredith, M; Park, Y-H; Bailleul, F; Goebel, M; Tremblay, Y; Bost, C-A; McMahon, C R; Field, I C; Fedak, M A; Guinet, C

    2008-08-19

    Polar regions are particularly sensitive to climate change, with the potential for significant feedbacks between ocean circulation, sea ice, and the ocean carbon cycle. However, the difficulty in obtaining in situ data means that our ability to detect and interpret change is very limited, especially in the Southern Ocean, where the ocean beneath the sea ice remains almost entirely unobserved and the rate of sea-ice formation is poorly known. Here, we show that southern elephant seals (Mirounga leonina) equipped with oceanographic sensors can measure ocean structure and water mass changes in regions and seasons rarely observed with traditional oceanographic platforms. In particular, seals provided a 30-fold increase in hydrographic profiles from the sea-ice zone, allowing the major fronts to be mapped south of 60 degrees S and sea-ice formation rates to be inferred from changes in upper ocean salinity. Sea-ice production rates peaked in early winter (April-May) during the rapid northward expansion of the pack ice and declined by a factor of 2 to 3 between May and August, in agreement with a three-dimensional coupled ocean-sea-ice model. By measuring the high-latitude ocean during winter, elephant seals fill a "blind spot" in our sampling coverage, enabling the establishment of a truly global ocean-observing system. PMID:18695241

  3. Rates of formation and dissipation of clumping reveal lagged responses in tropical tree populations.

    PubMed

    Detto, Matteo; Muller-Landau, Helene C

    2016-05-01

    The dynamics of spatial patterns of plant populations can provide important information about underlying processes, yet they have received relatively little attention to date. Here we investigate the rates of formation and dissipation of clusters and the relationship of these rates to the degree of aggregation (clumping) in models and in empirical data for tropical trees. In univariate models, exact solutions and simulations show that the rate of change of spatial patterns has a specific, linear relationship to the degree of aggregation at all scales. Shorter dispersal and/or weaker negative density dependence (NDD) result in both denser and longer-lasting clusters. In multivariate host-parasite models in contrast, the rate of change of spatial pattern is faster relative to the level of aggrega- tion. We then analyzed the dynamics of spatial patterns of stems ≥ 1 cm diameter in 221 tropical tree species from seven censuses spanning 28 yr. We found that for most species, the rates of change in spatial patterns were faster than predicted from univariate models given their aggregation. This indicates that more complex dynamics involving multivariate interactions induce time lags in responses to aggregation in these species. Such lags could arise, for example, if it takes time for natural enemies to locate aggregations of their hosts. This combination of theoretical and empirical results thus shows that complex multilevel models are needed to capture spatiotemporal dynamics of tropical forests and provides new insights into the processes structuring tropical plant communities. PMID:27349094

  4. Mammalian phylogeny reveals recent diversification rate shifts.

    PubMed

    Stadler, Tanja

    2011-04-12

    Phylogenetic trees of present-day species allow investigation of the rate of evolution that led to the present-day diversity. A recent analysis of the mammalian phylogeny challenged the view of explosive mammalian evolution after the Cretaceous-Tertiary (K/T) boundary (65 Mya). However, due to lack of appropriate methods, the diversification (speciation minus extinction) rates in the more recent past of mammalian evolution could not be determined. In this paper, I provide a method that reveals that the tempo of mammalian evolution did not change until ∼ 33 Mya. This constant period was followed by a peak of diversification rates between 33 and 30 Mya. Thereafter, diversification rates remained high and constant until 8.55 Mya. Diversification rates declined significantly at 8.55 and 3.35 Mya. Investigation of mammalian subgroups (marsupials, placentals, and the six largest placental subgroups) reveals that the diversification rate peak at 33-30 Mya is mainly driven by rodents, cetartiodactyla, and marsupials. The recent diversification rate decrease is significant for all analyzed subgroups but eulipotyphla, cetartiodactyla, and primates. My likelihood approach is not limited to mammalian evolution. It provides a robust framework to infer diversification rate changes and mass extinction events in phylogenies, reconstructed from, e.g., present-day species or virus data. In particular, the method is very robust toward noise and uncertainty in the phylogeny and can account for incomplete taxon sampling. PMID:21444816

  5. Revealing Educationally Critical Aspects of Rate

    ERIC Educational Resources Information Center

    Herbert, Sandra; Pierce, Robyn

    2012-01-01

    Rate (of change) is an important but complicated mathematical concept describing a ratio comparing two different numeric, measurable quantities. Research referring to students' difficulties with this concept spans more than 20 years. It suggests that problems experienced by some calculus students are likely a result of pre-existing limited or…

  6. Measuring star formation rates in blue galaxies

    NASA Technical Reports Server (NTRS)

    Gallagher, John S., III; Hunter, Deidre A.

    1987-01-01

    The problems associated with measurements of star formation rates in galaxies are briefly reviewed, and specific models are presented for determinations of current star formation rates from H alpha and Far Infrared (FIR) luminosities. The models are applied to a sample of optically blue irregular galaxies, and the results are discussed in terms of star forming histories. It appears likely that typical irregular galaxies are forming stars at nearly constant rates, although a few examples of systems with enhanced star forming activity are found among HII regions and luminous irregular galaxies.

  7. Magnetic fields and galactic star formation rates

    SciTech Connect

    Loo, Sven Van; Tan, Jonathan C.; Falle, Sam A. E. G.

    2015-02-10

    The regulation of galactic-scale star formation rates (SFRs) is a basic problem for theories of galaxy formation and evolution: which processes are responsible for making observed star formation rates so inefficient compared to maximal rates of gas content divided by dynamical timescale? Here we study the effect of magnetic fields of different strengths on the evolution of giant molecular clouds (GMCs) within a kiloparsec patch of a disk galaxy and resolving scales down to ≃0.5 pc. Including an empirically motivated prescription for star formation from dense gas (n{sub H}>10{sup 5} cm{sup −3}) at an efficiency of 2% per local free-fall time, we derive the amount of suppression of star formation by magnetic fields compared to the nonmagnetized case. We find GMC fragmentation, dense clump formation, and SFR can be significantly affected by the inclusion of magnetic fields, especially in our strongest investigated B-field case of 80 μG. However, our chosen kiloparsec-scale region, extracted from a global galaxy simulation, happens to contain a starbursting cloud complex that is only modestly affected by these magnetic fields and likely requires internal star formation feedback to regulate its SFR.

  8. Star formation rate in the solar neighborhood

    NASA Astrophysics Data System (ADS)

    Cignoni, Michele

    2006-08-01

    This thesis develops a method for obtaining the star formation histories of a mixed, resolved population through the use of color-magnitude diagrams (CMDs). The method is applied to the derivation of the local star formation rate, modeling observations of the Hipparcos satellite wigth synthetic CMDs computed for different star formation histories with an updated stellar evolution library. Parallax and photometric uncertainties are included explicitly and corrected using the Bayesian Richardson-Lucy algorithm. We find that the solar neighborhood star formation rate has a characteristic timescale for variation of about 6 Gyr, with a maximum activity close to 3 Gyr ago. This suggests a global, rather than local, star forming event. The summary and conclusions are included here, the full thesis is available at the URL listed above.

  9. New View of Distant Galaxy Reveals Furious Star Formation

    NASA Astrophysics Data System (ADS)

    2007-12-01

    A furious rate of star formation discovered in a distant galaxy shows that galaxies in the early Universe developed either much faster or in a different way from what astronomers have thought. "This galaxy is forming stars at an incredible rate," said Wei-Hao Wang, an astronomer at the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. The galaxy, Wang said, is forming the equivalent of 4,000 Suns a year. This is a thousand times more violent than our own Milky Way Galaxy. Location of Distant Galaxy Visible-light, left (from HST) and Infrared, right, (from Spitzer) Images: Circles indicate location of GOODS 850-5. CREDIT: Wang et al., STScI, Spitzer, NASA, NRAO/AUI/NSF Click on image for high-resolution file (1 MB) The galaxy, called GOODS 850-5, is 12 billion light-years from Earth, and thus is seen as it was only about 1.5 billion years after the Big Bang. Wang and his colleagues observed it using the Smithsonian Astrophysical Observatory's Submillimeter Array (SMA) on Mauna Kea in Hawaii. Young stars in the galaxy were enshrouded in dust that was heated by the stars and radiated infrared light strongly. Because of the galaxy's great distance from Earth, the infrared light waves have been stretched out to submillimeter-length radio waves, which are seen by the SMA. The waves were stretched or "redshifted," as astronomers say, by the ongoing expansion of the Universe. "This evidence for prolific star formation is hidden by the dust from visible-light telescopes," Wang explained. The dust, in turn, was formed from heavy elements that had to be built up in the cores of earlier stars. This indicates, Wang said, that significant numbers of stars already had formed, then spewed those heavy elements into interstellar space through supernova explosions and stellar winds. "Seeing the radiation from this heated dust revealed star formation we could have found in no other way," Wang said. Similar dusty galaxies in the early Universe may contain most of the

  10. TIME-VARYING DYNAMICAL STAR FORMATION RATE

    SciTech Connect

    Lee, Eve J.; Chang, Philip; Murray, Norman

    2015-02-10

    We present numerical evidence of dynamic star formation in which the accreted stellar mass grows superlinearly with time, roughly as t {sup 2}. We perform simulations of star formation in self-gravitating hydrodynamic and magnetohydrodynamic turbulence that is continuously driven. By turning the self-gravity of the gas in the simulations on or off, we demonstrate that self-gravity is the dominant physical effect setting the mass accretion rate at early times before feedback effects take over, contrary to theories of turbulence-regulated star formation. We find that gravitational collapse steepens the density profile around stars, generating the power-law tail on what is otherwise a lognormal density probability distribution function. Furthermore, we find turbulent velocity profiles to flatten inside collapsing regions, altering the size-line width relation. This local flattening reflects enhancements of turbulent velocity on small scales, as verified by changes to the velocity power spectra. Our results indicate that gas self-gravity dynamically alters both density and velocity structures in clouds, giving rise to a time-varying star formation rate. We find that a substantial fraction of the gas that forms stars arrives via low-density flows, as opposed to accreting through high-density filaments.

  11. Basin Formation and Cratering on Mercury Revealed by MESSENGER

    NASA Astrophysics Data System (ADS)

    Chapman, C. R.; Fassett, C.; Marchi, S.; Merline, W. J.; Ostrach, L. R.; Prockter, L. M.

    2015-12-01

    Mercury has been bombarded by asteroids and comets throughout its history. The resulting craters and basins are the dominant topographic features on the planet. Although visible basins contain some of the most interesting tectonic features, plains, and evidence of vertical stratigraphy, they fall far short of saturating the surface. Nevertheless, Mercury has a greater spatial density of peak-ring basins and protobasins than any other Solar System body, partly because these morphologies begin at smaller sizes than on most bodies. Cratering at approximately three times the cratering rate on the Moon, combined with likely plains-forming volcanism, prevents recognition of surface features older than 4.0 to 4.1 Ga. Severe losses of craters <50 km in diameter (<20 km in some places) are ascribed to extensive formation of intercrater plains. Estimates of the cratering chronology of Mercury suggest that most plains formation ended about 3.6 to 3.7 Ga, though activity has continued in a few small regions until much more recently (e.g., inside the Rachmaninoff basin). Mercury, compared with other terrestrial bodies, is struck by projectiles impacting at much higher velocities, which is probably responsible for the formation of abundant secondary craters that dominate the numbers of craters <10 km diameter on older plains surfaces. The history of high-velocity bombardment has resulted in the production of abundant impact melts and has churned and processed the regolith, and eroded older topography, more thoroughly than on other Solar System bodies. Although the possible role of Mercury-specific impactors ("vulcanoids") cannot be excluded, imaging searches by MESSENGER have revealed no remaining vulcanoids and no other evidence suggests that Mercury has been bombarded by anything other than the same populations of asteroids and comets that have impacted the Moon and other terrestrial planets from the end of the period of heavy bombardment 3.8 to 3.9 Ga to the present.

  12. The Absolute Rate of LGRB Formation

    NASA Astrophysics Data System (ADS)

    Graham, J. F.; Schady, P.

    2016-06-01

    We estimate the long-duration gamma-ray burst (LGRB) progenitor rate using our recent work on the effects of environmental metallically on LGRB formation in concert with supernovae (SNe) statistics via an approach patterned loosely off the Drake equation. Beginning with the cosmic star formation history, we consider the expected number of broad-line Type Ic events (the SNe type associated with LGRBs) that are in low-metallicity host environments adjusted by the contribution of high-metallicity host environments at a much reduced rate. We then compare this estimate to the observed LGRB rate corrected for instrumental selection effects to provide a combined estimate of the efficiency fraction of these progenitors to produce LGRBs and the fraction of which are beamed in our direction. From this we estimate that an aligned LGRB occurs for approximately every 4000 ± 2000 low-metallically broad-lined SNe Ic. Therefore, if one assumes a semi-nominal beaming factor of 100, then only about one such supernova out of 40 produce an LGRB. Finally, we propose an off-axis LGRB search strategy of targeting only broad-line Type Ic events that occur in low-metallicity hosts for radio observation.

  13. ANALYTICAL STAR FORMATION RATE FROM GRAVOTURBULENT FRAGMENTATION

    SciTech Connect

    Hennebelle, Patrick; Chabrier, Gilles

    2011-12-20

    We present an analytical determination of the star formation rate (SFR) in molecular clouds, based on a time-dependent extension of our analytical theory of the stellar initial mass function. The theory yields SFRs in good agreement with observations, suggesting that turbulence is the dominant, initial process responsible for star formation. In contrast to previous SFR theories, the present one does not invoke an ad hoc density threshold for star formation; instead, the SFR continuously increases with gas density, naturally yielding two different characteristic regimes, thus two different slopes in the SFR versus gas density relationship, in agreement with observational determinations. Besides the complete SFR derivation, we also provide a simplified expression, which reproduces the complete calculations reasonably well and can easily be used for quick determinations of SFRs in cloud environments. A key property at the heart of both our complete and simplified theory is that the SFR involves a density-dependent dynamical time, characteristic of each collapsing (prestellar) overdense region in the cloud, instead of one single mean or critical freefall timescale. Unfortunately, the SFR also depends on some ill-determined parameters, such as the core-to-star mass conversion efficiency and the crossing timescale. Although we provide estimates for these parameters, their uncertainty hampers a precise quantitative determination of the SFR, within less than a factor of a few.

  14. Circulating protein synthesis rates reveal skeletal muscle proteome dynamics.

    PubMed

    Shankaran, Mahalakshmi; King, Chelsea L; Angel, Thomas E; Holmes, William E; Li, Kelvin W; Colangelo, Marc; Price, John C; Turner, Scott M; Bell, Christopher; Hamilton, Karyn L; Miller, Benjamin F; Hellerstein, Marc K

    2016-01-01

    Here, we have described and validated a strategy for monitoring skeletal muscle protein synthesis rates in rodents and humans over days or weeks from blood samples. We based this approach on label incorporation into proteins that are synthesized specifically in skeletal muscle and escape into the circulation. Heavy water labeling combined with sensitive tandem mass spectrometric analysis allowed integrated synthesis rates of proteins in muscle tissue across the proteome to be measured over several weeks. Fractional synthesis rate (FSR) of plasma creatine kinase M-type (CK-M) and carbonic anhydrase 3 (CA-3) in the blood, more than 90% of which is derived from skeletal muscle, correlated closely with FSR of CK-M, CA-3, and other proteins of various ontologies in skeletal muscle tissue in both rodents and humans. Protein synthesis rates across the muscle proteome generally changed in a coordinate manner in response to a sprint interval exercise training regimen in humans and to denervation or clenbuterol treatment in rodents. FSR of plasma CK-M and CA-3 revealed changes and interindividual differences in muscle tissue proteome dynamics. In human subjects, sprint interval training primarily stimulated synthesis of structural and glycolytic proteins. Together, our results indicate that this approach provides a virtual biopsy, sensitively revealing individualized changes in proteome-wide synthesis rates in skeletal muscle without a muscle biopsy. Accordingly, this approach has potential applications for the diagnosis, management, and treatment of muscle disorders. PMID:26657858

  15. Circulating protein synthesis rates reveal skeletal muscle proteome dynamics

    PubMed Central

    Shankaran, Mahalakshmi; King, Chelsea L.; Angel, Thomas E.; Holmes, William E.; Li, Kelvin W.; Colangelo, Marc; Price, John C.; Turner, Scott M.; Bell, Christopher; Hamilton, Karyn L.; Miller, Benjamin F.; Hellerstein, Marc K.

    2015-01-01

    Here, we have described and validated a strategy for monitoring skeletal muscle protein synthesis rates in rodents and humans over days or weeks from blood samples. We based this approach on label incorporation into proteins that are synthesized specifically in skeletal muscle and escape into the circulation. Heavy water labeling combined with sensitive tandem mass spectrometric analysis allowed integrated synthesis rates of proteins in muscle tissue across the proteome to be measured over several weeks. Fractional synthesis rate (FSR) of plasma creatine kinase M-type (CK-M) and carbonic anhydrase 3 (CA-3) in the blood, more than 90% of which is derived from skeletal muscle, correlated closely with FSR of CK-M, CA-3, and other proteins of various ontologies in skeletal muscle tissue in both rodents and humans. Protein synthesis rates across the muscle proteome generally changed in a coordinate manner in response to a sprint interval exercise training regimen in humans and to denervation or clenbuterol treatment in rodents. FSR of plasma CK-M and CA-3 revealed changes and interindividual differences in muscle tissue proteome dynamics. In human subjects, sprint interval training primarily stimulated synthesis of structural and glycolytic proteins. Together, our results indicate that this approach provides a virtual biopsy, sensitively revealing individualized changes in proteome-wide synthesis rates in skeletal muscle without a muscle biopsy. Accordingly, this approach has potential applications for the diagnosis, management, and treatment of muscle disorders. PMID:26657858

  16. Towards universal hybrid star formation rate estimators

    NASA Astrophysics Data System (ADS)

    Boquien, M.; Kennicutt, R.; Calzetti, D.; Dale, D.; Galametz, M.; Sauvage, M.; Croxall, K.; Draine, B.; Kirkpatrick, A.; Kumari, N.; Hunt, L.; De Looze, I.; Pellegrini, E.; Relaño, M.; Smith, J.-D.; Tabatabaei, F.

    2016-06-01

    Context. To compute the star formation rate (SFR) of galaxies from the rest-frame ultraviolet (UV), it is essential to take the obscuration by dust into account. To do so, one of the most popular methods consists in combining the UV with the emission from the dust itself in the infrared (IR). Yet, different studies have derived different estimators, showing that no such hybrid estimator is truly universal. Aims: In this paper we aim at understanding and quantifying what physical processes fundamentally drive the variations between different hybrid estimators. In so doing, we aim at deriving new universal UV+IR hybrid estimators to correct the UV for dust attenuation at local and global scales, taking the intrinsic physical properties of galaxies into account. Methods: We use the CIGALE code to model the spatially resolved far-UV to far-IR spectral energy distributions of eight nearby star-forming galaxies drawn from the KINGFISH sample. This allows us to determine their local physical properties, and in particular their UV attenuation, average SFR, average specific SFR (sSFR), and their stellar mass. We then examine how hybrid estimators depend on said properties. Results: We find that hybrid UV+IR estimators strongly depend on the stellar mass surface density (in particular at 70 μm and 100 μm) and on the sSFR (in particular at 24 μm and the total infrared). Consequently, the IR scaling coefficients for UV obscuration can vary by almost an order of magnitude: from 1.55 to 13.45 at 24 μm for instance. This result contrasts with other groups who found relatively constant coefficients with small deviations. We exploit these variations to construct a new class of adaptative hybrid estimators based on observed UV to near-IR colours and near-IR luminosity densities per unit area. We find that they can reliably be extended to entire galaxies. Conclusions: The new estimators provide better estimates of attenuation-corrected UV emission than classical hybrid estimators

  17. TEMPRANILLO Reveals the Mesophyll as Crucial for Epidermal Trichome Formation.

    PubMed

    Matías-Hernández, Luis; Aguilar-Jaramillo, Andrea E; Osnato, Michela; Weinstain, Roy; Shani, Eilon; Suárez-López, Paula; Pelaz, Soraya

    2016-03-01

    Plant trichomes are defensive specialized epidermal cells. In all accepted models, the epidermis is the layer involved in trichome formation, a process controlled by gibberellins (GAs) in Arabidopsis rosette leaves. Indeed, GA activates a genetic cascade in the epidermis for trichome initiation. Here we report that TEMPRANILLO (TEM) genes negatively control trichome initiation not only from the epidermis but also from the leaf layer underneath the epidermis, the mesophyll. Plants over-expressing or reducing TEM specifically in the mesophyll, display lower or higher trichome numbers, respectively. We surprisingly found that fluorescently labeled GA3 accumulates exclusively in the mesophyll of leaves, but not in the epidermis, and that TEM reduces its accumulation and the expression of several newly identified GA transporters. This strongly suggests that TEM plays an essential role, not only in GA biosynthesis, but also in regulating GA distribution in the mesophyll, which in turn directs epidermal trichome formation. Moreover, we show that TEM also acts as a link between GA and cytokinin signaling in the epidermis by negatively regulating downstream genes of both trichome formation pathways. Overall, these results call for a re-evaluation of the present theories of trichome formation as they reveal mesophyll essential during epidermal trichome initiation. PMID:26802039

  18. Stochastic heart-rate model can reveal pathologic cardiac dynamics

    NASA Astrophysics Data System (ADS)

    Kuusela, Tom

    2004-03-01

    A simple one-dimensional Langevin-type stochastic difference equation can simulate the heart-rate fluctuations in a time scale from minutes to hours. The model consists of a deterministic nonlinear part and a stochastic part typical of Gaussian noise, and both parts can be directly determined from measured heart-rate data. Data from healthy subjects typically exhibit the deterministic part with two or more stable fixed points. Studies of 15 congestive heart-failure subjects reveal that the deterministic part of pathologic heart dynamics has no clear stable fixed points. Direct simulations of the stochastic model for normal and pathologic cases can produce statistical parameters similar to those of real subjects. Results directly indicate that pathologic situations simplify the heart-rate control system.

  19. Rating Format Effects on Rater Agreement and Reliability.

    ERIC Educational Resources Information Center

    Littlefield, John H.; Troendle, G. Roger

    This study compares intra- and inter-rater agreement and reliability when using three different rating form formats to assess the same stimuli. One format requests assessment by marking detailed criteria without an overall judgement; the second format requests only an overall judgement without the use of detailed criteria; and the third format…

  20. Inclination Dependence of Estimated Galaxy Masses and Star Formation Rates

    NASA Astrophysics Data System (ADS)

    Hernandez, Betsy; Maller, Ariyeh; McKernan, Barry; Ford, Saavik

    2016-01-01

    We examine the inclination dependence of inferred star formation rates and galaxy mass estimates in the Sloan Digital Sky Survey by combining the disk/bulge de-convolved catalog of Simard et al 2011 with stellar mass estimates catalog of Mendel et al 2014 and star formation rates measured from spectra by Brinchmann et al 2004. We know that optical star formation indicators are reddened by dust, but calculated star formation rates and stellar mass estimates should account for this. However, we find that face-on galaxies have a higher calculated average star formation rates than edge-on galaxies. We also find edge-on galaxies have ,on average, slightly smaller but similar estimated masses to face-on galaxies, suggesting that there are issues with the applied dust corrections for both models.

  1. Recovering the Star Formation Rate in the Solar Neighborhood

    NASA Astrophysics Data System (ADS)

    Cignoni, M.; Degl'Innocenti, S.; Moroni, P. G. P.; Shore, S. N.

    2007-11-01

    This paper develops a method for obtaining the star formation histories of a mixed, resolved population through the use of color-magnitude diagrams (CMDs). The method is applied to the derivation of the local star formation rate, analyzing the observations of the Hipparcos satellite through a comparison with synthetic CMDs computed for different star formation histories with an updated stellar evolution library. Parallax and photometric uncertainties are included explicitly and corrected using the Bayesian Richardson-Lucy algorithm. We find that the solar neighborhood star formation rate has a characteristic timescale for variation of about 6 Gyr, with a maximum activity close to 3 Gyr ago.

  2. Identifying inhibitors of hydrate formation rate with viscometric experiments

    SciTech Connect

    Kalbus, J.S.; Christiansen, R.L.; Sloan, D. Jr.

    1995-12-31

    Inhibiting the rate of hydrate formation with low concentration additives is an economically and environmentally attractive alternative to prevention of hydrates with large doses of methanol. Here, a method for screening possible rate inhibitors is described. In the method, a viscometer is used to follow the development of hydrate formation for water-THF solutions and for water-gas solutions at conditions favoring hydrate formation. The method was applied to about 30 different chemicals, plus binary combinations of many of these chemicals. The best chemical additives included BASF F-127, Mirawet ASC, Surfynol-465, sodium dodecyl sulfate(SDS), Mirataine CBS with polyvinylpyrrolidone(PVP), and SDS with PVP.

  3. Star formation rates of spiral galaxies in the Cosmic Web

    NASA Astrophysics Data System (ADS)

    Alpaslan, Mehmet; Marcum, Pamela M.; Galaxy And Mass Assembly (GAMA)

    2016-01-01

    We look for shifts in stellar mass and star formation rate along filaments in the cosmic web by examining the stellar masses and UV-derived star formation rates of 1,799 ungrouped and unpaired spiral galaxies from the Galaxy And Mass Assembly (GAMA) survey that reside in filaments. We devise multiple distance metrics to characterise the complex geometry of filaments, and find that galaxies closer to the orthogonal core of a filament have higher stellar masses than their counterparts near the periphery of filaments, on the edges of voids. We also find that these peripheral galaxies have higher specific star formations at a given mass. Our results suggest a model in which gas accretion from voids onto filaments is primarily in an orthogonal direction. While the star formation rates of spiral galaxies in filaments are susceptible to their locations, we find that the global star formation rates of galaxies in different large scale environments are similar to each other. The primary discriminant in star formation rates is therefore the stellar mass of each spiral galaxy, as opposed to its large scale environment.

  4. Recovering the star formation rate in the solar neighborhood

    NASA Astrophysics Data System (ADS)

    Cignoni, M.; Degl'Innocenti, S.; Prada Moroni, P. G.; Shore, S. N.

    2006-12-01

    Aims.This paper develops a method for obtaining the star formation histories of a mixed, resolved population through the use of color-magnitude diagrams (CMDs). The method provides insight into the local star formation rate, analyzing the observations of the Hipparcos satellite through a comparison with synthetic CMDs computed for different histories with an updated stellar evolution library. Methods: .Parallax and photometric uncertainties are included explicitly and corrected using the Bayesian Richardson-Lucy algorithm. We first describe our verification studies using artificial data sets. From this sensitivity study, the critical factors determining the success of a recovery for a known star formation rate are a partial knowledge of the IMF and the age-metallicity relation, and sample contamination by clusters and moving groups (special populations whose histories are different than that of the whole sample). Unresolved binaries are less important impediments. We highlight how these limit the method. Results: .For the real field sample, complete to MV < 3.5, we find that the solar neighborhood star formation rate has a characteristic timescale for variation of about 6 Gyr, with a maximum activity close to 3 Gyr ago. The similarity of this finding with column integrated star formation rates may indicate a global origin, possibly a collision with a satellite galaxy. We also discuss applications of this technique to general photometric surveys of other complex systems (e.g. Local Group dwarf galaxies) where the distances are well known.

  5. Star formation rates and abundance gradients in disk galaxies

    NASA Technical Reports Server (NTRS)

    Wyse, Rosemary F. G.; Silk, Joseph

    1989-01-01

    Analytic models for the evolution of disk galaxies are presented, placing special emphasis on the radial properties. These models are straightforward extensions of the original Schmidt (1959, 1963) models, with a dependence of star formation rate on gas density. The models provide successful descriptions of several measures of galactic disk evolution, including solar neighborhood chemical evolution, the presence and amplitude of metallicity and color gradients in disk galaxies, and the global rates of star formation in disk galaxies, and aid in the understanding of the apparent connection between young and old stellar populations in spiral galaxies.

  6. The star formation rate density from z = 1 to 6

    NASA Astrophysics Data System (ADS)

    Rowan-Robinson, Michael; Oliver, Seb; Wang, Lingyu; Farrah, Duncan; Clements, David L.; Gruppioni, Carlotta; Marchetti, Lucia; Rigopoulou, Dimitra; Vaccari, Mattia

    2016-09-01

    We use 3035 Herschel-SPIRE 500 μm sources from 20.3 deg2 of sky in the HerMES Lockman, ES1 and XMM-LSS areas to estimate the star formation rate density at z = 0-6. 500 μm sources are associated first with 350 and 250 μm sources, and then with Spitzer 24 μm sources from the SWIRE photometric redshift catalogue. The infrared and submillimetre data are fitted with a set of radiative-transfer templates corresponding to cirrus (quiescent) and starburst galaxies. Lensing candidates are removed via a set of colour-colour and colour-redshift constraints. Star formation rates are found to extend from <1 to 20 000 M⊙ yr-1. Such high values were also seen in the all-sky IRAS Faint Source Survey. Star formation rate functions are derived in a series of redshift bins from 0 to 6, combined with earlier far-infrared estimates, where available, and fitted with a Saunders et al (1990) functional form. The star formation rate density as a function of redshift is derived and compared with other estimates. There is reasonable agreement with both infrared and ultraviolet estimates for z < 3, but we find higher star formation rate densities than ultraviolet estimates at z = 3-6. Given the considerable uncertainties in the submillimetre estimates, we cannot rule out the possibility that the ultraviolet estimates are correct. But the possibility that the ultraviolet estimates have seriously underestimated the contribution of dust-shrouded star formation can also not be excluded.

  7. Generalised heart rate statistics reveal neurally mediated homeostasis transients

    NASA Astrophysics Data System (ADS)

    Makowiec, D.; Graff, B.; Miklaszewski, W.; Wejer, D.; Kaczkowska, A.; Budrejko, S.; Struzik, Z. R.

    2015-04-01

    Distributions of accelerations and decelerations, obtained from increments of heart rate recorded during a head-up tilt table (HUTT) test provide short-term characterization of the complex cardiovascular response to a rapid controlled dysregulation of homeostasis. A generalised statistic is proposed for evaluating the neural reflexes responsible for restoring the homeostatic dynamics. An evaluation of the effects on heart rate of the neural regulation involved in achieving homeostasis indicates a distinction between vasovagal patients and healthy subjects who are not susceptible to spontaneous fainting. A healthy cardiovascular response to the HUTT test is identified in the sympathetic tone appropriately punctuated by vagal activity.

  8. Star formation rates in luminous quasars at 2 < z < 3

    NASA Astrophysics Data System (ADS)

    Harris, Kathryn; Farrah, Duncan; Schulz, Bernhard; Hatziminaoglou, Evanthia; Viero, Marco; Anderson, Nick; Béthermin, Matthieu; Chapman, Scott; Clements, David L.; Cooray, Asantha; Efstathiou, Andreas; Feltre, Anne; Hurley, Peter; Ibar, Eduardo; Lacy, Mark; Oliver, Sebastian; Page, Mathew J.; Pérez-Fournon, Ismael; Petty, Sara M.; Pitchford, Lura K.; Rigopoulou, Dimitra; Scott, Douglas; Symeonidis, Myrto; Vieira, Joaquin; Wang, Lingyu

    2016-04-01

    We investigate the relation between star formation rates (dot{{M}}_s) and AGN properties in optically selected type 1 quasars at 2 < z < 3 using data from Herschel and the SDSS. We find that dot{{M}}_s remains approximately constant with redshift, at 300 ± 100 M⊙ yr-1. Conversely, dot{{M}}_s increases with AGN luminosity, up to a maximum of ˜ 600 M⊙ yr-1, and with C IV FWHM. In context with previous results, this is consistent with a relation between dot{{M}}_s and black hole accretion rate (dot{{M}}_{bh}) existing in only parts of the z-dot{{M}}s-dot{{M}}_{bh} plane, dependent on the free gas fraction, the trigger for activity, and the processes that may quench star formation. The relations between dot{{M}}_s and both AGN luminosity and C IV FWHM are consistent with star formation rates in quasars scaling with black hole mass, though we cannot rule out a separate relation with black hole accretion rate. Star formation rates are observed to decline with increasing C IV equivalent width. This decline can be partially explained via the Baldwin effect, but may have an additional contribution from one or more of three factors; Mi is not a linear tracer of L2500, the Baldwin effect changes form at high AGN luminosities, and high C IV EW values signpost a change in the relation between dot{{M}}_s and dot{{M}}_{bh}. Finally, there is no strong relation between dot{{M}}_s and Eddington ratio, or the asymmetry of the C IV line. The former suggests that star formation rates do not scale with how efficiently the black hole is accreting, while the latter is consistent with C IV asymmetries arising from orientation effects.

  9. Mechanisms of amyloid formation revealed by solution NMR

    PubMed Central

    Karamanos, Theodoros K.; Kalverda, Arnout P.; Thompson, Gary S.; Radford, Sheena E.

    2015-01-01

    Amyloid fibrils are proteinaceous elongated aggregates involved in more than fifty human diseases. Recent advances in electron microscopy and solid state NMR have allowed the characterization of fibril structures to different extents of refinement. However, structural details about the mechanism of fibril formation remain relatively poorly defined. This is mainly due to the complex, heterogeneous and transient nature of the species responsible for assembly; properties that make them difficult to detect and characterize in structural detail using biophysical techniques. The ability of solution NMR spectroscopy to investigate exchange between multiple protein states, to characterize transient and low-population species, and to study high molecular weight assemblies, render NMR an invaluable technique for studies of amyloid assembly. In this article we review state-of-the-art solution NMR methods for investigations of: (a) protein dynamics that lead to the formation of aggregation-prone species; (b) amyloidogenic intrinsically disordered proteins; and (c) protein–protein interactions on pathway to fibril formation. Together, these topics highlight the power and potential of NMR to provide atomic level information about the molecular mechanisms of one of the most fascinating problems in structural biology. PMID:26282197

  10. THE COSMIC CORE-COLLAPSE SUPERNOVA RATE DOES NOT MATCH THE MASSIVE-STAR FORMATION RATE

    SciTech Connect

    Horiuchi, Shunsaku; Beacom, John F.; Kochanek, Christopher S.; Stanek, K. Z.; Thompson, Todd A.; Prieto, Jose L.

    2011-09-10

    We identify a 'supernova rate problem': the measured cosmic core-collapse supernova rate is a factor of {approx}2 smaller (with significance {approx}2{sigma}) than that predicted from the measured cosmic massive-star formation rate. The comparison is critical for topics from galaxy evolution and enrichment to the abundance of neutron stars and black holes. We systematically explore possible resolutions. The accuracy and precision of the star formation rate data and conversion to the supernova rate are well supported, and proposed changes would have far-reaching consequences. The dominant effect is likely that many supernovae are missed because they are either optically dim (low-luminosity) or dark, whether intrinsically or due to obscuration. We investigate supernovae too dim to have been discovered in cosmic surveys by a detailed study of all supernova discoveries in the local volume. If possible supernova impostors are included, then dim supernovae are common enough by fraction to solve the supernova rate problem. If they are not included, then the rate of dark core collapses is likely substantial. Other alternatives are that there are surprising changes in our understanding of star formation or supernova rates, including that supernovae form differently in small galaxies than in normal galaxies. These possibilities can be distinguished by upcoming supernova surveys, star formation measurements, searches for disappearing massive stars, and measurements of supernova neutrinos.

  11. Mechanistic studies of carbonate macrocyclization: Rates of carbonate bond formation

    SciTech Connect

    Aquino, E.; Brittain, W.J.; Brunelle, D.J.

    1993-12-31

    High yields of cyclic oligomeric carbonates can be prepared using an amine-catalyzed reaction of bisphenol A-bischloroformate. The authors have studied the kinetics of this carbonate macrocyclization by the isolated study of key chemical events. Using stopped-flow FT-IR spectroscopy, it was found that the rate of carbonate formation between the intermediate acyl ammonium salt (1) and 4-isopropylphenol (4-IPP) is the same for tributylamine, triethylamine and diethylmethylamine. Previously, it was found that conversion of 1 to urethane was also insensitive to amine structure while the formation of 1 is profoundly dependent on amine structure.

  12. Connecting Galaxies, Halos, and Star Formation Rates Across Cosmic Time

    SciTech Connect

    Conroy, Charlie; Wechsler, Risa H.

    2008-06-02

    A simple, observationally-motivated model is presented for understanding how halo masses, galaxy stellar masses, and star formation rates are related, and how these relations evolve with time. The relation between halo mass and galaxy stellar mass is determined by matching the observed spatial abundance of galaxies to the expected spatial abundance of halos at multiple epochs--i.e. more massive galaxies are assigned to more massive halos at each epoch. This 'abundance matching' technique has been shown previously to reproduce the observed luminosity- and scale-dependence of galaxy clustering over a range of epochs. Halos at different epochs are connected by halo mass accretion histories estimated from N-body simulations. The halo-galaxy connection at fixed epochs in conjunction with the connection between halos across time provides a connection between observed galaxies across time. With approximations for the impact of merging and accretion on the growth of galaxies, one can then directly infer the star formation histories of galaxies as a function of stellar and halo mass. This model is tuned to match both the observed evolution of the stellar mass function and the normalization of the observed star formation rate--stellar mass relation to z {approx} 1. The data demands, for example, that the star formation rate density is dominated by galaxies with M{sub star} {approx} 10{sup 10.0-10.5} M{sub {circle_dot}} from 0 < z < 1, and that such galaxies over these epochs reside in halos with M{sub vir} {approx} 10{sup 11.5-12.5} M{sub {circle_dot}}. The star formation rate--halo mass relation is approximately Gaussian over the range 0 < z < 1 with a mildly evolving mean and normalization. This model is then used to shed light on a number of issues, including (1) a clarification of 'downsizing', (2) the lack of a sharp characteristic halo mass at which star formation is truncated, and (3) the dominance of star formation over merging to the stellar build-up of galaxies

  13. Bone Formation Rate in Experimental Disuse Osteoporosis in Monkeys

    NASA Technical Reports Server (NTRS)

    Cann, Christopher; Young, Donald R.

    1976-01-01

    Specific mechanisms underlying weightless and hypodynamic bone loss are obscure. A principal relationship which must be affected is the balance between bone formation and bone resorption rates. In order to better define the influence of those parameters on bone loss, and also to develop measurements in other species as a useful adjunct to human research, studies were undertaken with experimental monkeys. Tests were conducted with a total of 6 adult male monkeys, weighing 10-13 kg, and approximately 10-12 yrs. of age to evaluate specifically bone formation rate during the development of disuse osteoporosis and osteopenia. Three animals were restrained in a semi-recumbent position for six months; three animals served as normal caged controls. Food intake (Purina) was held relatively constant at 200g/day for each animal. Using a Norland Bone Mineral Analyzer, bone mineral losses of 3.5 to 6% were seen in the mid-shaft of the tibia and in the distal radius. Bone loss was confirmed radiographically, with observation of thinning of the proximal tibial cortex and trabeculae in the calcaneus. Bone formation rate was determined using standard Ca-47 kinetics under metabolic balance conditions. After six months of restraint, accretion was 7.2-13.2 mg Ca/kg/day, compared to 3.2-4.1 mg Ca/kg/day in caged controls and 3-8 mg Ca/kg/day in normal adult humans. Fecal and urine calcium was 25-40% higher in restrained animals than in controls. Dietary calcium absorption decreases during restraint, and calcium turnover increases, implying a rise in bone resorption rate concommitant with the observed rise in bone accretion rate. Further studies dealing specifically with bone resorption are underway to define this more fully.

  14. VLBA Reveals Formation Region of Giant Cosmic Jet

    NASA Astrophysics Data System (ADS)

    1999-10-01

    Astronomers have gained their first glimpse of the mysterious region near a black hole at the heart of a distant galaxy, where a powerful stream of subatomic particles spewing outward at nearly the speed of light is formed into a beam, or jet, that then goes nearly straight for thousands of light-years. The astronomers used radio telescopes in Europe and the U.S., including the National Science Foundation's (NSF) Very Long Baseline Array (VLBA) to make the most detailed images ever of the center of the galaxy M87, some 50 million light-years away. "This is the first time anyone has seen the region in which a cosmic jet is formed into a narrow beam," said Bill Junor of the University of New Mexico, in Albuquerque. "We had always speculated that the jet had to be made by some mechanism relatively near the black hole, but as we looked closer and closer to the center, we kept seeing an already-formed beam. That was becoming embarrassing, because we were running out of places to put the formation mechanism that we knew had to be there." Junor, along with John Biretta and Mario Livio of the Space Telescope Science Institute, in Baltimore, MD, now have shown that M87's jet is formed within a few tenths of a light-year of the galaxy's core, presumed to be a black hole three billion times more massive than the sun. In the formation region, the jet is seen opening widely, at an angle of about 60 degrees, nearest the black hole, but is squeezed down to only 6 degrees a few light-years away. "The 60-degree angle of the inner part of M87's jet is the widest such angle yet seen in any jet in the universe," said Junor. "We found this by being able to see the jet to within a few hundredths of a light-year of the galaxy's core -- an unprecedented level of detail." The scientists reported their findings in the October 28 issue of the journal Nature. At the center of M87, material being drawn inward by the strong gravitation of the black hole is formed into a rapidly-spinning flat

  15. Oman metamorphic sole formation reveals early subduction dynamics

    NASA Astrophysics Data System (ADS)

    Soret, Mathieu; Agard, Philippe; Dubacq, Benoît; Plunder, Alexis; Ildefonse, Benoît; Yamato, Philippe; Prigent, Cécile

    2016-04-01

    Metamorphic soles correspond to m to ~500m thick tectonic slices welded beneath most of the large-scale ophiolites. They typically show a steep inverted metamorphic structure where the pressure and temperature conditions of crystallization increase upward (from 500±100°C at 0.5±0.2 GPa to 800±100°C at 1.0±0.2 GPa), with isograds subparallel to the contact with the overlying ophiolitic peridotite. The proportion of mafic rocks in metamorphic soles also increases from the bottom (meta-sediments rich) to the top (approaching the ophiolite peridotites). These soles are interpreted as the result of heat transfer from the incipient mantle wedge toward the nascent slab (associated with large-scale fluid transfer and possible shear heating) during the first My of intra-oceanic subduction (as indicated by radiometric ages). Metamorphic soles provide therefore major constraints on early subduction dynamics (i.e., thermal structure, fluid migration and rheology along the nascent slab interface). We present a detailed structural and petrological study of the metamorphic sole from 4 major cross-sections along the Oman ophiolite. We show precise pressure-temperature estimates obtained by pseudosection modelling and EBSD measurements performed on both the garnet-bearing and garnet-free high-grade sole. Results allow quantification of the micro-scale deformation and highlight differences in pressure-temperature-deformation conditions between the 4 different locations, showing that the inverted metamorphic gradient through the sole is not continuous in all locations. Based on these new constraints, we suggest a new tectonic-petrological model for the formation of metamorphic soles below ophiolites. This model involves the stacking of several homogeneous slivers of oceanic crust leading to the present-day structure of the sole. In this view, these thrusts are the result of rheological contrasts between the sole and the peridotite as the plate interface progressively cools down

  16. The Fundamental Plane of star formation in galaxies revealed by the EAGLE hydrodynamical simulations

    NASA Astrophysics Data System (ADS)

    Lagos, Claudia del P.; Theuns, Tom; Schaye, Joop; Furlong, Michelle; Bower, Richard G.; Schaller, Matthieu; Crain, Robert A.; Trayford, James W.; Matthee, Jorryt

    2016-07-01

    We investigate correlations between different physical properties of star-forming galaxies in the `Evolution and Assembly of GaLaxies and their Environments' (EAGLE) cosmological hydrodynamical simulation suite over the redshift range 0 ≤ z ≤ 4.5. A principal component analysis reveals that neutral gas fraction (fgas,neutral), stellar mass (Mstellar) and star formation rate (SFR) account for most of the variance seen in the population, with galaxies tracing a two-dimensional, nearly flat, surface in the three-dimensional space of fgas, neutral-Mstellar-SFR with little scatter. The location of this plane varies little with redshift, whereas galaxies themselves move along the plane as their fgas, neutral and SFR drop with redshift. The positions of galaxies along the plane are highly correlated with gas metallicity. The metallicity can therefore be robustly predicted from fgas, neutral, or from the Mstellar and SFR. We argue that the appearance of this `Fundamental Plane of star formation' is a consequence of self-regulation, with the plane's curvature set by the dependence of the SFR on gas density and metallicity. We analyse a large compilation of observations spanning the redshift range 0 ≲ z ≲ 3, and find that such a plane is also present in the data. The properties of the observed Fundamental Plane of star formation are in good agreement with EAGLE's predictions.

  17. Predicting secondary organic aerosol formation rates in southeast Texas

    NASA Astrophysics Data System (ADS)

    Russell, Matthew; Allen, David T.

    2005-04-01

    Rates of secondary organic aerosol (SOA) formation, due to the reactions of aromatics and monoterpenes, were estimated for southeast Texas by incorporating a modified version of the Statewide Air Pollution Research Center's chemical mechanism (SAPRC99) into the Comprehensive Air Quality Model with extensions (CAMx version 3.10). The model included explicit representation of the reactions of five SOA precursors (α-pinene, β-pinene, sabinene, d-limonene, and Δ3-carene). Reactions of each SOA precursor with O3, OH radical, and NO3 radical were included. The model also included separate reactions for low- and high-SOA-yield aromatic groups with the OH radical. SOA yields in the mechanisms were estimated using compound-specific yield information (ΔSOA/ΔHC) derived from smog chamber experiments conducted by J. R. Odum and colleagues and R. J. Griffin and colleagues. The form of the SOA yield model was based on the work of J. R. Odum and colleagues and is a function of existing organic aerosol concentrations. Existing organic aerosol concentrations were estimated on the basis of ambient measurements of total organic carbon in southeast Texas. The reactions of monoterpenes (predominantly α-pinene and β-pinene) with ozone led to the most regional SOA formation, followed by monoterpenes with the nitrate radical. Aromatic-OH reactions led to less regional SOA formation compared to monoterpenes; however, this formation occurs close to the urban and industrial areas of Houston. In contrast, SOA formation due to the reactions of monoterpenes occurred in the forested areas north of the urban area. The results of this study are in qualitative agreement with estimates of SOA formation based on ambient data from the same time period.

  18. CONNECTING GALAXIES, HALOS, AND STAR FORMATION RATES ACROSS COSMIC TIME

    SciTech Connect

    Conroy, Charlie; Wechsler, Risa H.

    2009-05-01

    A simple, observationally motivated model is presented for understanding how halo masses, galaxy stellar masses, and star formation rates are related, and how these relations evolve with time. The relation between halo mass and galaxy stellar mass is determined by matching the observed spatial abundance of galaxies to the expected spatial abundance of halos at multiple epochs, i.e., more massive galaxies are assigned to more massive halos at each epoch. This 'abundance matching' technique has been shown previously to reproduce the observed luminosity and scale dependence of galaxy clustering over a range of epochs. Halos at different epochs are connected by halo mass accretion histories estimated from N-body simulations. The halo-galaxy connection at fixed epochs in conjunction with the connection between halos across time provides a connection between observed galaxies across time. With approximations for the impact of merging and accretion on the growth of galaxies, one can then directly infer the star formation histories of galaxies as a function of stellar and halo mass. This model is tuned to match both the observed evolution of the stellar mass function and the normalization of the observed star formation rate (SFR)-stellar mass relation to z {approx} 1. The data demands, for example, that the star formation rate density is dominated by galaxies with M {sub star} {approx} 10{sup 10.0-10.5} M {sub sun} from 0 < z < 1, and that such galaxies over these epochs reside in halos with M {sub vir} {approx} 10{sup 11.5-12.5} M {sub sun}. The SFR-halo mass relation is approximately Gaussian over the range 0 < z < 1 with a mildly evolving mean and normalization. This model is then used to shed light on a number of issues, including (1) a clarification of {sup d}ownsizing{sup ,} (2) the lack of a sharp characteristic halo mass at which star formation is truncated, and (3) the dominance of star formation over merging to the stellar buildup of galaxies with M {sub star

  19. Star Formation Laws, Rates, and Thresholds in Galaxies

    NASA Astrophysics Data System (ADS)

    Di Francesco, James

    2015-08-01

    It has been long recognized that stars form out of gas within the interstellar mediums of galaxies. Though earlier treatments focused on the relationship between star formation and the surface densities of available molecular gas in disks (e.g., the Kennicutt-Schmidt law), more recently the relevance of dense molecular gas within galaxies has become better appreciated. In this short review talk, I will provide an overview of how this shift in thinking in the last few years has occurred through observations. For example, strong correlations have been seen between the luminosities of HCN 1-0 (tracing dense gas) and infrared emission (tracing young stars) over nearly ten orders of magnitude. Also, the number of young stellar objects in nearby clouds seems to be related to the amount of mass in a cloud above a column density 'threshold' of Av ≈ 6 (surface density ≈ 120 Msun/pc2). Indeed, recent far-infrared/submillimetre continuum data of nearby molecular clouds from Herschel have shown strong links between star formation and filamentary structures in clouds above a critical mass per unit length of ~16 Msun/pc (Av ≈ 8), providing a possible origin of the observed 'threshold.' Also, the current star formation rate in a dense molecular cloud clump, as traced by the local number of Class 0 objects, appears to be highly correlated with the relative fraction of high column density material in the clump. Prospects for future exploration of star-formation thresholds will also be discussed.

  20. Measurement of the formation rate of muonic hydrogen molecules

    NASA Astrophysics Data System (ADS)

    Andreev, V. A.; Banks, T. I.; Carey, R. M.; Case, T. A.; Clayton, S. M.; Crowe, K. M.; Deutsch, J.; Egger, J.; Freedman, S. J.; Ganzha, V. A.; Gorringe, T.; Gray, F. E.; Hertzog, D. W.; Hildebrandt, M.; Kammel, P.; Kiburg, B.; Knaack, S.; Kravtsov, P. A.; Krivshich, A. G.; Lauss, B.; Lynch, K. R.; Maev, E. M.; Maev, O. E.; Mulhauser, F.; Petitjean, C.; Petrov, G. E.; Prieels, R.; Schapkin, G. N.; Semenchuk, G. G.; Soroka, M. A.; Tishchenko, V.; Vasilyev, A. A.; Vorobyov, A. A.; Vznuzdaev, M. E.; Winter, P.; MuCap Collaboration

    2015-05-01

    Background: The rate λpp μ characterizes the formation of p p μ molecules in collisions of muonic p μ atoms with hydrogen. In measurements of the basic weak muon capture reaction on the proton to determine the pseudoscalar coupling gP, capture occurs from both atomic and molecular states. Thus knowledge of λpp μ is required for a correct interpretation of these experiments. Purpose: Recently the MuCap experiment has measured the capture rate ΛS from the singlet p μ atom, employing a low-density active target to suppress p p μ formation [V. Andreev et al. (MuCap Collaboration), Phys. Rev. Lett. 110, 012504 (2013)], 10.1103/PhysRevLett.110.012504. Nevertheless, given the unprecedented precision of this experiment, the existing experimental knowledge in λpp μ had to be improved. Method: The MuCap experiment derived the weak capture rate from the muon disappearance rate in ultrapure hydrogen. By doping the hydrogen with 20 ppm of argon, a competing process to p p μ formation was introduced, which allowed the extraction of λpp μ from the observed time distribution of decay electrons. Results: The p p μ formation rate was measured as λpp μ=(2.01 ±0 .06stat±0 .03sys) ×106s-1 . This result updates the λpp μ value used in the abovementioned MuCap publication. Conclusions: The 2.5 × higher precision compared to earlier experiments, and the fact that the measurement was performed under nearly identical conditions as the main data taking, reduces the uncertainty induced by λpp μ to a minor contribution to the overall uncertainty of ΛS and gP, as determined in the MuCap experiment. Our final value for λpp μ shifts ΛS and gP by less than one-tenth of their respective uncertainties compared to our results published earlier.

  1. Rate of organic film formation and oxidation on aqueous drops

    NASA Astrophysics Data System (ADS)

    Aumann, E.; Tabazadeh, A.

    2008-12-01

    Previous studies suggest that saturated fatty acids or other lipids, which are known to be strong film-forming agents, form condensed films on aqueous drops. Specifically, stearic acid (SA) has been used in laboratory and modeling studies to mimic the surface composition of some particles in the atmosphere. In this study, laboratory measurements were used to determine the rate of SA spreading from a solid on aqueous surfaces,ranging in composition from ammonium sulfate to highly acidic sulfuric acid. Maximum spreading rates were measured on neutral electrolyte solutions, while spreading was not observed on aqueous sulfuric and hydrochloric acids (pH < 0). Also, the spreading rates on water and electrolyte surfaces declined sharply as the solution pH was lowered from 7 to 3. Spreading rates are reported with a dependence on the length of solid-aqueous-air boundary (triple interface perimeter). Spreading rates measured on bulk solutions were modeled on atmospheric particles to determine the time constant of organic film formation on aqueous drops. The time required for a saturated fatty acid to spread and coat a submicron salt particle or a cloud drop is on the order of seconds to minutes or minutes to hours, respectively. In conclusion, lipid coatings can form quickly on neutral or slightly acidic salt drops if a sufficient amount of lipid is present in the drop and the lipid is in direct contact with the aqueous solution surface. Rapid film formation and fast heterogeneous oxidation can provide an efficient way of converting water-insoluble organic films into more water-soluble components in aerosols or cloud drops.

  2. PRIMUS: Enhanced Specific Star Formation Rates in Close Galaxy Pairs

    NASA Astrophysics Data System (ADS)

    Wong, Kenneth C.; Blanton, Michael R.; Burles, Scott M.; Coil, Alison L.; Cool, Richard J.; Eisenstein, Daniel J.; Moustakas, John; Zhu, Guangtun; Arnouts, Stéphane

    2011-02-01

    Tidal interactions between galaxies can trigger star formation, which contributes to the global star formation rate (SFR) density of the universe and could be a factor in the transformation of blue, star-forming galaxies to red, quiescent galaxies over cosmic time. We investigate tidally triggered star formation in isolated close galaxy pairs drawn from the Prism Multi-Object Survey (PRIMUS), a low-dispersion prism redshift survey that has measured ~120,000 robust galaxy redshifts over 9.1 deg2 out to z ~ 1. We select a sample of galaxies in isolated galaxy pairs at redshifts 0.25 <= z <= 0.75, with no other objects within a projected separation of 300 h -1 kpc and Δz/(1 + z) = 0.01, and compare them to a control sample of isolated galaxies to test for systematic differences in their rest-frame FUV - r and NUV - r colors as a proxy for relative specific star formation rates (SSFRs). We find that galaxies in rp <= 50 h -1 kpc pairs have bluer dust-corrected UV - r colors on average than the control galaxies by -0.134 ± 0.045 mag in FUV - r and -0.075 ± 0.038 mag in NUV - r, corresponding to an ~15%-20% increase in SSFR. This indicates an enhancement in SSFR due to tidal interactions. We also find that this relative enhancement is greater for a subset of rp <= 30 h -1 kpc pair galaxies, for which the average color offsets are -0.193 ± 0.065 mag in FUV - r and -0.159 ± 0.048 mag in NUV - r, corresponding to an ~25%-30% increase in SSFR. We test for evolution in the enhancement of tidally triggered star formation with redshift across our sample redshift range and find marginal evidence for a decrease in SSFR enhancement from 0.25 <= z <= 0.5 to 0.5 <= z <= 0.75. This indicates that a change in enhanced star formation triggered by tidal interactions in low-density environments is not a contributor to the decline in the global SFR density across this redshift range.

  3. Star Formation Rate in Holmberg IX Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Andjelic, M. M.

    2011-12-01

    In this paper we use previously determined Hα fluxes for dwarf galaxy Holmberg IX (Arbutina et al. 2009) to calculate star formation rate (SFR) in this galaxy. We discuss possible contaminations of Hα flux and, for the first time, we take into account optical emission from supernova remnants (SNRs) as a possible source of contamination of Hα flux. Derived SFR for Holmberg IX is 3.4×10-4M_{⊙} yr-1. Our value is lower then in previous studies, due to luminous shock-heated source M&H 9-10, possible hypernova remnant, which we excluded from the total Hα flux in our calculation of SFR.

  4. REVEALING TYPE Ia SUPERNOVA PHYSICS WITH COSMIC RATES AND NUCLEAR GAMMA RAYS

    SciTech Connect

    Horiuchi, Shunsaku; Beacom, John F. E-mail: beacom@mps.ohio-state.ed

    2010-11-01

    Type Ia supernovae (SNe Ia) remain mysterious despite their central importance in cosmology and their rapidly increasing discovery rate. The progenitors of SNe Ia can be probed by the delay time between progenitor birth and explosion as SNe Ia. The explosions and progenitors of SNe Ia can be probed by MeV nuclear gamma rays emitted in the decays of radioactive nickel and cobalt into iron. We compare the cosmic star formation and SN Ia rates, finding that their different redshift evolution requires a large fraction of SNe Ia to have large delay times. A delay-time distribution of the form t {sup -}{alpha} with {alpha} = 1.0 {+-} 0.3 provides a good fit, implying that 50% of SNe Ia explode more than {approx}1 Gyr after progenitor birth. The extrapolation of the cosmic SN Ia rate to z = 0 agrees with the rate we deduce from catalogs of local SNe Ia. We investigate prospects for gamma-ray telescopes to exploit the facts that escaping gamma rays directly reveal the power source of SNe Ia and uniquely provide tomography of the expanding ejecta. We find large improvements relative to earlier studies by Gehrels et al. in 1987 and Timmes and Woosley in 1997 due to larger and more certain SN Ia rates and advances in gamma-ray detectors. The proposed Advanced Compton Telescope, with a narrow-line sensitivity {approx}60 times better than that of current satellites, would, on an annual basis, detect up to {approx}100 SNe Ia (3{sigma}) and provide revolutionary model discrimination for SNe Ia within 20 Mpc, with gamma-ray light curves measured with {approx}10{sigma} significance daily for {approx}100 days. Even more modest improvements in detector sensitivity would open a new and invaluable astronomy with frequent SN Ia gamma-ray detections.

  5. On the cosmic evolution of the specific star formation rate

    NASA Astrophysics Data System (ADS)

    Lehnert, M. D.; van Driel, W.; Le Tiran, L.; Di Matteo, P.; Haywood, M.

    2015-05-01

    The apparent correlation between the specific star formation rate (sSFR) and total stellar mass (M⋆) of galaxies is a fundamental relationship indicating how they formed their stellar populations. To attempt to understand this relation, we hypothesize that the relation and its evolution is regulated by the increase in the stellar and gas mass surface density in galaxies with redshift, which is itself governed by the angular momentum of the accreted gas, the amount of available gas, and by self-regulation of star formation. With our model, we can reproduce the specific SFR - M⋆ relations at z ~ 1-2 by assuming gas fractions and gas mass surface densities similar to those observed for z = 1-2 galaxies. We further argue that it is the increasing angular momentum with cosmic time that causes a decrease in the surface density of accreted gas. The gas mass surface densities in galaxies are controlled by the centrifugal support (i.e., angular momentum), and the sSFR is predicted to increase as, sSFR(z) = (1 + z)3/tH0, as observed (where tH0 is the Hubble time and no free parameters are necessary). In addition, the simple evolution for the star-formation intensity we propose is in agreement with observations of Milky Way-like galaxies selected through abundance matching. At z ≳ 2, we argue that star formation is self-regulated by high pressures generated by the intense star formation itself. The star formation intensity must be high enough to either balance the hydrostatic pressure (a rather extreme assumption) or to generate high turbulent pressure in the molecular medium which maintains galaxies near the line of instability (i.e. Toomre Q ~ 1). We provide simple prescriptions for understanding these self-regulation mechanisms based on solid relationships verified through extensive study. In all cases, the most important factor is the increase in stellar and gas mass surface density with redshift, which allows distant galaxies to maintain high levels of s

  6. 'Nose method' of calculating critical cooling rates for glass formation

    NASA Technical Reports Server (NTRS)

    Weinberg, Michael C.; Uhlmann, Donald R.; Zanotto, Edgar D.

    1989-01-01

    The use of the so-called 'nose method' for computing critical cooling rates for glass formation is examined and compared with other methods, presenting data for the glass-forming systems SiO2, GeO2, and P2O5. It is shown that, for homogeneous crystallization, the nose-method will give an overestimate of Rc, a conclusion which was drawn after assessing the enfluence of a range of values for the parameters which control crystal growth and nucleation. The paper also proposes an alternative simple procedure (termed the 'cutoff method') for computing critical cooling rates from T-T-T diagrams, which was shown in the SiO2 and GeO2 systems to be superior to the nose method.

  7. The star formation rate intensity distribution function—. Comparison of observations with hierarchical galaxy formation

    NASA Astrophysics Data System (ADS)

    Barkana, Rennan

    2002-09-01

    Recently, Lanzetta et al. [ApJ (2002) in press] have measured the distribution of star formation rate intensity in galaxies at various redshifts. This data set has a number of advantages relative to galaxy luminosity functions; the effect of surface-brightness dimming on the selection function is simpler to understand, and this data set also probes the size distribution of galactic disks. We predict this function using semi-analytic models of hierarchical galaxy formation in a ΛCDM cosmology. We show that the basic trends found in the data follow naturally from the redshift evolution of dark matter halos. The data are consistent with a constant efficiency of turning gas into stars in galaxies, with a best-fit value of 2%, where dust obscuration is neglected; equivalently, the data are consistent with a cosmic star formation rate which is constant to within a factor of two at all redshifts above two. However, the practical ability to use this kind of distribution to measure the total cosmic star formation rate is limited by the predicted shape of an approximate power law with a smoothly varying power, without a sharp break.

  8. Calibration of Star Formation Rates Across the Electromagnetic Spectrum

    NASA Technical Reports Server (NTRS)

    Cardiff, Ann H.

    2011-01-01

    Measuring and mapping star-forming activity in galaxies is a key element for our understanding of their broad- band spectra, and their structure and evolution in our local, as well as the high-redshift Universe. The main tool we use for these measurements is the observed luminosity in various spectral lines and/or continuum bands. However, the available star-formation rate (SFR) indicators are often discrepant and subject to physical biases and calibration uncertainties. We are organizing a special session at the 2012 IAU General Assembly in Beijing, China (August 20-31, 2012) in order to bring together theoreticians and observers working in different contexts of star-formation to discuss the status of current SFR indicators, to identify open issues and to define a strategic framework for their resolution. The is an ideal time to synthesize information from the current golden era of space astrophysics and still have influence on the upcoming missions that will broaden our view of star-formation. We will be including high-energy constraints on SFR in the program and encourage participation from the high energy astrophysics community.

  9. Collapsing molecular clouds and their evolving star formation rate

    NASA Astrophysics Data System (ADS)

    Vazquez-Semadeni, Enrique

    2015-08-01

    I will discuss the evidence suggesting that molecular clouds (MCs) may be in global, hierarchical gravitational collapse, and the regulation of their star formation rate (SFR) by stellar feedback. The evidence includes observations of multi-scale collapse in MCs, and numerical simulations of MC evolution, from their formation to the onset of gravitational collapse, then the onset of star formation, and, finally, the clouds' destruction by stellar feedback. In this scenario, the SFR evolves in time, increasing until the feedback begins to destroy the clouds, at which point it drops significantly, or stops altogether. This evolution of the SFR explains the observed form of the age histograms of embedded clusters, the evolutionary sequence observed for giant MCs in the Large Magellanic Cloud, and the locus of clouds in the SFR vs. mass diagram of Gao & Solomon. Finally, this scenario implies that the material that at one time conforms a low-mass star-forming MC such as Perseus, will constitute the massive-SF clumps embedded in a massive GMC, and that MCs constitute a regime of flow rather than well defined objects.

  10. THE CURRENT STAR FORMATION RATE OF K+A GALAXIES

    SciTech Connect

    Nielsen, Danielle M.; Ridgway, Susan E.; De Propris, Roberto; Goto, Tomotsugu

    2012-12-20

    We derive the stacked 1.4 GHz flux from the FIRST survey for 811 K+A galaxies selected from the Sloan Digital Sky Survey Data Release 7. For these objects we find a mean flux density of 56 {+-} 9 {mu}Jy. A similar stack of radio-quiet white dwarfs yields an upper limit of 43 {mu}Jy at a 5{sigma} significance to the flux in blank regions of the sky. This implies an average star formation rate of 1.6 {+-} 0.3 M{sub Sun} yr{sup -1} for K+A galaxies. However, the majority of the signal comes from {approx}4% of K+A fields that have aperture fluxes above the 5{sigma} noise level of the FIRST survey. A stack of the remaining galaxies shows little residual flux consistent with an upper limit on star formation of 1.3 M{sub Sun} yr{sup -1}. Even for a subset of 456 'young' (spectral ages <250 Myr) K+A galaxies, we find that the stacked 1.4 GHz flux is consistent with no current star formation. Our data suggest that the original starburst has been terminated in the majority of K+A galaxies, but that this may represent part of a duty cycle where a fraction of these galaxies may be active at a given moment with dusty starbursts and active galactic nuclei being present.

  11. SHAPING THE DUST MASS-STAR-FORMATION RATE RELATION

    SciTech Connect

    Hjorth, Jens; Gall, Christa; Michałowski, Michał J. E-mail: cgall@phys.au.dk

    2014-02-20

    There is a remarkably tight relation between the observationally inferred dust masses and star-formation rates (SFRs) of Sloan Digital Sky Survey galaxies, M {sub dust} ∝ SFR{sup 1.11}. Here we extend the M {sub dust}-SFR relation to the high end and show that it bends over at very large SFRs (i.e., dust masses are lower than predicted for a given SFR). We identify several distinct evolutionary processes in the diagram: (1) a star-bursting phase in which dust builds up rapidly at early times. The maximum attainable dust mass in this process is the cause of the bend-over of the relation. A high dust-formation efficiency, a bottom-light initial mass function, and negligible supernova shock dust destruction are required to produce sufficiently high dust masses. (2) A quiescent star-forming phase in which the subsequent parallel decline in dust mass and SFR gives rise to the M {sub dust}-SFR relation, through astration and dust destruction. The dust-to-gas ratio is approximately constant along the relation. We show that the power-law slope of the M {sub dust}-SFR relation is inversely proportional to the global Schmidt-Kennicutt law exponent (i.e., ∼0.9) in simple chemical evolution models. (3) A quenching phase which causes star formation to drop while the dust mass stays roughly constant or drops proportionally. Combined with merging, these processes, as well as the range in total baryonic mass, give rise to a complex population of the diagram which adds significant scatter to the original M {sub dust}-SFR relation. (4) At very high redshifts, a population of galaxies located significantly below the local relation is predicted.

  12. The formation of cluster elliptical galaxies as revealed by extensive star formation.

    PubMed

    Stevens, J A; Ivison, R J; Dunlop, J S; Smail, Ian R; Percival, W J; Hughes, D H; Röttgering, H J A; Van Breugel, W J M; Reuland, M

    2003-09-18

    The most massive galaxies in the present-day Universe are found to lie in the centres of rich clusters. They have old, coeval stellar populations suggesting that the bulk of their stars must have formed at early epochs in spectacular starbursts, which should be luminous phenomena when observed at submillimetre wavelengths. The most popular model of galaxy formation predicts that these galaxies form in proto-clusters at high-density peaks in the early Universe. Such peaks are indicated by massive high-redshift radio galaxies. Here we report deep submillimetre mapping of seven high-redshift radio galaxies and their environments. These data confirm not only the presence of spatially extended regions of massive star-formation activity in the radio galaxies themselves, but also in companion objects previously undetected at any wavelength. The prevalence, orientation, and inferred masses of these submillimetre companion galaxies suggest that we are witnessing the synchronous formation of the most luminous elliptical galaxies found today at the centres of rich clusters of galaxies. PMID:13679908

  13. The UV + IR Hybrid Star Formation Rate Across NGC6946

    NASA Astrophysics Data System (ADS)

    Eufrasio, Rafael T.; Lehmer, Bret; Dwek, Eli; Arendt, Richard G.

    2016-01-01

    Knowledge of the star formation rate (SFR) of galaxies is essential to understand galaxy evolution and thus determining reliable, simple tracers of star-forming activity is of paramount importance to astrophysics. For instance, intrinsic ultraviolet (UV) emission from young stars is an excellent tracer of the SFR. Observed UV luminosities, however, have been strongly attenuated by intervening interstellar dust. Since emission from hot dust is readily available from IRAS, Spitzer, and WISE, it is common practice to combine mid-IR emission (around 25 μm) with observed UV in order to obtain an SFR diagnostic of the form Lobs(FUV) + acorr × Lobs(25 μm). Conventionally, a single correction acorr, previously determined for a sample of galaxies, is used. Here we test the reliability of this hybrid SFR diagnostic, allowing for a variable correction factor acorr. For this, we have performed broadband UV-to-IR SED fittings in order to model the star formation histories across the spiral galaxy NGC6946. We have obtained SFRs and stellar masses across the galaxy, from physical scales of 5 kpc down to 500 pc. We find that acorr varies significantly across the galaxy and increases with increasing specific star formation rate (sSFR), the ratio of SFR and stellar mass (or the ratio of young and old stars). The correction acorr does not seem to be correlated to the amount of attenuation AV. Variation of acorr is most likely caused by different mixes of young and old stellar populations across the galaxy. This finding agrees well with our previous results for the interacting spiral galaxy NGC 6872, for which we have demonstrated the variation of acorr and a its correlation with sSFR. Our results show the need of caution when using only two broadband filters in order to determine SFR of individual galaxies or sub-galactic regions. The dust emission most likely overestimates SFR for highly star-forming, high sSFR regions, and underestimates it for more quiescent, low sSFR regions.

  14. QM/MM studies reveal pathways leading to the quenching of the formation of thymine dimer photoproduct by flanking bases.

    PubMed

    Lee, Wook; Matsika, Spiridoula

    2015-04-21

    It is known that the formation of the photochemical product of thymine-thymine cyclobutane pyrimidine dimer (TT-CPD) formed upon UV excitation in DNA is significantly affected by the nature of the flanking bases, and that the oxidation potential of the flanking base correlates with the quenching of TT-CPD formation. However, the electronic details of this correlation have remained controversial. The quenching of thymine dimer formation exerted by flanking bases was suggested to be driven by both conformational and electronic effects. In the present study, we examine both of these effects using umbrella sampling and a quantum mechanical/molecular mechanical (QM/MM) approach for selected model systems. Our results demonstrate that a charge transfer (CT) state between the flanking base and the adjacent thymine base can provide a decay pathway for the population to escape from dimer formation, which eventually leads to the formation of an exciplex. The QM/MM vertical excitation energies also reveal that the oxidation potential of flanking bases correlates with the energy level of the CT state, thereby determining whether the CT state intersects with the state that can lead to dimer formation. The consistency between these results and experimentally obtained dimer formation rates implies that the quenching of dimer formation is mainly attributed to the decay pathway via the CT state. The present results further underline the importance of the electronic effects in quenching. PMID:25776223

  15. The star formation rates of active galactic nuclei host galaxies

    NASA Astrophysics Data System (ADS)

    Ellison, Sara L.; Teimoorinia, Hossen; Rosario, David J.; Mendel, J. Trevor

    2016-05-01

    Using artificial neural network predictions of total infrared luminosities (LIR), we compare the host galaxy star formation rates (SFRs) of ˜21 000 optically selected active galactic nuclei (AGN), 466 low-excitation radio galaxies (LERGs) and 721 mid-IR-selected AGN. SFR offsets (ΔSFR) relative to a sample of star-forming `main-sequence' galaxies (matched in M⋆, z and local environment) are computed for the AGN hosts. Optically selected AGN exhibit a wide range of ΔSFR, with a distribution skewed to low SFRs and a median ΔSFR = -0.06 dex. The LERGs have SFRs that are shifted to even lower values with a median ΔSFR = -0.5 dex. In contrast, mid-IR-selected AGN have, on average, SFRs enhanced by a factor of ˜1.5. We interpret the different distributions of ΔSFR amongst the different AGN classes in the context of the relative contribution of triggering by galaxy mergers. Whereas the LERGs are predominantly fuelled through low accretion rate secular processes which are not accompanied by enhancements in SFR, mergers, which can simultaneously boost SFRs, most frequently lead to powerful, obscured AGN.

  16. Regolith Formation Rates and Evolution from the Diviner Lunar Radiometer

    NASA Astrophysics Data System (ADS)

    Hayne, P. O.; Ghent, R. R.; Bandfield, J. L.; Vasavada, A. R.; Williams, J. P.; Siegler, M. A.; Lucey, P. G.; Greenhagen, B. T.; Elder, C. M.; Paige, D. A.

    2015-12-01

    Fragmentation and overturn of lunar surface materials produces a layer of regolith, which increases in thickness through time. Experiments on the lunar surface during the Apollo era, combined with remote sensing, found that the upper 10's of cm of regolith exhibit a rapid increase in density and thermal conductivity with depth. This is interpreted to be the signature of impact gardening, which operates most rapidly in the uppermost layers. Gravity data from the GRAIL mission showed that impacts have also extensively fractured the deeper crust. The breakdown and mixing of crustal materials is therefore a central process to lunar evolution and must be understood in order to interpret compositional information from remote sensing and sample analysis. Recently, thermal infrared data from the Lunar Reconnaissance Orbiter (LRO) Diviner radiometer were used to provide the first remote observational constraints on the rate of ejecta breakdown around craters < 1 Ga (Ghent et al., 2014). Here, we use nighttime regolith temperatures derived from Diviner data to constrain regolith thermal inertia, thickness, and spatial variability. Applied to models, these new data help improve understanding of regolith formation on a variety of geologic units. We will also discuss several anomalous features that merit further investigation. Reference: Ghent, R. R., Hayne, P. O., Bandfield, J. L., Campbell, B. A., Allen, C. C., Carter, L. M., & Paige, D. A. (2014). Constraints on the recent rate of lunar ejecta breakdown and implications for crater ages. Geology, 42(12), 1059-1062.

  17. Calibrating UV Star Formation Rates for Dwarf Galaxies from STARBIRDS

    NASA Astrophysics Data System (ADS)

    McQuinn, Kristen B. W.; Skillman, Evan D.; Dolphin, Andrew E.; Mitchell, Noah P.

    2015-08-01

    Integrating our knowledge of star formation (SF) traced by observations at different wavelengths is essential for correctly interpreting and comparing SF activity in a variety of systems and environments. This study compares extinction corrected integrated ultraviolet (UV) emission from resolved galaxies with color-magnitude diagram (CMD) based star formation rates (SFRs) derived from resolved stellar populations and CMD fitting techniques in 19 nearby starburst and post-starburst dwarf galaxies. The data sets are from the panchromatic Starburst Irregular Dwarf Survey and include deep legacy GALEX UV imaging, Hubble Space Telescope optical imaging, and Spitzer MIPS imaging. For the majority of the sample, the integrated near-UV fluxes predicted from the CMD-based SFRs—using four different models—agree with the measured, extinction corrected, integrated near-UV fluxes from GALEX images, but the far-UV (FUV) predicted fluxes do not. Furthermore, we find a systematic deviation between the SFRs based on integrated FUV luminosities and existing scaling relations, and the SFRs based on the resolved stellar populations. This offset is not driven by different SF timescales, variations in SFRs, UV attenuation, nor stochastic effects. This first comparison between CMD-based SFRs and an integrated FUV emission SFR indicator suggests that the most likely cause of the discrepancy is the theoretical FUV-SFR calibration from stellar evolutionary libraries and/or stellar atmospheric models. We present an empirical calibration of the FUV-based SFR relation for dwarf galaxies, with uncertainties, which is ˜53% larger than previous relations. Based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA), and the Canadian Astronomy Data Centre (CADC/NRC/CSA).

  18. Comparing infrared star formation rate indicators with optically derived quantities

    NASA Astrophysics Data System (ADS)

    Young, J. E.; Gronwall, C.; Salzer, J. J.; Rosenberg, J. L.

    2014-09-01

    We examine the UV reprocessing efficiencies of warm dust and polycyclic aromatic hydrocarbons (PAHs) through an analysis of the mid- and far-infrared surface luminosity densities of 85 nearby Hα-selected star-forming galaxies detected by the volume-limited KPNO (Kitt Peak National Observatory) International Spectroscopic Survey (KISS). Because Hα selection is not biased towards continuum-bright objects, the KISS sample spans a wide range in stellar masses (108-1012 M⊙), as well as Hα luminosity (1039-1043 erg s-1), mid-infrared 8.0 μm luminosity (1041-1044 erg s-1), and [Bw - R] colour (-0.1-2.2). We find that mid-infrared PAH emission in the Spitzer InfraRed Array Camera (IRAC) 8.0 μm band correlates with star formation, and that the efficiency with which galaxies reprocess UV energy into PAH emission depends on metallicity. We also find that the relationship between far-infrared luminosity in the Spitzer Multiband Imaging Photometer for Spitzer 24 μm band pass and Hα-measured star formation rate varies from galaxy to galaxy within our sample; we do not observe a metallicity dependence in this relationship. We use optical colours and established mass-to-light relationships to determine stellar masses for the KISS galaxies; we compare these masses to those of nearby galaxies as a confirmation that the volume-limited nature of KISS avoids strong biases. We also examine the relationship between IRAC 3.6 μm luminosity and galaxy stellar mass, and find a colour-dependent correlation between the two.

  19. Kinetics of silicide formation over a wide range of heating rates spanning six orders of magnitude

    SciTech Connect

    Molina-Ruiz, Manel; Lopeandía, Aitor F.; Gonzalez-Silveira, Marta; Garcia, Gemma; Clavaguera-Mora, Maria T.; Peral, Inma; Rodríguez-Viejo, Javier

    2014-07-07

    Kinetic processes involving intermediate phase formation are often assumed to follow an Arrhenius temperature dependence. This behavior is usually inferred from limited data over narrow temperature intervals, where the exponential dependence is generally fully satisfied. However, direct evidence over wide temperature intervals is experimentally challenging and data are scarce. Here, we report a study of silicide formation between a 12 nm film of palladium and 15 nm of amorphous silicon in a wide range of heating rates, spanning six orders of magnitude, from 0.1 to 10{sup 5 }K/s, or equivalently more than 300 K of variation in reaction temperature. The calorimetric traces exhibit several distinct exothermic events related to interdiffusion, nucleation of Pd{sub 2}Si, crystallization of amorphous silicon, and vertical growth of Pd{sub 2}Si. Interestingly, the thickness of the initial nucleation layer depends on the heating rate revealing enhanced mass diffusion at the fastest heating rates during the initial stages of the reaction. In spite of this, the formation of the silicide strictly follows an Arrhenius temperature dependence over the whole temperature interval explored. A kinetic model is used to fit the calorimetric data over the complete heating rate range. Calorimetry is complemented by structural analysis through transmission electron microscopy and both standard and in-situ synchrotron X-ray diffraction.

  20. Acute effects of Solanum malacoxylon on bone formation rates in growing rats.

    PubMed

    Norrdin, R W; de Barros, C S; Queille, M L; Carré, M; Miravet, L

    1979-11-01

    The plant Solanum malacoxylon is responsible for a syndrome of hypercalcemia, soft tissue mineralization, and progressive wasting in South American cattle known as enteque seco or espichamento. There is evidence that a glycoside of 1,25-dihydroxycholecalciferol is the active principle in the plant. The basis for the hyperostosis seen in the disease is unclear. To study the acute effects on bone formation rates, 8-week-old rats were given an aqueous extract equivalent to 250 or 1000 mg of Solanum daily per os for 7 days. Bones were labeled by injection of fluochrome 2 days before the start of treatment and 2 days prior to sacrifice. Morphometric evaluation of undecalcified sections of caudal vertebrae revealed an increased amount of trabecular bone in both Solanum treated groups with no difference due to dose level. This was associated with an increase in the bone apposition rate on trabecular surfaces. No differences were found in the amount of osteoid seam width. Periosteal apposition rate and endochondral bone formation were also measured and no significant differences found. The findings indicate that acute stimulation of cell level bone formation on trabecular surfaces may play a role in the hyperostosis seen in the naturally occurring condition. PMID:116737

  1. The Range of the Star Formation Rate in Local BCDs

    NASA Astrophysics Data System (ADS)

    Hopp, U.

    We will compare the star formation rate (SFR) obtained for the emission line galaxy sample (ELGS) of Popescu et al (1999, 2000) and of very nearby Blue Compact Dwarf Galaxies (BCD) which were resolved into individual stars with HST. For the ELGS, the SFR was derived from the Balmer line flux applying standard calibration. The new metal-depend calibrations of Weilbacher & Fritze-von Alvensleben (2001) will be considered. The galaxies of the ELGS are distributed in intermediate to very low environment galaxy densities. About half a dozen nearby (D <= 7 Mpc) BCDs in similar density regimes have been resolved into individual stars using either WFPC2 or NIC2 aboard HST. Analysing their color-magnitude diagrams yield clues on the recent and past SFR (e. g. Schulte-Ladbeck et al., 2001, Hopp, 2001). From both samples, we found that the SFR of BCDs is, on average, surprisingly low. For the ELGS, the values range from 2.2 Msolar yr-1 down to 0.01 Msolar yr-1, with two third of them below 0.3 Msolar yr-1. BCDs with high, star-burst like SFR (>= 0.8 Msolar yr-1) are rare (<= 10%). References: Hopp, U., 2001, in: K. de Boer, Proc. of ``Dwarf Galaxies and their Environment'', January 2001, Shacker Verlag, in press Popescu, C.C., Hopp, U., 2000, A&AS, 142, 247 Popescu, C.C., Hopp, U., Rosa, M., 1999, A&A, 350, 414 Schulte-Ladbeck, R.E., Hopp, U., Greggio, L., Crone, M., Drozdovsky, I.O., 2001, AJ (June), in press Weilbacher, P.M., Fritze-von Alvensleben, U., 2001, A&A, in press (astro-ph/0105282)

  2. Decreased specific star formation rates in AGN host galaxies

    NASA Astrophysics Data System (ADS)

    Shimizu, T. Taro; Mushotzky, Richard F.; Meléndez, Marcio; Koss, Michael; Rosario, David J.

    2015-09-01

    We investigate the location of an ultra-hard X-ray selected sample of active galactic nuclei (AGN) from the Swift Burst Alert Telescope (BAT) catalogue with respect to the main sequence (MS) of star-forming galaxies using Herschel-based measurements of the star formation rate (SFR) and M*'s from Sloan Digital Sky Survey photometry where the AGN contribution has been carefully removed. We construct the MS with galaxies from the Herschel Reference Survey and Herschel Stripe 82 Survey using the exact same methods to measure the SFR and M* as the Swift/BAT AGN. We find that a large fraction of the Swift/BAT AGN lie below the MS indicating decreased specific SFR (sSFR) compared to non-AGN galaxies. The Swift/BAT AGN are then compared to a high-mass galaxy sample (CO Legacy Database for GALEX Arecibo SDSS Survey, COLD GASS), where we find a similarity between the AGN in COLD GASS and the Swift/BAT AGN. Both samples of AGN lie firmly between star-forming galaxies on the MS and quiescent galaxies far below the MS. However, we find no relationship between the X-ray luminosity and distance from the MS. While the morphological distribution of the BAT AGN is more similar to star-forming galaxies, the sSFR of each morphology is more similar to the COLD GASS AGN. The merger fraction in the BAT AGN is much higher than the COLD GASS AGN and star-forming galaxies and is related to distance from the MS. These results support a model in which bright AGN tend to be in high-mass star-forming galaxies in the process of quenching which eventually starves the supermassive black hole itself.

  3. ON STAR FORMATION RATES AND STAR FORMATION HISTORIES OF GALAXIES OUT TO z {approx} 3

    SciTech Connect

    Wuyts, Stijn; Foerster Schreiber, Natascha M.; Lutz, Dieter; Nordon, Raanan; Berta, Stefano; Genzel, Reinhard; Magnelli, Benjamin; Poglitsch, Albrecht; Altieri, Bruno; Andreani, Paola; Aussel, Herve; Daddi, Emanuele; Elbaz, David; Cimatti, Andrea; Koekemoer, Anton M.; Maiolino, Roberto; McGrath, Elizabeth J.

    2011-09-01

    We compare multi-wavelength star formation rate (SFR) indicators out to z {approx} 3 in the GOODS-South field. Our analysis uniquely combines U to 8 {mu}m photometry from FIREWORKS, MIPS 24 {mu}m and PACS 70, 100, and 160 {mu}m photometry from the PEP, and H{alpha} spectroscopy from the SINS survey. We describe a set of conversions that lead to a continuity across SFR indicators. A luminosity-independent conversion from 24 {mu}m to total infrared luminosity yields estimates of L{sub IR} that are in the median consistent with the L{sub IR} derived from PACS photometry, albeit with significant scatter. Dust correction methods perform well at low-to-intermediate levels of star formation. They fail to recover the total amount of star formation in systems with large SFR{sub IR}/SFR{sub UV} ratios, typically occuring at the highest SFRs (SFR{sub UV+IR} {approx}> 100 M{sub sun} yr{sup -1}) and redshifts (z {approx}> 2.5) probed. Finally, we confirm that H{alpha}-based SFRs at 1.5 < z < 2.6 are consistent with SFR{sub SED} and SFR{sub UV+IR} provided extra attenuation toward H II regions is taken into account (A{sub V,neb} = A{sub V,continuum}/0.44). With the cross-calibrated SFR indicators in hand, we perform a consistency check on the star formation histories inferred from spectral energy distribution (SED) modeling. We compare the observed SFR-M relations and mass functions at a range of redshifts to equivalents that are computed by evolving lower redshift galaxies backward in time. We find evidence for underestimated stellar ages when no stringent constraints on formation epoch are applied in SED modeling. We demonstrate how resolved SED modeling, or alternatively deep UV data, may help to overcome this bias. The age bias is most severe for galaxies with young stellar populations and reduces toward older systems. Finally, our analysis suggests that SFHs typically vary on timescales that are long (at least several 100 Myr) compared to the galaxies' dynamical time.

  4. A cluster in the making: ALMA reveals the initial conditions for high-mass cluster formation

    NASA Astrophysics Data System (ADS)

    Rathborne, Jill

    2015-08-01

    Despite their importance, very little is known about the formation of star clusters. An understanding of their formation requires observations of their natal dust and gas well before the onset of star formation. In recent Galactic Plane surveys, one object, G0.253+0.016, stands out as extreme. Identified as a cold, dense, massive molecular clump devoid of prevalent star-formation, it has exactly the properties expected for a clump that may form an Arches-like cluster. Located at a distance of ~8.5 kpc, G0.253+0.016 lies ~100 pc from the Galactic Centre, in the Central Molecular Zone (CMZ).In this talk I will showcase our recent ALMA data of the 90 GHz continuum and line emission toward G0.253+0.016. The data are spectacular reveal a complex network of structures: there is emission on all spatial scales, the morphology of which ranges from small, compact regions to extended, filamentary structures that are seen in both emission and absorption. A statistical analysis of the structure within G0.253+0.016 demonstrates the dominance of turbulence. The talk will summarise our recent results and the emerging picture of cluster formation in the extreme, high-pressure environment of the CMZ that is revealed by the new ALMA data.

  5. Reliability and Validity of Teacher Rating Procedures in the Assessment of Hyperactivity as a Function of Rating Scale Format.

    ERIC Educational Resources Information Center

    Sandoval, Jonathan; Lambert, Nadine M.

    The effects of varying the formats of behavior rating scale items on teacher ratings of student hyperactivity were investigated. Two hundred forty-two teachers were asked to rate a variety of children; some had been identified as hyperactive by physicians, parents, or teachers; some were not considered hyperactive; and others were randomly…

  6. STAR FORMATION IN THE BULLET CLUSTER. I. THE INFRARED LUMINOSITY FUNCTION AND STAR FORMATION RATE ,

    SciTech Connect

    Sun Mi Chung; Gonzalez, Anthony H.; Clowe, Douglas; Markevitch, Maxim; Zaritsky, Dennis

    2010-12-20

    The Bullet Cluster is a massive galaxy cluster at z = 0.297 undergoing a major supersonic (Mach 3) merger event. Using data from Spitzer MIPS and the Infrared Array Camera, optical imaging, and optical spectroscopy, we present the global star formation rate (SFR) of this unique cluster. Using a 90% spectroscopically complete sample of 37 star-forming MIPS confirmed cluster members out to R < 1.7 Mpc, and the Rieke et al. relation to convert from 24 {mu}m flux to SFR, we calculate an integrated obscured SFR of 267 M{sub sun} yr{sup -1} and a specific SFR of 28 M{sub sun} yr{sup -1} per 10{sup 14} M{sub sun}. The cluster mass normalized integrated SFR of the Bullet Cluster is among the highest in a sample of eight other clusters and cluster mergers from the literature. Five LIRGs and one ULIRG contribute 30% and 40% of the total SFR of the cluster, respectively. To investigate the origin of the elevated specific SFR, we compare the infrared luminosity function (IR LF) of the Bullet Cluster to those of Coma (evolved to z = 0.297) and CL1358+62. The Bullet Cluster IR LF exhibits an excess of sources compared to the IR LFs of the other massive clusters. A Schechter function fit of the Bullet Cluster IR LF yields L* = 44.68 {+-} 0.11 erg s{sup -1}, which is {approx}0.25 and 0.35 dex brighter than L* of evolved Coma and CL1358+62, respectively. The elevated IR LF of the Bullet Cluster relative to other clusters can be explained if we attribute the 'excess' star-forming IR galaxies to a population associated with the infalling group that has not yet been transformed into quiescent galaxies. In this case, the timescale required for quenching star formation in the cluster environment must be longer than the timescale since the group's accretion-a few hundred million years. We suggest that 'strangulation' is likely to be an important process in the evolution of star formation in clusters.

  7. Effects of stellar rotation on star formation rates and comparison to core-collapse supernova rates

    SciTech Connect

    Horiuchi, Shunsaku; Beacom, John F.; Bothwell, Matt S.; Thompson, Todd A.

    2013-06-01

    We investigate star formation rate (SFR) calibrations in light of recent developments in the modeling of stellar rotation. Using new published non-rotating and rotating stellar tracks, we study the integrated properties of synthetic stellar populations and find that the UV to SFR calibration for the rotating stellar population is 30% smaller than for the non-rotating stellar population, and 40% smaller for the Hα to SFR calibration. These reductions translate to smaller SFR estimates made from observed UV and Hα luminosities. Using the UV and Hα fluxes of a sample of ∼300 local galaxies, we derive a total (i.e., sky-coverage corrected) SFR within 11 Mpc of 120-170 M {sub ☉} yr{sup –1} and 80-130 M {sub ☉} yr{sup –1} for the non-rotating and rotating estimators, respectively. Independently, the number of core-collapse supernovae discovered in the same volume requires a total SFR of 270{sub −80}{sup +110} M{sub ⊙} yr{sup −1}, suggesting a tension with the SFR estimates made with rotating calibrations. More generally, when compared with the directly estimated SFR, the local supernova discoveries strongly constrain any physical effects that might increase the energy output of massive stars, including, but not limited to, stellar rotation. The cosmic SFR and cosmic supernova rate data, on the other hand, show the opposite trend, with the cosmic SFR higher than that inferred from cosmic supernovae, constraining a significant decrease in the energy output of massive stars. Together, these lines of evidence suggest that the true SFR calibration factors cannot be too far from their canonical values.

  8. Simultaneous Measurement of Amyloid Fibril Formation by Dynamic Light Scattering and Fluorescence Reveals Complex Aggregation Kinetics

    PubMed Central

    Streets, Aaron M.; Sourigues, Yannick; Kopito, Ron R.; Melki, Ronald; Quake, Stephen R.

    2013-01-01

    An apparatus that combines dynamic light scattering and Thioflavin T fluorescence detection is used to simultaneously probe fibril formation in polyglutamine peptides, the aggregating subunit associated with Huntington's disease, in vitro. Huntington's disease is a neurodegenerative disorder in a class of human pathologies that includes Alzheimer's and Parkinson's disease. These pathologies are all related by the propensity of their associated protein or polypeptide to form insoluble, β-sheet rich, amyloid fibrils. Despite the wide range of amino acid sequence in the aggregation prone polypeptides associated with these diseases, the resulting amyloids display strikingly similar physical structure, an observation which suggests a physical basis for amyloid fibril formation. Thioflavin T fluorescence reports β-sheet fibril content while dynamic light scattering measures particle size distributions. The combined techniques allow elucidation of complex aggregation kinetics and are used to reveal multiple stages of amyloid fibril formation. PMID:23349924

  9. 41 CFR 109-40.306-1 - Recommended rate tender format.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 41 Public Contracts and Property Management 3 2012-01-01 2012-01-01 false Recommended rate tender format. 109-40.306-1 Section 109-40.306-1 Public Contracts and Property Management Federal Property...-1 Recommended rate tender format. Only those rate tenders which have been submitted by the...

  10. 41 CFR 109-40.306-1 - Recommended rate tender format.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false Recommended rate tender format. 109-40.306-1 Section 109-40.306-1 Public Contracts and Property Management Federal Property...-1 Recommended rate tender format. Only those rate tenders which have been submitted by the...

  11. 41 CFR 109-40.306-1 - Recommended rate tender format.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 41 Public Contracts and Property Management 3 2014-01-01 2014-01-01 false Recommended rate tender format. 109-40.306-1 Section 109-40.306-1 Public Contracts and Property Management Federal Property...-1 Recommended rate tender format. Only those rate tenders which have been submitted by the...

  12. 41 CFR 109-40.306-1 - Recommended rate tender format.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 41 Public Contracts and Property Management 3 2013-07-01 2013-07-01 false Recommended rate tender format. 109-40.306-1 Section 109-40.306-1 Public Contracts and Property Management Federal Property...-1 Recommended rate tender format. Only those rate tenders which have been submitted by the...

  13. 41 CFR 109-40.306-1 - Recommended rate tender format.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Recommended rate tender format. 109-40.306-1 Section 109-40.306-1 Public Contracts and Property Management Federal Property...-1 Recommended rate tender format. Only those rate tenders which have been submitted by the...

  14. Comparison of Traditional and Alternative Fitness Teaching Formats on Heart Rate Intensity and Perceived Enjoyment.

    ERIC Educational Resources Information Center

    Ha, Amy Sau-ching; Heung-Sang Wong, Stephen

    2002-01-01

    Compared a traditional and an alternative (skill-fitness- music) fitness teaching format to determine whether there would be differences on Hong Kong middle school students' heart rate intensity and perceived enjoyment. Data from heart rate monitors and student surveys indicated that the two formats did not produce differences in heart rates.…

  15. Budget allocation and the revealed social rate of time preference for health.

    PubMed

    Paulden, Mike; Claxton, Karl

    2012-05-01

    Appropriate decisions based on cost-effectiveness evaluations of health-care technologies depend upon the cost-effectiveness threshold and its rate of growth as well as some social rate of time preference for health. A more traditional approach to this problem is outlined before a social decision-making approach is developed, which demonstrates that social time preference for health is revealed through the budget allocations made by a socially legitimate higher authority. The relationship between the social time preference rate for health, the growth rate of the cost-effectiveness threshold and the rate at which the higher authority can borrow or invest is then examined. We establish that the social time preference rate for health is implied by the budget allocation and the health production functions in each period. As such, the social time preference rate for health depends not on the social time preference rate for consumption or growth in the consumption value of health but on growth in the cost-effectiveness threshold and the rate at which the higher authority can save or borrow between periods. The implications for discounting and the policies of bodies such as NICE are then discussed. PMID:21438069

  16. Large fluctuations in the disassembly rate of microtubules revealed by atomic force microscopy.

    PubMed

    Thomson, Neil H; Kasas, Sandor; Riederer, Beat M; Catsicas, Stefan; Dietler, Giovanni; Kulik, Andrzej J; Forró, László

    2003-01-01

    Atomic force microscopy (AFM) in situ has been used to observe the cold disassembly dynamics of microtubules at a previously unrealised spatial resolution. Microtubules either electrostatically or covalently bound to aminosilane surfaces disassembled at room temperature under buffer solutions with no free tubulin present. This process was followed by taking sequential tapping-mode AFM images and measuring the change in the microtubule end position as a function of time, with an spatial accuracy down to +/-20nm and a temporal accuracy of +/-1s. As well as giving average disassembly rates on the order of 1-10 tubulin monomers per second, large fluctuations in the disassembly rate were revealed, indicating that the process is far from smooth and linear under these experimental conditions. The surface bound rates measured here are comparable to the rates for GMPCPP-tubulin microtubules free in solution, suggesting that inhibition of tubulin curvature through steric hindrance controls the average, relatively low disassembly rate. The large fluctuations in this rate are thought to be due to multiple pathways in the kinetics of disassembly with differing rate constants and/or stalling due to defects in the microtubule lattice. Microtubules that were covalently bound to the surface left behind the protofilaments covalently cross-linked to the aminosilane via glutaraldehyde during the disassembly process. Further work is needed to quantitatively assess the effects of surface binding on protofibril disassembly rates, reveal any differences in disassembly rates between the plus and minus ends and to enable assembly as well as disassembly to be imaged in the microscope fluid cell in real-time. PMID:12801676

  17. Attribution of halo merger mass ratio and star formation rate density

    NASA Astrophysics Data System (ADS)

    Kim, Sungeun; Jo, Jeong-woon; Hwang, Jihe; Youn, Soyoung; Park, Boha

    2016-06-01

    We have used codes for implementing the merger tree algorithm by Cole et al. (2007) and Parkinson et al. (2008) and derived the halo merger mass ratio of protocluster of galaxies across the cosmic time. The authors compare the observed and simulated star formation rates reported by the various groups and derive the star formation rate densities at different red-shifts. This study implies that an investigation of different mass variables should be incorporated into the analysis in order to accurately estimate cumulative star formation rates of galaxies and star formation rate densities as a function of red-shifts.

  18. High Rate of Microbleed Formation Following Primary Intracerebral Hemorrhage

    PubMed Central

    Mackey, Jason; Wing, Jeffrey J.; Norato, Gina; Sobotka, Ian; Menon, Ravi S.; Burgess, Richard E.; Gibbons, M. Chris; Shara, Nawar M.; Fernandez, Stephen; Jayam-Trouth, Annapurni; Russell, Laura; Edwards, Dorothy F.; Kidwell, Chelsea S.

    2016-01-01

    Introduction We sought to investigate the frequency of microbleed (MB) development following intracerebral hemorrhage (ICH) in a predominantly African-American population and to identify predictors of new MB formation. Methods The DECIPHER study was a prospective, longitudinal, MR-based cohort study designed to evaluate racial/ethnic differences in risk factors for MBs and to evaluate the prognostic impact of MBs in this ICH population. We evaluated new MB formation in 2 time periods: from baseline to 30 days and from 30 days to year 1. Results Of 200 subjects enrolled in DECIPHER, 84 had MRIs at all required timepoints to meet criteria for this analysis. In the baseline to day 30 analysis, 11 (13.1%) had new MBs, compared to 25 (29.8%) in the day 30 to year 1 analysis. Logistic regression analysis demonstrated that baseline number of MBs (OR 1.05 [95% CI 1.01, 1.08], p=0.01) was associated with new MB formation at 30 days. A logistic regression model predicting new MB at 1 year included baseline number of MBs (OR 1.05 [1.00, 1.11], p=0.046), baseline age (OR 1.05 [1.00, 1.10], p=0.04) and WMD disease score (OR 1.18 [0.96, 1.45]. p=0.115). Overall 28 of 84 (33.3%) ICH subjects formed new MBs at some point in the first year post-ICH. Conclusions We found that one-third of ICH subjects in this cohort surviving one year developed new MBs, which suggests a dynamic and rapidly progressive vasculopathy. Future studies are needed to examine the impact of new MB formation on patient outcomes. PMID:26311530

  19. Combined techniques for characterising pasta structure reveals how the gluten network slows enzymic digestion rate.

    PubMed

    Zou, Wei; Sissons, Mike; Gidley, Michael J; Gilbert, Robert G; Warren, Frederick J

    2015-12-01

    The aim of the present study is to characterise the influence of gluten structure on the kinetics of starch hydrolysis in pasta. Spaghetti and powdered pasta were prepared from three different cultivars of durum semolina, and starch was also purified from each cultivar. Digestion kinetic parameters were obtained through logarithm-of-slope analysis, allowing identification of sequential digestion steps. Purified starch and semolina were digested following a single first-order rate constant, while pasta and powdered pasta followed two sequential first-order rate constants. Rate coefficients were altered by pepsin hydrolysis. Confocal microscopy revealed that, following cooking, starch granules were completely swollen for starch, semolina and pasta powder samples. In pasta, they were completely swollen in the external regions, partially swollen in the intermediate region and almost intact in the pasta strand centre. Gluten entrapment accounts for sequential kinetic steps in starch digestion of pasta; the compact microstructure of pasta also reduces digestion rates. PMID:26041231

  20. Ultraviolet Morphology and Unobscured UV Star Formation Rates of CLASH Brightest Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Donahue, Megan; Connor, Thomas; Fogarty, Kevin; Li, Yuan; Voit, G. Mark; Postman, Marc; Koekemoer, Anton; Moustakas, John; Bradley, Larry; Ford, Holland

    2015-06-01

    Brightest cluster galaxies (BCGs) are usually quiescent, but many exhibit star formation. Here we exploit the opportunity provided by rest-frame UV imaging of galaxy clusters in the Cluster Lensing and Supernovae with Hubble (CLASH) Multi-Cycle Treasury Project to reveal the diversity of UV morphologies in BCGs and to compare them with recent simulations of the cool, star-forming gas structures produced by precipitation-driven feedback. All of the CLASH BCGs are detected in the rest-frame UV (280 nm), regardless of their star formation activity, because evolved stellar populations produce a modest amount of UV light that traces the relatively smooth, symmetric, and centrally peaked stellar distribution seen in the near infrared. Ultraviolet morphologies among the BCGs with strong UV excesses exhibit distinctive knots, multiple elongated clumps, and extended filaments of emission that distinctly differ from the smooth profiles of the UV-quiet BCGs. These structures, which are similar to those seen in the few star-forming BCGs observed in the UV at low redshift, are suggestive of bi-polar streams of clumpy star formation, but not of spiral arms or large, kiloparsec-scale disks. Based on the number of streams and lack of culprit companion galaxies, these streams are unlikely to have arisen from multiple collisions with gas-rich galaxies. These star-forming UV structures are morphologically similar to the cold-gas structures produced in simulations of precipitation-driven active galactic nucleus feedback in which jets uplift low-entropy gas to greater altitudes, causing it to condense. Unobscured star formation rates estimated from CLASH UV images using the Kennicutt relation range up to 80 {{M}⊙ } y{{r}-1} in the most extended and highly structured systems. The circumgalactic gas-entropy threshold for star formation in CLASH BCGs at z ˜ 0.2-0.5 is indistinguishable from that for clusters at z\\lt 0.2.

  1. TEMPRANILLO Reveals the Mesophyll as Crucial for Epidermal Trichome Formation1[OPEN

    PubMed Central

    Aguilar-Jaramillo, Andrea E.; Osnato, Michela; Shani, Eilon

    2016-01-01

    Plant trichomes are defensive specialized epidermal cells. In all accepted models, the epidermis is the layer involved in trichome formation, a process controlled by gibberellins (GAs) in Arabidopsis rosette leaves. Indeed, GA activates a genetic cascade in the epidermis for trichome initiation. Here we report that TEMPRANILLO (TEM) genes negatively control trichome initiation not only from the epidermis but also from the leaf layer underneath the epidermis, the mesophyll. Plants over-expressing or reducing TEM specifically in the mesophyll, display lower or higher trichome numbers, respectively. We surprisingly found that fluorescently labeled GA3 accumulates exclusively in the mesophyll of leaves, but not in the epidermis, and that TEM reduces its accumulation and the expression of several newly identified GA transporters. This strongly suggests that TEM plays an essential role, not only in GA biosynthesis, but also in regulating GA distribution in the mesophyll, which in turn directs epidermal trichome formation. Moreover, we show that TEM also acts as a link between GA and cytokinin signaling in the epidermis by negatively regulating downstream genes of both trichome formation pathways. Overall, these results call for a re-evaluation of the present theories of trichome formation as they reveal mesophyll essential during epidermal trichome initiation. PMID:26802039

  2. Kinetic analysis reveals the diversity of microscopic mechanisms through which molecular chaperones suppress amyloid formation

    NASA Astrophysics Data System (ADS)

    Arosio, Paolo; Michaels, Thomas C. T.; Linse, Sara; Månsson, Cecilia; Emanuelsson, Cecilia; Presto, Jenny; Johansson, Jan; Vendruscolo, Michele; Dobson, Christopher M.; Knowles, Tuomas P. J.

    2016-03-01

    It is increasingly recognized that molecular chaperones play a key role in modulating the formation of amyloid fibrils, a process associated with a wide range of human disorders. Understanding the detailed mechanisms by which they perform this function, however, has been challenging because of the great complexity of the protein aggregation process itself. In this work, we build on a previous kinetic approach and develop a model that considers pairwise interactions between molecular chaperones and different protein species to identify the protein components targeted by the chaperones and the corresponding microscopic reaction steps that are inhibited. We show that these interactions conserve the topology of the unperturbed reaction network but modify the connectivity weights between the different microscopic steps. Moreover, by analysing several protein-molecular chaperone systems, we reveal the striking diversity in the microscopic mechanisms by which molecular chaperones act to suppress amyloid formation.

  3. Kinetic analysis reveals the diversity of microscopic mechanisms through which molecular chaperones suppress amyloid formation

    PubMed Central

    Arosio, Paolo; Michaels, Thomas C. T.; Linse, Sara; Månsson, Cecilia; Emanuelsson, Cecilia; Presto, Jenny; Johansson, Jan; Vendruscolo, Michele; Dobson, Christopher M.; Knowles, Tuomas P. J.

    2016-01-01

    It is increasingly recognized that molecular chaperones play a key role in modulating the formation of amyloid fibrils, a process associated with a wide range of human disorders. Understanding the detailed mechanisms by which they perform this function, however, has been challenging because of the great complexity of the protein aggregation process itself. In this work, we build on a previous kinetic approach and develop a model that considers pairwise interactions between molecular chaperones and different protein species to identify the protein components targeted by the chaperones and the corresponding microscopic reaction steps that are inhibited. We show that these interactions conserve the topology of the unperturbed reaction network but modify the connectivity weights between the different microscopic steps. Moreover, by analysing several protein-molecular chaperone systems, we reveal the striking diversity in the microscopic mechanisms by which molecular chaperones act to suppress amyloid formation. PMID:27009901

  4. From attitude formation to behavioral response in organ donation: using marketing to increase consent rates.

    PubMed

    Aldridge, Alicia; Guy, Bonnie; Roggenkamp, Susan

    2003-01-01

    This article presents a theoretical analysis of attitude formation and the relationship to stated behavioral intentions as it relates to the decision to donate organs. This analysis reveals the presence of three distinct paths to behavior of potential donors, groups differing in their involvement with organ donation. Promotional objectives and campaign strategies designed to influence attitudes and behaviors should differ according to the behavioral path in operation and the involvement of the audience. Mass media campaigns are likely to reach high involvement groups only. Therefore, personal selling, underutilized in previous donation campaigns, should be brought into the donation strategy to appeal to low involvement groups. By recognizing differences in audience involvement and implementing different strategies, overall donation rates could substantially increase. PMID:15018000

  5. GOODS-Herschel: ultra-deep XMM-Newton observations reveal AGN/star-formation connection

    NASA Astrophysics Data System (ADS)

    Rovilos, E.; Comastri, A.; Gilli, R.; Georgantopoulos, I.; Ranalli, P.; Vignali, C.; Lusso, E.; Cappelluti, N.; Zamorani, G.; Elbaz, D.; Dickinson, M.; Hwang, H. S.; Charmandaris, V.; Ivison, R. J.; Merloni, A.; Daddi, E.; Carrera, F. J.; Brandt, W. N.; Mullaney, J. R.; Scott, D.; Alexander, D. M.; Del Moro, A.; Morrison, G.; Murphy, E. J.; Altieri, B.; Aussel, H.; Dannerbauer, H.; Kartaltepe, J.; Leiton, R.; Magdis, G.; Magnelli, B.; Popesso, P.; Valtchanov, I.

    2012-10-01

    Models of galaxy evolution assume some connection between the AGN and star formation activity in galaxies. We use the multi-wavelength information of the CDFS to assess this issue. We select the AGNs from the 3 Ms XMM-Newton survey and measure the star-formation rates of their hosts using data that probe rest-frame wavelengths longward of 20 μm, predominantly from deep 100 μm and 160 μm Herschel observations, but also from Spitzer-MIPS-70 μm. Star-formation rates are obtained from spectral energy distribution fits, identifying and subtracting an AGN component. Our sample consists of sources in the z ≈ 0.5-4 redshift range, with star-formation rates SFR ≈ 101-103 M⊙ yr-1 and stellar masses M⋆ ≈ 1010-1011.5 M⊙. We divide the star-formation rates by the stellar masses of the hosts to derive specific star-formation rates (sSFR) and find evidence for a positive correlation between the AGN activity (proxied by the X-ray luminosity) and the sSFR for themost active systems with X-ray luminosities exceeding Lx ≃ 1043 erg s-1 and redshifts z ≳ 1. We do not find evidence for such a correlation for lower luminosity systems or those at lower redshifts, consistent with previous studies. We do not find any correlation between the SFR (or the sSFR) and the X-ray absorption derived from high-quality XMM-Newton spectra either, showing that the absorption is likely to be linked to the nuclear region rather than the host, while the star-formation is not nuclear. Comparing the sSFR of the hosts to the characteristic sSFR of star-forming galaxies at the same redshift (the so-called "main sequence") we find that the AGNs reside mostly in main-sequence and starburst hosts, reflecting the AGN-sSFR connection; however the infrared selection might bias this result. Limiting our analysis to the highest X-ray luminosity AGNs (X-ray QSOs with Lx > 1044 erg s-1), we find that the highest-redshift QSOs (with z ≳ 2) reside predominantly in starburst hosts, with an average s

  6. SNLS: Type Ia Supernova Rates from the SNLS Survey: the Connection with Morphology and Star Formation Rate

    NASA Astrophysics Data System (ADS)

    Pritchet, C. J.; Sullivan, M.; Gwyn, S.; Astier, P.; Aubourg, E.; Balam, D.; Basa, S.; Carlberg, R. G.; Conley, A.; Fabbro, S.; Fouchez, D.; Guy, J.; Hook, I.; Howell, D. A.; Lafoux, H.; Neill, J. D.; Pain, R.; Palanque-Delabrouille, N.; Perrett, K.; Regnault, N.; Rich, J.; Taillet, R.; Baumont, S.; Bronder, J.; Lusset, V.; Ripoche, P.; Mourao, A.; Perlmutter, S.; Graham, M.; Hsiao, E.

    2005-12-01

    Analysis of 150 SNLS Survey Type Ia supernovae (0.2 < z < 0.9, all with spectroscopic identification) shows a strong connection between SNIa rate, normalized per unit mass, and star formation rate or galaxy morphology. This correlation is in the sense that the rate per unit mass in Irr galaxies is more than a factor of 10 higher than that in E/S0 galaxies. This result independently confirms that found for SNLS SNeIa by Sullivan et al (this meeting), but makes use of different photometric redshifts for the field population (Gwyn et al. 2005), and different M/L and star formation rate estimators. The SFR/morphology dependence of SNIa rate is, to first order, independent of redshift. The observations can be explained in terms of one or two component models for the origin of SNeIa (Howell et al., this meeting).

  7. Trace incorporation of heavy water reveals slow and heterogeneous pathogen growth rates in cystic fibrosis sputum

    NASA Astrophysics Data System (ADS)

    Kopf, Sebastian H.; Sessions, Alex L.; Cowley, Elise S.; Reyes, Carmen; Van Sambeek, Lindsey; Hu, Yang; Orphan, Victoria J.; Kato, Roberta; Newman, Dianne K.

    2016-01-01

    Effective treatment for chronic infections is undermined by a significant gap in understanding of the physiological state of pathogens at the site of infection. Chronic pulmonary infections are responsible for the morbidity and mortality of millions of immunocompromised individuals worldwide, yet drugs that are successful in laboratory culture are far less effective against pathogen populations persisting in vivo. Laboratory models, upon which preclinical development of new drugs is based, can only replicate host conditions when we understand the metabolic state of the pathogens and the degree of heterogeneity within the population. In this study, we measured the anabolic activity of the pathogen Staphylococcus aureus directly in the sputum of pediatric patients with cystic fibrosis (CF), by combining the high sensitivity of isotope ratio mass spectrometry with a heavy water labeling approach to capture the full range of in situ growth rates. Our results reveal S. aureus generation times with a median of 2.1 d, with extensive growth rate heterogeneity at the single-cell level. These growth rates are far below the detection limit of previous estimates of CF pathogen growth rates, and the rates are slowest in acutely sick patients undergoing pulmonary exacerbations; nevertheless, they are accessible to experimental replication within laboratory models. Treatment regimens that include specific antibiotics (vancomycin, piperacillin/tazobactam, tobramycin) further appear to correlate with slow growth of S. aureus on average, but follow-up longitudinal studies must be performed to determine whether this effect holds for individual patients.

  8. Seasonal determinations of algal virus decay rates reveal overwintering in a temperate freshwater pond.

    PubMed

    Long, Andrew M; Short, Steven M

    2016-07-01

    To address questions about algal virus persistence (i.e., continued existence) in the environment, rates of decay of infectivity for two viruses that infect Chlorella-like algae, ATCV-1 and CVM-1, and a virus that infects the prymnesiophyte Chrysochromulina parva, CpV-BQ1, were estimated from in situ incubations in a temperate, seasonally frozen pond. A series of experiments were conducted to estimate rates of decay of infectivity in all four seasons with incubations lasting 21 days in spring, summer and autumn, and 126 days in winter. Decay rates observed across this study were relatively low compared with previous estimates obtained for other algal viruses, and ranged from 0.012 to 11% h(-1). Overall, the virus CpV-BQ1 decayed most rapidly whereas ATCV-1 decayed most slowly, but for all viruses the highest decay rates were observed during the summer and the lowest were observed during the winter. Furthermore, the winter incubations revealed the ability of each virus to overwinter under ice as ATCV-1, CVM-1 and CpV-BQ1 retained up to 48%, 19% and 9% of their infectivity after 126 days, respectively. The observed resilience of algal viruses in a seasonally frozen freshwater pond provides a mechanism that can support the maintenance of viral seed banks in nature. However, the high rates of decay observed in the summer demonstrate that virus survival and therefore environmental persistence can be subject to seasonal bottlenecks. PMID:26943625

  9. Trace incorporation of heavy water reveals slow and heterogeneous pathogen growth rates in cystic fibrosis sputum

    PubMed Central

    Kopf, Sebastian H.; Sessions, Alex L.; Cowley, Elise S.; Reyes, Carmen; Van Sambeek, Lindsey; Hu, Yang; Orphan, Victoria J.; Kato, Roberta; Newman, Dianne K.

    2016-01-01

    Effective treatment for chronic infections is undermined by a significant gap in understanding of the physiological state of pathogens at the site of infection. Chronic pulmonary infections are responsible for the morbidity and mortality of millions of immunocompromised individuals worldwide, yet drugs that are successful in laboratory culture are far less effective against pathogen populations persisting in vivo. Laboratory models, upon which preclinical development of new drugs is based, can only replicate host conditions when we understand the metabolic state of the pathogens and the degree of heterogeneity within the population. In this study, we measured the anabolic activity of the pathogen Staphylococcus aureus directly in the sputum of pediatric patients with cystic fibrosis (CF), by combining the high sensitivity of isotope ratio mass spectrometry with a heavy water labeling approach to capture the full range of in situ growth rates. Our results reveal S. aureus generation times with a median of 2.1 d, with extensive growth rate heterogeneity at the single-cell level. These growth rates are far below the detection limit of previous estimates of CF pathogen growth rates, and the rates are slowest in acutely sick patients undergoing pulmonary exacerbations; nevertheless, they are accessible to experimental replication within laboratory models. Treatment regimens that include specific antibiotics (vancomycin, piperacillin/tazobactam, tobramycin) further appear to correlate with slow growth of S. aureus on average, but follow-up longitudinal studies must be performed to determine whether this effect holds for individual patients. PMID:26715741

  10. Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation.

    PubMed

    Shiraiwa, Manabu; Yee, Lindsay D; Schilling, Katherine A; Loza, Christine L; Craven, Jill S; Zuend, Andreas; Ziemann, Paul J; Seinfeld, John H

    2013-07-16

    Organic aerosols are ubiquitous in the atmosphere and play a central role in climate, air quality, and public health. The aerosol size distribution is key in determining its optical properties and cloud condensation nucleus activity. The dominant portion of organic aerosol is formed through gas-phase oxidation of volatile organic compounds, so-called secondary organic aerosols (SOAs). Typical experimental measurements of SOA formation include total SOA mass and atomic oxygen-to-carbon ratio. These measurements, alone, are generally insufficient to reveal the extent to which condensed-phase reactions occur in conjunction with the multigeneration gas-phase photooxidation. Combining laboratory chamber experiments and kinetic gas-particle modeling for the dodecane SOA system, here we show that the presence of particle-phase chemistry is reflected in the evolution of the SOA size distribution as well as its mass concentration. Particle-phase reactions are predicted to occur mainly at the particle surface, and the reaction products contribute more than half of the SOA mass. Chamber photooxidation with a midexperiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. Although experiments need to be conducted with other SOA precursor hydrocarbons, current results demonstrate coupling between particle-phase chemistry and size distribution dynamics in the formation of SOAs, thereby opening up an avenue for analysis of the SOA formation process. PMID:23818634

  11. Magnetite: What it reveals about the origin of the banded iron formations. [Abstract only

    NASA Technical Reports Server (NTRS)

    Schwartz, D. E.; Mancinelli, R. L.; White, M. R.

    1994-01-01

    Magnetite, Fe3O4 is produced abiotically and biotically. Abiotically, magnetite is a late magmatic mineral and forms as a consequence of the cooling of iron rich magma. Biotically, magnetite is produced by several organisms, including magnetotactic bacteria. Hematite, Fe2O3, is also produced abiotically and biotically. Abiotically, hematite rarely occurs as a primary mineral in igneous rocks, but is common as an alteration product, fumarole deposit, and in some metamorphosed Fe-rich rocks. Biotically, hematite is produced by several types of microorganisms. Biologically-produced magnetite and hematite are formed under the control of the host organism, and consequently, have characteristics not found in abiotically produced magnetite and hematite crystals. To determine if the magnetite and hematite in the Banded Iron Formation was biologically or abiotically produced, the characteristics of biologically-produced magnetite and hematite (concentrated from Aquaspirillum magnetotacticum) and abiotically-produced magnetite and hematite obtained from Wards Scientific Supply Company, were compared with characteristics of magnetite and hematite concentrated from the Gunflint Banded Iron Formation (Ontario, Canada) using thermal and crystallographic analytical techniques. Whole rock analysis of the Gunflint Banded Iron Formation by x-ray diffraction (XRD) and differential thermal analysis (DTA) revealed the presence of quartz, hematite, siderite and dolomite as the major minerals, and magnetite, greenalite, pyrite, pyrrhotite and apatite as the minor minerals. Analysis of a crude magnetic fraction of the Gunflint showed the minerals quartz, hematite, siderite, dolomite, and magnetite. Analysis of the crude magnetic fraction from Aquaspirillum magnetotacticum revealed organic compounds plus hematite and magnetite. The mineral identification and particle size distribution data obtained from the DTA along with XRD data indicate that the magnetite and hematite from the Gunflint

  12. Isolation of Hox cluster genes from insects reveals an accelerated sequence evolution rate.

    PubMed

    Hadrys, Heike; Simon, Sabrina; Kaune, Barbara; Schmitt, Oliver; Schöner, Anja; Jakob, Wolfgang; Schierwater, Bernd

    2012-01-01

    Among gene families it is the Hox genes and among metazoan animals it is the insects (Hexapoda) that have attracted particular attention for studying the evolution of development. Surprisingly though, no Hox genes have been isolated from 26 out of 35 insect orders yet, and the existing sequences derive mainly from only two orders (61% from Hymenoptera and 22% from Diptera). We have designed insect specific primers and isolated 37 new partial homeobox sequences of Hox cluster genes (lab, pb, Hox3, ftz, Antp, Scr, abd-a, Abd-B, Dfd, and Ubx) from six insect orders, which are crucial to insect phylogenetics. These new gene sequences provide a first step towards comparative Hox gene studies in insects. Furthermore, comparative distance analyses of homeobox sequences reveal a correlation between gene divergence rate and species radiation success with insects showing the highest rate of homeobox sequence evolution. PMID:22685537

  13. Hα star formation rates of z > 1 galaxy clusters in the IRAC shallow cluster survey

    SciTech Connect

    Zeimann, Gregory R.; Stanford, S. A.; Brodwin, Mark; Gonzalez, Anthony H.; Mancone, Conor; Snyder, Gregory F.; Stern, Daniel; Eisenhardt, Peter; Dey, Arjun; Moustakas, John

    2013-12-20

    We present Hubble Space Telescope near-IR spectroscopy for 18 galaxy clusters at 1.0 formation rates within a projected radius of 500 kpc, and many of our clusters (∼60%) have significant levels of star formation within a projected radius of 200 kpc. A stacking analysis reveals that dust reddening in these star-forming galaxies is positively correlated with stellar mass and may be higher in the field than the cluster at a fixed stellar mass. This may indicate a lower amount of gas in star-forming cluster galaxies than in the field population. Also, Hα equivalent widths of star-forming galaxies in the cluster environment are still suppressed below the level of the field. This suppression is most significant for lower mass galaxies (log M {sub *} < 10.0 M {sub ☉}). We therefore conclude that environmental effects are still important at 1.0

  14. Complex fluid flow revealed by monitoring CO2 injection in a fluvial formation

    NASA Astrophysics Data System (ADS)

    Lu, Jiemin; Cook, Paul J.; Hosseini, Seyyed A.; Yang, Changbing; Romanak, Katherine D.; Zhang, Tongwei; Freifeld, Barry M.; Smyth, Rebecca C.; Zeng, Hongliu; Hovorka, Susan D.

    2012-03-01

    At Cranfield, Mississippi, United States, a large-scale carbon dioxide (CO2) injection through an injection well (˜3,080 m deep) was continuously monitored using U-tube samplers in two observation wells located 68 and 112 m east of the injector. The Lower Tuscaloosa Formation injection zone, which consists of amalgamated fluvial point-bar and channel-fill deposits, presents an interesting environment for studying fluid flow in heterogeneous formations. Continual fluid sampling was carried out during the first month of CO2 injection. Two subsequent tracer tests using sulfur hexafluoride (SF6) and krypton were conducted at different injection rates to measure flow velocity change. The field observations showed significant heterogeneity of fluid flow and for the first time clearly demonstrated that fluid flow evolved with time and injection rate. It was found the wells were connected through numerous, separate flow pathways. CO2 flowed through an increasing fraction of the reservoir and sweep efficiency improved with time. The field study also first documented in situ component exchange between brine and gas phases during CO2 injection. It was found that CH4 degassed from brine and is enriched along the gas-water contact. Multiple injectate flow fronts with high CH4 concentration arrived at different times and led to gas composition fluctuations in the observation wells. The findings provide valuable insights into heterogeneous multiphase flow in rock formations and show that conventional geological models and static fluid flow simulations are unable to fully describe the heterogeneous and dynamic flow during fluid injection.

  15. Molecular mechanisms of NET formation and degradation revealed by intravital imaging in the liver vasculature.

    PubMed

    Kolaczkowska, Elzbieta; Jenne, Craig N; Surewaard, Bas G J; Thanabalasuriar, Ajitha; Lee, Woo-Yong; Sanz, Maria-Jesus; Mowen, Kerri; Opdenakker, Ghislain; Kubes, Paul

    2015-01-01

    Neutrophil extracellular traps (NETs) composed of DNA decorated with histones and proteases trap and kill bacteria but also injure host tissue. Here we show that during a bloodstream infection with methicillin-resistant Staphylococcus aureus, the majority of bacteria are sequestered immediately by hepatic Kupffer cells, resulting in transient increases in liver enzymes, focal ischaemic areas and a robust neutrophil infiltration into the liver. The neutrophils release NETs into the liver vasculature, which remain anchored to the vascular wall via von Willebrand factor and reveal significant neutrophil elastase (NE) proteolytic activity. Importantly, DNase although very effective at DNA removal, and somewhat effective at inhibiting NE proteolytic activity, fails to remove the majority of histones from the vessel wall and only partly reduces injury. By contrast, inhibition of NET production as modelled by PAD4-deficiency, or prevention of NET formation and proteolytic activity as modelled in NE(-/-) mice prevent collateral host tissue damage. PMID:25809117

  16. Molecular mechanisms of NET formation and degradation revealed by intravital imaging in the liver vasculature

    PubMed Central

    Kolaczkowska, Elzbieta; Jenne, Craig N.; Surewaard, Bas G. J.; Thanabalasuriar, Ajitha; Lee, Woo-Yong; Sanz, Maria-Jesus; Mowen, Kerri; Opdenakker, Ghislain; Kubes, Paul

    2015-01-01

    Neutrophil extracellular traps (NETs) composed of DNA decorated with histones and proteases trap and kill bacteria but also injure host tissue. Here we show that during a bloodstream infection with methicillin-resistant Staphylococcus aureus, the majority of bacteria are sequestered immediately by hepatic Kupffer cells, resulting in transient increases in liver enzymes, focal ischaemic areas and a robust neutrophil infiltration into the liver. The neutrophils release NETs into the liver vasculature, which remain anchored to the vascular wall via von Willebrand factor and reveal significant neutrophil elastase (NE) proteolytic activity. Importantly, DNase although very effective at DNA removal, and somewhat effective at inhibiting NE proteolytic activity, fails to remove the majority of histones from the vessel wall and only partly reduces injury. By contrast, inhibition of NET production as modelled by PAD4-deficiency, or prevention of NET formation and proteolytic activity as modelled in NE−/− mice prevent collateral host tissue damage. PMID:25809117

  17. Metatranscriptomics reveals the molecular mechanism of large granule formation in granular anammox reactor

    PubMed Central

    Bagchi, Samik; Lamendella, Regina; Strutt, Steven; Van Loosdrecht, Mark C. M.; Saikaly, Pascal E.

    2016-01-01

    Granules enriched with anammox bacteria are essential in enhancing the treatment of ammonia-rich wastewater, but little is known about how anammox bacteria grow and multiply inside granules. Here, we combined metatranscriptomics, quantitative PCR and 16S rRNA gene sequencing to study the changes in community composition, metabolic gene content and gene expression in a granular anammox reactor with the objective of understanding the molecular mechanism of anammox growth and multiplication that led to formation of large granules. Size distribution analysis revealed the spatial distribution of granules in which large granules having higher abundance of anammox bacteria (genus Brocadia) dominated the bottom biomass. Metatranscriptomics analysis detected all the essential transcripts for anammox metabolism. During the later stage of reactor operation, higher expression of ammonia and nitrite transport proteins and key metabolic enzymes mainly in the bottom large granules facilitated anammox bacteria activity. The high activity resulted in higher growth and multiplication of anammox bacteria and expanded the size of the granules. This conceptual model for large granule formation proposed here may assist in the future design of anammox processes for mainstream wastewater treatment. PMID:27319320

  18. Metatranscriptomics reveals the molecular mechanism of large granule formation in granular anammox reactor.

    PubMed

    Bagchi, Samik; Lamendella, Regina; Strutt, Steven; Van Loosdrecht, Mark C M; Saikaly, Pascal E

    2016-01-01

    Granules enriched with anammox bacteria are essential in enhancing the treatment of ammonia-rich wastewater, but little is known about how anammox bacteria grow and multiply inside granules. Here, we combined metatranscriptomics, quantitative PCR and 16S rRNA gene sequencing to study the changes in community composition, metabolic gene content and gene expression in a granular anammox reactor with the objective of understanding the molecular mechanism of anammox growth and multiplication that led to formation of large granules. Size distribution analysis revealed the spatial distribution of granules in which large granules having higher abundance of anammox bacteria (genus Brocadia) dominated the bottom biomass. Metatranscriptomics analysis detected all the essential transcripts for anammox metabolism. During the later stage of reactor operation, higher expression of ammonia and nitrite transport proteins and key metabolic enzymes mainly in the bottom large granules facilitated anammox bacteria activity. The high activity resulted in higher growth and multiplication of anammox bacteria and expanded the size of the granules. This conceptual model for large granule formation proposed here may assist in the future design of anammox processes for mainstream wastewater treatment. PMID:27319320

  19. Metatranscriptomics reveals the molecular mechanism of large granule formation in granular anammox reactor

    NASA Astrophysics Data System (ADS)

    Bagchi, Samik; Lamendella, Regina; Strutt, Steven; van Loosdrecht, Mark C. M.; Saikaly, Pascal E.

    2016-06-01

    Granules enriched with anammox bacteria are essential in enhancing the treatment of ammonia-rich wastewater, but little is known about how anammox bacteria grow and multiply inside granules. Here, we combined metatranscriptomics, quantitative PCR and 16S rRNA gene sequencing to study the changes in community composition, metabolic gene content and gene expression in a granular anammox reactor with the objective of understanding the molecular mechanism of anammox growth and multiplication that led to formation of large granules. Size distribution analysis revealed the spatial distribution of granules in which large granules having higher abundance of anammox bacteria (genus Brocadia) dominated the bottom biomass. Metatranscriptomics analysis detected all the essential transcripts for anammox metabolism. During the later stage of reactor operation, higher expression of ammonia and nitrite transport proteins and key metabolic enzymes mainly in the bottom large granules facilitated anammox bacteria activity. The high activity resulted in higher growth and multiplication of anammox bacteria and expanded the size of the granules. This conceptual model for large granule formation proposed here may assist in the future design of anammox processes for mainstream wastewater treatment.

  20. The rate of formation of clusters on the surface of the comet's nucleus

    NASA Astrophysics Data System (ADS)

    Shoyokubov, Shoayub

    2016-07-01

    The paper describes the positive and negative clusters ions formation rate on the surface of comet nucleus under the influence of corpuscular solar wind particles taking into account the experimentally calculated coefficients of secondary ion emission.

  1. Cloud Evolution during Tropical Cyclone Formation as Revealed by TRMM PR

    NASA Astrophysics Data System (ADS)

    Fritz, C.; Wang, Z.; Nesbitt, S. W.; Dunkerton, T. J.

    2015-12-01

    To understand the cloud evolution during tropical cyclone formation, cloud features for more than 100 named tropical cyclones over the Atlantic are examined from the tropical wave to the tropical cyclone stage using the TRMM Precipitation Radar (PR). We focus on a time window from 3 days before genesis to 1 day after genesis, where the diagnoses for the pre-genesis evolution are carried out in the framework of the marsupial paradigm and the post-genesis analysis using the NHC best-tracks. The 20 dBZ echo-top height is used in combination with the near surface rain rate to identify the different types of convection: i) shallow convection; ii) mid-level convection and iii) deep convection. The frequency of occurrence for each precipitation type is calculated, and the relative contributions of different types of precipitation to the total rain rate are examined with respect to the center. Precipitation was found to increase in coverage and intensity near the wave-pouch center approaching genesis. Stratiform precipitation is prevalent from day -3 to day +1, but convective precipitation persistently increases near the inner-core. Mid-level convection occurs more frequently than deep convection from day -3 to day +1 and makes a larger contribution to the total precipitation than deep convection. It is also shown that stratiform precipitation, mid-level convection and deep convection all contribute to the substantial increase in rain-rate.

  2. Effect of Booklet/Folder Questionnaire Format and Style of Type on Mail Survey Response Rates.

    ERIC Educational Resources Information Center

    Boser, Judith A.

    Results of two studies, involving surveys of alumni of postsecondary institutions, are presented to assess the effect of format and typeface on mail survey response rates. The first study focused on the effect of booklet/folder format versus stapled sheets. The method of reproduction, page content, page size, and appearance of the questionnaires…

  3. Multiperspective smFRET reveals rate-determining late intermediates of ribosomal translocation.

    PubMed

    Wasserman, Michael R; Alejo, Jose L; Altman, Roger B; Blanchard, Scott C

    2016-04-01

    Directional translocation of the ribosome through the mRNA open reading frame is a critical determinant of translational fidelity. This process entails a complex interplay of large-scale conformational changes within the actively translating particle, which together coordinate the movement of tRNA and mRNA substrates with respect to the large and small ribosomal subunits. Using pre-steady state, single-molecule fluorescence resonance energy transfer imaging, we tracked the nature and timing of these conformational events within the Escherichia coli ribosome from five structural perspectives. Our investigations revealed direct evidence of structurally and kinetically distinct late intermediates during substrate movement, whose resolution determines the rate of translocation. These steps involve intramolecular events within the EF-G-GDP-bound ribosome, including exaggerated, reversible fluctuations of the small-subunit head domain, which ultimately facilitate peptidyl-tRNA's movement into its final post-translocation position. PMID:26926435

  4. STAR FORMATION RATES IN MOLECULAR CLOUDS AND THE NATURE OF THE EXTRAGALACTIC SCALING RELATIONS

    SciTech Connect

    Lada, Charles J.; Forbrich, Jan; Lombardi, Marco; Alves, Joao F. E-mail: jforbrich@cfa.harvard.edu E-mail: joao.alves@univie.ac.at

    2012-02-01

    In this paper, we investigate scaling relations between star formation rates and molecular gas masses for both local Galactic clouds and a sample of external galaxies. We specifically consider relations between the star formation rates and measurements of dense, as well as total, molecular gas masses. We argue that there is a fundamental empirical scaling relation that directly connects the local star formation process with that operating globally within galaxies. Specifically, the total star formation rate in a molecular cloud or galaxy is linearly proportional to the mass of dense gas within the cloud or galaxy. This simple relation, first documented in previous studies, holds over a span of mass covering nearly nine orders of magnitude and indicates that the rate of star formation is directly controlled by the amount of dense molecular gas that can be assembled within a star formation complex. We further show that the star formation rates and total molecular masses, characterizing both local clouds and galaxies, are correlated over similarly large scales of mass and can be described by a family of linear star formation scaling laws, parameterized by f{sub DG}, the fraction of dense gas contained within the clouds or galaxies. That is, the underlying star formation scaling law is always linear for clouds and galaxies with the same dense gas fraction. These considerations provide a single unified framework for understanding the relation between the standard (nonlinear) extragalactic Schmidt-Kennicutt scaling law, that is typically derived from CO observations of the gas, and the linear star formation scaling law derived from HCN observations of the dense gas.

  5. Varying relative degradation rates of oil in different forms and environments revealed by ramped pyrolysis.

    PubMed

    Pendergraft, Matthew A; Rosenheim, Brad E

    2014-09-16

    Degradation of oil contamination yields stabilized products by removing and transforming reactive and volatile compounds. In contaminated coastal environments, the processes of degradation are influenced by shoreline energy, which increases the surface area of the oil as well as exchange between oil, water, sediments, microbes, oxygen, and nutrients. Here, a ramped pyrolysis carbon isotope technique is employed to investigate thermochemical and isotopic changes in organic material from coastal environments contaminated with oil from the 2010 BP Deepwater Horizon oil spill. Oiled beach sediment, tar ball, and marsh samples were collected from a barrier island and a brackish marsh in southeast Louisiana over a period of 881 days. Stable carbon ((13)C) and radiocarbon ((14)C) isotopic data demonstrate a predominance of oil-derived carbon in the organic material. Ramped pyrolysis profiles indicate that the organic material was transformed into more stable forms. Our data indicate relative rates of stabilization in the following order, from fastest to slowest: high energy beach sediments > low energy beach sediments > marsh > tar balls. Oil was transformed most rapidly where shoreline energy and the rates of oil dispersion and exchange with water, sediments, microbes, oxygen, and nutrients were greatest. Still, isotope data reveal persistence of oil. PMID:25105342

  6. 40 CFR Table I-13 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Electronics... Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for LCD Manufacturing for Use With...) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for LCD Manufacturing for...

  7. 40 CFR Table I-14 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Electronics... Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for PV Manufacturing for Use With...) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for PV Manufacturing for...

  8. 40 CFR Table I-15 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for MEMS Manufacturing for Use With...) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for MEMS Manufacturing for...

  9. 40 CFR Table I-3 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for Semiconductor Manufacturing for... Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for Semiconductor Manufacturing...

  10. 40 CFR Table I-3 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for Semiconductor Manufacturing for... Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for...

  11. 40 CFR Table I-4 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for Semiconductor Manufacturing for... Factors(1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for...

  12. Migration rates and formation injectivity to determine containment time scales of sequestered carbon dioxide

    USGS Publications Warehouse

    Burke, Lauri

    2012-01-01

    Additionally, this research establishes a methodology to calculate the injectivity of a target formation. Because injectivity describes the pressure increase due to the introduction of fluids into a formation, the relevant application of injectivity is to determine the pressure increase, due to an injection volume and flow rate, that will induce fractures in the reservoir rocks. This quantity is defined mathematically as the maximum pressure differential between the hydrostatic gradient and the fracture gradient of the target formation. Injectivity is mathematically related to the maximum pressure differential of the formation, and can be used to determine the upper limit for the pressure increase that an injection target can withstand before fracturing.

  13. DNA fingerprinting reveals elevated mutation rates in herring gulls inhabiting a genotoxically contaminated site

    SciTech Connect

    Yauk, C.L.; Quinn, J.S.

    1995-12-31

    The authors used multi-locus DNA fingerprinting to examine families of herring gulls (Larus argentatus) from a genotoxically contaminated site (Hamilton Harbour) and from a pristine location (Kent Island, Bay of Fundy) to show significant differences in mutation rates between the locations. Overall the authors identified 17 mutant bands from 15 individuals of the 35 examined from Hamilton Harbour, and 7 mutant fragments from 7 individuals, of the 43 examined from Kent Island; a mutation frequency of 0.429 per nestling for Hamilton Harbour and 0.163 for Kent Island. The total number of individuals with mutant bands was significantly higher at Hamilton Harbour than at Kent Island (X{sup 2}=6.734; df = 1; P < 0.01). Ongoing analysis of other less contaminated sites also reveals lower mutation rates than those seen in Hamilton Harbour. With multi-locus DNA fingerprinting many regions of the genome can be surveyed simultaneously. The tandemly repeated arrays of nucleotides examined with DNA fingerprinting are known to have elevated rates of mutation. Furthermore, the mutations seen with DNA fingerprinting are predominantly heritable. Other biomarkers currently used in situ are not able to monitor direct and heritable DNA mutation, or measure biological endpoints that frequently result in spontaneous abortion creating difficulty in observing significantly elevated levels in viable offspring. The authors suggest that multilocus DNA fingerprinting can be used as a biomarker to identify potentially heritable risks before the onset of other types of ecological damage. This approach provides a direct measure of mutation in situ and in vivo in a vertebrate species under ambient conditions.

  14. GAPS IN THE HD 169142 PROTOPLANETARY DISK REVEALED BY POLARIMETRIC IMAGING: SIGNS OF ONGOING PLANET FORMATION?

    SciTech Connect

    Quanz, Sascha P.; Avenhaus, Henning; Garufi, Antonio; Schmid, Hans Martin; Buenzli, Esther; Wolf, Sebastian

    2013-03-20

    We present H-band Very Large Telescope/NACO polarized light images of the Herbig Ae/Be star HD 169142 probing its protoplanetary disk as close as {approx}0.''1 to the star. Our images trace the face-on disk out to {approx}1.''7 ({approx}250 AU) and reveal distinct substructures for the first time: (1) the inner disk ({approx}<20 AU) appears to be depleted in scattering dust grains; (2) an unresolved disk rim is imaged at {approx}25 AU; (3) an annular gap extends from {approx}40 to 70 AU; (4) local brightness asymmetries are found on opposite sides of the annular gap. We discuss different explanations for the observed morphology among which ongoing planet formation is a tempting, but yet to be proven, one. Outside of {approx}85 AU the surface brightness drops off roughly {proportional_to}r {sup -3.3}, but describing the disk regions between 85-120 AU and 120-250 AU separately with power laws {proportional_to}r {sup -2.6} and {proportional_to}r {sup -3.9} provides a better fit hinting toward another discontinuity in the disk surface. The flux ratio between the disk-integrated polarized light and the central star is {approx}4.1 Multiplication-Sign 10{sup -3}. Finally, combining our results with those from the literature, {approx}40% of the scattered light in the H band appears to be polarized. Our results emphasize that HD 169142 is an interesting system for future planet formation or disk evolution studies.

  15. Surface Polysaccharide Mutants Reveal that Absence of O Antigen Reduces Biofilm Formation of Actinobacillus pleuropneumoniae

    PubMed Central

    Hathroubi, S.; Hancock, M. A.; Langford, P. R.; Tremblay, Y. D. N.; Labrie, J.

    2015-01-01

    Actinobacillus pleuropneumoniae is a Gram-negative bacterium belonging to the Pasteurellaceae family and the causative agent of porcine pleuropneumonia, a highly contagious lung disease causing important economic losses. Surface polysaccharides, including lipopolysaccharides (LPS) and capsular polysaccharides (CPS), are implicated in the adhesion and virulence of A. pleuropneumoniae, but their role in biofilm formation is still unclear. In this study, we investigated the requirement for these surface polysaccharides in biofilm formation by A. pleuropneumoniae serotype 1. Well-characterized mutants were used: an O-antigen LPS mutant, a truncated core LPS mutant with an intact O antigen, a capsule mutant, and a poly-N-acetylglucosamine (PGA) mutant. We compared the amount of biofilm produced by the parental strain and the isogenic mutants using static and dynamic systems. Compared to the findings for the biofilm of the parental or other strains, the biofilm of the O antigen and the PGA mutants was dramatically reduced, and it had less cell-associated PGA. Real-time PCR analyses revealed a significant reduction in the level of pgaA, cpxR, and cpxA mRNA in the biofilm cells of the O-antigen mutant compared to that in the biofilm cells of the parental strain. Specific binding between PGA and LPS was consistently detected by surface plasmon resonance, but the lack of O antigen did not abolish these interactions. In conclusion, the absence of the O antigen reduces the ability of A. pleuropneumoniae to form a biofilm, and this is associated with the reduced expression and production of PGA. PMID:26483403

  16. Properties of Outflows from Dwarf Galaxies: Insights into the Evolution of the Star Formation Rate

    NASA Astrophysics Data System (ADS)

    Martin, C. L.

    1997-12-01

    Stellar winds and supernovae from massive stars have a strong impact on the interstellar medium. In dwarf galaxies, for example, the supernova explosions following a burst of star formation are predicted to drive any remaining interstellar gas out of the galaxy (Larson 1974; Dekel & Silk 1986). Uncertainties about the role of this feedback process -- and related but less violent activity -- in regulating the star formation rate in a galaxy pose a critical problem for theories of galaxy formation and evolution. I will present measurements of disk mass-loss rates in 15 nearby dwarf galaxies, examine the efficiency of mass ejection relative to the star formation rate, and discuss the effect of the halo potential on the fate of the outflowing gas.

  17. Evidence of reaction rate influencing cubic and hexagonal phase formation process in CdS nanocrystals

    NASA Astrophysics Data System (ADS)

    Deka, Kuldeep; Kalita, M. P. C.

    2016-05-01

    CdS nanocrystals are synthesized by co-precipitation method using 2-mercaptoethanol (ME) as capping agent. Cubic, hexagonal and their mixture are obtained by varying the ME concentration. Lower (higher) ME concentration results in cubic (hexagonal) phase. The crystallite sizes are in the range 3-7 nm. Increase in ME concentration lead to lower reaction rate between Cd2+ and S2- of the precursors, and slower reaction rate is found to favor hexagonal phase formation over the cubic one in CdS nanocrystals. Role of reaction rate in the phase formation process provides a way to synthesize CdS nanocrystals in desired crystal phase.

  18. The effect of fission products on the rate of U3O8 formation in SIMFUEL oxidized in air at 250°C

    NASA Astrophysics Data System (ADS)

    Choi, Jong-Won; McEachern, Rod J.; Taylor, Peter; Wood, Donald D.

    1996-06-01

    The effect of fission products on the rate of U3O8 formation was investigated by oxidizing UO2-based SIMFUEL (simulated high burnup nuclear fuel) and unirradiated UO2 fuel specimens in air at 250°C for different times (1-317 days). The progress of oxidation was monitored by X-ray diffraction, revealing that the rate of U3O8 formation declines with increasing burnup. An expression was derived to describe quantitatively the time for U3O8 powder formation as a function of simulated burnup. These findings were supported by additional isochronal oxidation experiments conducted between 200 and 300°C.

  19. Decameric SelA•tRNA(Sec) ring structure reveals mechanism of bacterial selenocysteine formation.

    PubMed

    Itoh, Yuzuru; Bröcker, Markus J; Sekine, Shun-ichi; Hammond, Gifty; Suetsugu, Shiro; Söll, Dieter; Yokoyama, Shigeyuki

    2013-04-01

    The 21st amino acid, selenocysteine (Sec), is synthesized on its cognate transfer RNA (tRNA(Sec)). In bacteria, SelA synthesizes Sec from Ser-tRNA(Sec), whereas in archaea and eukaryotes SepSecS forms Sec from phosphoserine (Sep) acylated to tRNA(Sec). We determined the crystal structures of Aquifex aeolicus SelA complexes, which revealed a ring-shaped homodecamer that binds 10 tRNA(Sec) molecules, each interacting with four SelA subunits. The SelA N-terminal domain binds the tRNA(Sec)-specific D-arm structure, thereby discriminating Ser-tRNA(Sec) from Ser-tRNA(Ser). A large cleft is created between two subunits and accommodates the 3'-terminal region of Ser-tRNA(Sec). The SelA structures together with in vivo and in vitro enzyme assays show decamerization to be essential for SelA function. SelA catalyzes pyridoxal 5'-phosphate-dependent Sec formation involving Arg residues nonhomologous to those in SepSecS. Different protein architecture and substrate coordination of the bacterial enzyme provide structural evidence for independent evolution of the two Sec synthesis systems present in nature. PMID:23559248

  20. A Model for Variable Levee Formation Rates in an Active Lava Flow

    NASA Technical Reports Server (NTRS)

    Glaze, L. S.; Baloga, S. M.; Mouginis-Mark, P.; Crisp, J.

    2004-01-01

    Channelized lava flows on Mars and the Earth often feature levees and collateral margins that change in volume along the path of the flow. Consistent with field observations of terrestrial flows, this suggests that the rate of levee formation varies with distance and other factors. Previous models have assumed a constant rate of levee growth, specified by a single parameter, lambda. The rate of levee formation for lava flows is a good indicator of the mass eruption rate and rheology of the flow. Insight into levee formation will help us better understand whether or not the effusion rate was constant during an eruption, and once local topography is considered, allows us to look at cooling and/or rheology changes downslope. Here we present a more realistic extension of the levee formation model that treats the rate of levee growth as a function of distance along the flow path. We show how this model can be used with a terrestrial flow and a long lava flow on Mars. The key statement of the new formulation is the rate of transfer from the active component to the levees (or other passive components) through an element dx along the path of the flow. This volumetric transfer equation is presented.

  1. Exciton formation as a rate limiting step for charge recombination in disordered organic molecules or polymers

    SciTech Connect

    Preezant, Yevgeni; Tessler, Nir

    2011-01-01

    The exciton formation (direct charge recombination) is studied and quantified as a function of material physical-properties such as the exciton binding energy, the exciton lifetime, and the mechanism causing the electronic disorder. By using a model that is an extension of a charge transport model [Y. Preezant and N. Tessler, Phys. Rev. B 74, 235202 (2006)] we are able to compare the direct exciton formation rate with the one predicted by the Langevin model. Using reasonable material parameters we find that in many cases the overall balance between free charge carrier and excitons is significantly affected by the exciton formation rate with its values being significantly low compared to the Langevin rate. We also find that in order to describe the complete recombination process it is important to introduce an intermediate state which we term exciton-precursor. This is in contrast to the common practice of using the Langevin model which embeds the assumption that the exciton formation rate is negligibly fast. The relations found between the physical-properties and the recombination rate can explain why certain materials exhibit Langevin rate while others exhibit significantly suppressed rates. This would eventually lead to the design of new materials better suited for either photocells or light-emitting diodes.

  2. Conditions for Circumstellar Disc Formation II: Effects of Initial Cloud Stability and Mass Accretion Rate

    NASA Astrophysics Data System (ADS)

    Machida, Masahiro N.; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro

    2016-09-01

    Disc formation in strongly magnetized cloud cores is investigated using a three-dimensional magnetohydrodynamic simulation with a focus on the effects of the initial cloud stability and the mass accretion rate. The initial cloud stability greatly alters the disc formation process even for prestellar clouds with the same mass-to-flux ratio. A high mass accretion rate onto the disc-forming region is realized in initially unstable clouds, and a large angular momentum is introduced into the circumstellar region in a short time. The region around the protostar has both a thin infalling envelope and a weak magnetic field, which both weaken the effect of magnetic braking. The growth of the rotation-supported disc is promoted in such unstable clouds. Conversely, clouds in an initially near-equilibrium state show lower accretion rates of mass and angular momentum. The angular momentum is transported to the outer envelope before protostar formation. After protostar formation, the circumstellar region has a thick infalling envelope and a strong magnetic field that effectively brake the disc. As a result, disc formation is suppressed when the initial cloud is in a nearly stable state. The density distribution of the initial cloud also affects the disc formation process. Disc growth strongly depends on the initial conditions when the prestellar cloud has a uniform density, whereas there is no significant difference in the disc formation process in prestellar clouds with nonuniform densities.

  3. Single-Molecule Kinetics Reveal Cation-Promoted DNA Duplex Formation Through Ordering of Single-Stranded Helices

    PubMed Central

    Dupuis, Nicholas F.; Holmstrom, Erik D.; Nesbitt, David J.

    2013-01-01

    In this work, the kinetics of short, fully complementary oligonucleotides are investigated at the single-molecule level. Constructs 6–9 bp in length exhibit single exponential kinetics over 2 orders of magnitude time for both forward (kon, association) and reverse (koff, dissociation) processes. Bimolecular rate constants for association are weakly sensitive to the number of basepairs in the duplex, with a 2.5-fold increase between 9 bp (k′on = 2.1(1) × 106 M−1 s−1) and 6 bp (k′on = 5.0(1) × 106 M−1 s−1) sequences. In sharp contrast, however, dissociation rate constants prove to be exponentially sensitive to sequence length, varying by nearly 600-fold over the same 9 bp (koff = 0.024 s−1) to 6 bp (koff = 14 s−1) range. The 8 bp sequence is explored in more detail, and the NaCl dependence of kon and koff is measured. Interestingly, konincreases by >40-fold (kon = 0.10(1) s−1 to 4.0(4) s−1 between [NaCl] = 25 mM and 1 M), whereas in contrast, koffdecreases by fourfold (0.72(3) s−1 to 0.17(7) s−1) over the same range of conditions. Thus, the equilibrium constant (Keq) increases by ≈160, largely due to changes in the association rate, kon. Finally, temperature-dependent measurements reveal that increased [NaCl] reduces the overall exothermicity (ΔΔH° > 0) of duplex formation, albeit by an amount smaller than the reduction in entropic penalty (−TΔΔS° < 0). This reduced entropic cost is attributed to a cation-facilitated preordering of the two single-stranded species, which lowers the association free-energy barrier and in turn accelerates the rate of duplex formation. PMID:23931323

  4. Structure of the DSM-IV personality disorders as revealed in clinician ratings.

    PubMed

    Blais, Mark A; Malone, Johanna C

    2013-05-01

    The revisions proposed for the DSM-5 would greatly alter how personality pathology is conceptualized, assessed, and diagnosed. One aspect of the proposed changes, elimination of four current personality disorders, has raised considerable controversy. The present study attempts to inform this debate by exploring clinicians' views of the structure of Personality Disorders using the current diagnostic system, the DSM-IV. An exploratory factor analysis was conducted on the DSM-IV Personality Disorder criteria using clinician ratings for 280 patients. The factor analysis revealed eight clear and meaningful factors. The eight factors contained all six personality disorders proposed for retention in DSM-5 but also contained clear representations of two disorders (Paranoid and Schizoid) identified for removal from the system. These conditions appear to have clinical utility and their removal may have unintended negative consequences in clinical practice. Dependent and Avoidant criteria also merged to form a new construct with interesting clinical implications. These findings provide new insights into the complex typologies clinicians employ when applying the DSM-IV system to personality disordered patients. Lastly we argue that successful refinement of clinically significant constructs, like diagnostic systems, requires a balanced appraisal of evidence for clinical utility as well as external and internal validity. PMID:23219361

  5. Bayesian coalescent inference reveals high evolutionary rates and diversification of Zika virus populations.

    PubMed

    Fajardo, Alvaro; Soñora, Martín; Moreno, Pilar; Moratorio, Gonzalo; Cristina, Juan

    2016-10-01

    Zika virus (ZIKV) is a member of the family Flaviviridae. In 2015, ZIKV triggered an epidemic in Brazil and spread across Latin America. By May of 2016, the World Health Organization warns over spread of ZIKV beyond this region. Detailed studies on the mode of evolution of ZIKV strains are extremely important for our understanding of the emergence and spread of ZIKV populations. In order to gain insight into these matters, a Bayesian coalescent Markov Chain Monte Carlo analysis of complete genome sequences of recently isolated ZIKV strains was performed. The results of these studies revealed a mean rate of evolution of 1.20 × 10(-3) nucleotide substitutions per site per year (s/s/y) for ZIKV strains enrolled in this study. Several variants isolated in China are grouped together with all strains isolated in Latin America. Another genetic group composed exclusively by Chinese strains were also observed, suggesting the co-circulation of different genetic lineages in China. These findings indicate a high level of diversification of ZIKV populations. Strains isolated from microcephaly cases do not share amino acid substitutions, suggesting that other factors besides viral genetic differences may play a role for the proposed pathogenesis caused by ZIKV infection. J. Med. Virol. 88:1672-1676, 2016. © 2016 Wiley Periodicals, Inc. PMID:27278855

  6. Lidar surveys reveal eruptive volumes and rates at Etna, 2007-2010

    NASA Astrophysics Data System (ADS)

    Behncke, Boris; Fornaciai, Alessandro; Neri, Marco; Favalli, Massimiliano; Ganci, Gaetana; Mazzarini, Francesco

    2016-05-01

    The quantification of eruptive activity represents one major challenge in volcanology. Digital comparison of lidar-based elevation models of Etna (Italy) was made to quantify the volumes of volcanics emitted in 2007-2010. During this period, Etna produced several summit paroxysms followed by a flank eruption. We integrated the total volume difference resulting from the subtraction of the 2007 and 2010 digital elevation models with volumes of eruptive products based on field and aerial surveys to attribute volumes with hitherto unrealized precision to poorly constrained eruptions. The total erupted volume of 2007-2010 is >86 × 106 m3, most (~74 × 106 m3) of which is made up by the lava flows of the 2008-2009 flank eruption. The survey also reveals the high lava volume (5.73 × 106 m3) and average eruption rate (~400 m3 s-1) of the 10 May 2008 paroxysm, whose flow front stopped 6.2 km from the vent, not far from the town of Zafferana Etnea.

  7. ENVIRONMENTAL DEPENDENCE OF THE STAR FORMATION RATE, SPECIFIC STAR FORMATION RATE, AND THE PRESENCE OF ACTIVE GALACTIC NUCLEI FOR HIGH STELLAR MASS AND LOW STELLAR MASS GALAXIES

    SciTech Connect

    Deng Xinfa; Song Jun; Chen Yiqing; Jiang Peng; Ding Yingping

    2012-07-10

    Using two volume-limited main galaxy samples of the Sloan Digital Sky Survey Data Release 8 (SDSS DR8), we explore the environmental dependence of the star formation rate (SFR), specific star formation rate (SSFR), and the presence of active galactic nuclei (AGNs) for high stellar mass (HSM) and low stellar mass (LSM) galaxies. It is found that the environmental dependence of the SFR and SSFR for luminous HSM galaxies and faint LSM ones remains very strong: galaxies in the lowest density regime preferentially have higher SFR and SSFR than galaxies in the densest regime, while the environmental dependence of the SFR and SSFR for luminous LSM galaxies is substantially reduced. Our result also shows that the fraction of AGNs in HSM galaxies decreases as a function of density, while the one in LSM galaxies depends very little on local density. In the faint LSM galaxy sample, the SFR and SSFR of galaxies strongly decrease with increasing density, but the fraction of AGNs depends very little on local density. Such a result can rule out that AGNs are fueled by the cold gas in the disk component of galaxies that is also driving the star formation of those galaxies.

  8. Geologically Controlled Isotope-Time Patterns Reveal Early Differentiation and Crust Formation Processes

    NASA Astrophysics Data System (ADS)

    Bennett, V. C.; Nutman, A. P.

    2014-12-01

    The mechanisms of continental crust production and evolution in the early Earth remain controversial, as are questions of the relative roles of early differentiation versus subsequent tectonic procssing in creating Earth's chemical signatures. Here we present geologic observations integrated with whole rock major, trace element and Sm-Nd isotopic signatures and combined with U-Pb and Lu-Hf isotopic compositions of zircon populations from the same rocks, from the most extensive early rock record comprising the 3.9 Ga to 3.6 Ga terranes of southwest Greenland. These data reveal repeated patterns of formation of juvenile TTG crust and associated mafic and ultramafic rocks in convergent margin settings followed by formation of more evolved granites [1]. Our new zircon Lu-Hf data from rare 3.6-3.7 Ga tonalites within the Itsaq Gneiss Complex, obtained from single component, non-migmatitic gneisses with simple zircon populations, limited within sample Hf isotopic variability and accurate U-Pb ages, now document extraction of juvenile tonalites from a near chondritic mantle source between 3.9 Ga and 3.6 Ga. The more evolved, granitic rocks in each area show slightly negative initial ɛHf in accord with crustal reworking of the older (3.8-3.9 Ga) gniesses. There is no evidence for Hadean material in the sources of the granitoids. The Hf isotope-time patterns are consistent with juvenile crust production from a mantle source that experienced only modest amounts of prior crustal extraction. They are distinct from those predicted by reprocessing of an enriched Hadean mafic crust, as has been proposed for this region [2] and for the source of the Hadean Jack Hills zircons [3]. The well-documented, time decreasing, positive 142Nd anomalies [e.g., 4] from these rocks are further evidence of crustal derivation from a convecting mantle source, rather than reworking of an enriched mafic lithosphere. The 143Nd isotopic -time patterns are more complex, reflecting the interplay

  9. 40 CFR Table I-5 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for MEMS Manufacturing I Table I-5...) and By-Product Formation Rates (Bijk) for MEMS Manufacturing ER13NO13.021...

  10. 40 CFR Table I-5 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for MEMS Manufacturing I Table I-5...) and By-Product Formation Rates (Bijk) for MEMS Manufacturing Process type factors Process gas i...

  11. An Estimation of the Star Formation Rate in the Perseus Complex

    NASA Astrophysics Data System (ADS)

    Mercimek, Seyma

    2016-07-01

    The detailed study of all sources are carried on, by comparing the number of existing cores and YSOs from observations with the prediction from column density PDFs. With this investigation, we found a relation between starless cores and protostars that cores may be considered progenitors of the next generation of protostars, assuming the rate of star formation in the recent past is similar to the rate in the near future. These are also new results which have not been investigated previously. In addition, we also calculate the mean density of each starless core and its corresponding free-fall time in order to estimate star formation rate in near future. Following that, we obtained star formation efficiency from the existing stellar cores which later was used to estimate average stellar mass from standard IMF. Finally, we estimate how many starless cores will turn into stars in the predicted free fall time and how many stars will form from calculated core mass.

  12. Reflectometry-Ellipsometry Reveals Thickness, Growth Rate, and Phase Composition in Oxidation of Copper.

    PubMed

    Diaz Leon, Juan J; Fryauf, David M; Cormia, Robert D; Zhang, Min-Xian Max; Samuels, Kathryn; Williams, R Stanley; Kobayashi, Nobuhiko P

    2016-08-31

    The oxidation of copper is a complicated process. Copper oxide develops two stable phases at room temperature and standard pressure (RTSP): cuprous oxide (Cu2O) and cupric oxide (CuO). Both phases have different optical and electrical characteristics that make them interesting for applications such as solar cells or resistive switching devices. For a given application, it is necessary to selectively control oxide thickness and cupric/cuprous oxide phase volume fraction. The thickness and composition of a copper oxide film growing on the surface of copper widely depend on the characteristics of as-deposited copper. In this Research Article, two samples, copper films prepared by two different deposition techniques, electron-beam evaporation and sputtering, were studied. As the core part of the study, the formation of the oxidized copper was analyzed routinely over a period of 253 days using spectroscopic polarized reflectometry-spectroscopic ellipsometry (RE). An effective medium approximation (EMA) model was used to fit the RE data. The RE measurements were complemented and validated by using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and X-ray diffraction (XRD). Our results show that the two samples oxidized under identical laboratory ambient conditions (RTSP, 87% average relative humidity) developed unique oxide films following an inverse-logarithmic growth rate with thickness and composition different from each other over time. Discussion is focused on the ability of RE to simultaneously extract thickness (i.e., growth rate) and composition of copper oxide films and on plausible physical mechanisms responsible for unique oxidation habits observed in the two copper samples. It appears that extended surface characteristics (i.e., surface roughness and grain boundaries) and preferential crystalline orientation of as-deposited polycrystalline copper films control the growth kinetics of the copper oxide film. Analysis based on a noncontact

  13. Fossilized iron bacteria reveal a pathway to the biological origin of banded iron formation.

    PubMed

    Chi Fru, Ernest; Ivarsson, Magnus; Kilias, Stephanos P; Bengtson, Stefan; Belivanova, Veneta; Marone, Federica; Fortin, Danielle; Broman, Curt; Stampanoni, Marco

    2013-01-01

    Debates on the formation of banded iron formations in ancient ferruginous oceans are dominated by a dichotomy between abiotic and biotic iron cycling. This is fuelled by difficulties in unravelling the exact processes involved in their formation. Here we provide fossil environmental evidence for anoxygenic photoferrotrophic deposition of analogue banded iron rocks in shallow marine waters associated with an Early Quaternary hydrothermal vent field on Milos Island, Greece. Trace metal, major and rare earth elemental compositions suggest that the deposited rocks closely resemble banded iron formations of Precambrian origin. Well-preserved microbial fossils in combination with chemical data imply that band formation was linked to periodic massive encrustation of anoxygenic phototrophic biofilms by iron oxyhydroxide alternating with abiotic silica precipitation. The data implicate cyclic anoxygenic photoferrotrophy and their fossilization mechanisms in the construction of microskeletal fabrics that result in the formation of characteristic banded iron formation bands of varying silica and iron oxide ratios. PMID:23784372

  14. Distinctive Genome Reduction Rates Revealed by Genomic Analyses of Two Coxiella-Like Endosymbionts in Ticks

    PubMed Central

    Gottlieb, Yuval; Lalzar, Itai; Klasson, Lisa

    2015-01-01

    Genome reduction is a hallmark of symbiotic genomes, and the rate and patterns of gene loss associated with this process have been investigated in several different symbiotic systems. However, in long-term host-associated coevolving symbiont clades, the genome size differences between strains are normally quite small and hence patterns of large-scale genome reduction can only be inferred from distant relatives. Here we present the complete genome of a Coxiella-like symbiont from Rhipicephalus turanicus ticks (CRt), and compare it with other genomes from the genus Coxiella in order to investigate the process of genome reduction in a genus consisting of intracellular host-associated bacteria with variable genome sizes. The 1.7-Mb CRt genome is larger than the genomes of most obligate mutualists but has a very low protein-coding content (48.5%) and an extremely high number of identifiable pseudogenes, indicating that it is currently undergoing genome reduction. Analysis of encoded functions suggests that CRt is an obligate tick mutualist, as indicated by the possible provisioning of the tick with biotin (B7), riboflavin (B2) and other cofactors, and by the loss of most genes involved in host cell interactions, such as secretion systems. Comparative analyses between CRt and the 2.5 times smaller genome of Coxiella from the lone star tick Amblyomma americanum (CLEAA) show that many of the same gene functions are lost and suggest that the large size difference might be due to a higher rate of genome evolution in CLEAA generated by the loss of the mismatch repair genes mutSL. Finally, sequence polymorphisms in the CRt population sampled from field collected ticks reveal up to one distinct strain variant per tick, and analyses of mutational patterns within the population suggest that selection might be acting on synonymous sites. The CRt genome is an extreme example of a symbiont genome caught in the act of genome reduction, and the comparison between CLEAA and CRt

  15. A coherent digital demodulator for multiple signal formats and widely varying data rates

    NASA Technical Reports Server (NTRS)

    Mcguffin, Bruce F.

    1989-01-01

    The Tracking and Data Relay Satellite System (TDRSS) uses four ground station demodulators for K-band signals with data rates from 1 kb/s to 300 Mb/s. The author discusses the feasibility of replacing these demodulators with a single digital demodulator that may be reconfigured by altering stored parameters to accommodate all signal formats and data rates. This implementation will reduce total ground station cost and facilitate automation of ground station operation. Analysis of system performance concentrates on the carrier tracking loop. Analytic and simulation results relate system performance to parameter values and signal format as data rate and power vary independently on the In-phase and quadrature channels. It is demonstrated that a single digital demodulator can support TDRSS-compatible signals at data rates conservatively extending from 1K symbols/s to 10M symbols/s, using off-the-shelf hardware with 6 or more bits of accuracy.

  16. The history of cosmic baryons: X-ray emission versus star formation rate

    NASA Astrophysics Data System (ADS)

    Menci, N.; Cavaliere, A.

    2000-01-01

    We relate the star formation from cold baryons condensing in virialized structures to the X-ray properties of the associated diffuse, hot baryonic component. Our computations use the standard `semi-analytic' models to include and connect three sectors of the complex astrophysics involved: first, the formation of dark matter haloes through accretion and merging, after the standard hierarchical clustering; secondly, the star formation governed, after the current `recipes', by radiative cooling and by feedback of the supernova energy into the hot baryonic component; thirdly, and novel, the hydrodynamics and thermodynamics of the hot phase, rendered with our Punctuated Equilibria model. So we relate the X-ray observables concerning the intracluster medium (namely, the luminosity-temperature relation, the luminosity functions, the source counts) to the thermal energy of the gas pre-heated and expelled by supernovae following star formation, and then accreted during the subsequent merging events. Our main results are as follows. At fluxes fainter than FX~10-15ergcm-2s-1 the X-ray counts of extended extragalactic sources (as well as the faint end of the luminosity function, their contribution to the soft X-ray background, and the LX-T correlation at the group scales) increase considerably if the star formation rate is high for z>1 as indicated by growing optical/infrared evidence. Specifically, the counts in the range 0.5-2keV are increased by factors ~4 when the the feedback is decreased and the star formation is enhanced as to yield a flat shape of the star formation rate for 2formation, and supernova feedback) at z>2, and a new way to advance the understanding of the galaxy formation.

  17. Formation rates, stability and reactivity of sulfuric acid - amine clusters predicted by computational chemistry

    NASA Astrophysics Data System (ADS)

    Kurtén, Theo; Ortega, Ismael; Kupiainen, Oona; Olenius, Tinja; Loukonen, Ville; Reiman, Heidi; McGrath, Matthew; Vehkamäki, Hanna

    2013-04-01

    Despite the importance of atmospheric particle formation for both climate and air quality, both experiments and non-empirical models using e.g. sulfuric acid, ammonia and water as condensing vapors have so far been unable to reproduce atmospheric observations using realistic trace gas concentrations. Recent experimental and theoretical evidence has shown that this mystery is likely resolved by amines. Combining first-principles evaporation rates for sulfuric acid - dimethylamine clusters with cluster kinetic modeling, we show that even sub-ppt concentrations of amines, together with atmospherically realistic concentrations of sulfuric acid, result in formation rates close to those observed in the atmosphere. Our simulated cluster formation rates are also close to, though somewhat larger than, those measured at the CLOUD experiment in CERN for both sulfuric acid - ammonia and sulfuric acid - dimethylamine systems. A sensitivity analysis indicates that the remaining discrepancy for the sulfuric acid - amine particle formation rates is likely caused by steric hindrances to cluster formation (due to alkyl groups of the amine molecules) rather than by significant errors in the evaporation rates. First-principles molecular dynamic and reaction kinetic modeling shed further light on the microscopic physics and chemistry of sulfuric acid - amine clusters. For example, while the number and type of hydrogen bonds in the clusters typically reach their equilibrium values on a picosecond timescale, and the overall bonding patterns predicted by traditional "static" quantum chemical calculations seem to be stable, the individual atoms participating in the hydrogen bonds continuously change at atmospherically realistic temperatures. From a chemical reactivity perspective, we have also discovered a surprising phenomenon: clustering with sulfuric acid molecules slightly increases the activation energy required for the abstraction of alkyl hydrogens from amine molecules. This implies

  18. Metasomatic Diamond Formation revealed by X-Ray CT Scanning of Diamondiferous Eclogites from Southern Africa

    NASA Astrophysics Data System (ADS)

    Richardson, S. H.; Kahle, R. L.; Shaw-Kahle, B.; Gurney, J. J.; du Plessis, A.

    2014-12-01

    In this study, a private collection of diamondiferous eclogite xenoliths has been made available for non-destructive investigation. All samples have at least one diamond visible. The samples are predominantly sourced from the Excelsior and Newlands mines (South Africa), with additional samples from Roberts Victor mine (South Africa) and Orapa (Botswana). 3D volume models of the samples were created using X-ray tomography. The 3D images reveal abundant secondary veining that is clearly younger than the eclogite. Diamonds are located in fluid pathways and occur in both altered garnet and altered clinopyroxene. Most of the veining is unrelated to the spatial positioning of diamond in the samples. In some instances, early veining has annealed or partially annealed, suggesting a range in timing of at least some of the several metasomatic events that have affected the rock. Importantly, in the most graphic examples, a clear distinction can be seen between diamond-bearing and non-diamond-bearing veins, even where sulphide is present in abundance in the non-diamond-bearing veins. The amount of diamond detected in the xenoliths varies from a single crystal to well over 50 diamonds forming more than 9% of the rock. This extreme value contrasts with the diamond recovery from currently viable diamond mines of less than 2ppm or 0.0002%. The morphology of the diamonds includes step-faced flat-faced octahedra, single crystals and aggregates. This is particularly a feature of diamonds in the Excelsior specimens. In the samples from Newlands and Orapa, in contrast, diamond surfaces reflect resorption processes such as rounding and corrosion of the diamonds. The following conclusions can be drawn from this study: Diamonds in this collection, sourced from within the Kalahari craton, appear to have formed by a metasomatic process during which fluids infiltrated pre-existing mantle-derived eclogite; Several metasomatic events have occurred during the residence of the eclogite in the

  19. Effects of Varying Response Formats on Self-Ratings of Life-Satisfaction

    ERIC Educational Resources Information Center

    Mazaheri, Mehrdad; Theuns, Peter

    2009-01-01

    A sample of 1,737 volunteering students, randomly assigned to 12 conditions, rated their current overall (dis)satisfaction with life. Each condition used 1 of 12 response formats, differing in (1) "polarity" ("bipolar" versus "unipolar"), (2) "orientation" ("horizontal" versus "vertical"), and (3) "anchoring" (-5 to +5, "Not Numbered," and 0 "to"…

  20. Revisiting the formation rate and redshift distribution of long gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Kanaan, C.; de Freitas Pacheco, J. A.

    2013-11-01

    Using a novel approach, the distribution of fluences of long gamma-ray bursts derived from the Swift-BAT catalog was reproduced by a jet-model characterized by the distribution of the total radiated energy in γ-rays and the distribution of the aperture angle of the emission cone. The best fit between simulated and observed fluence distributions permits one to estimate the parameters of the model. An evolution of the median energy of the bursts is required to adequately reproduce the observed redshift distribution of the events when the formation rate of γ-ray bursts follows the cosmic star formation rate. For our preferred model, the median jet energy evolves as EJ ∝ e0.5(1 + z) and the mean expected jet energy is 3.0 × 1049 erg, which agrees with the mean value derived from afterglow data. The estimated local formation rate is Rgrb = 290 Gpc-3 yr-1, representing less than 9% of the local formation rate of type Ibc supernovae. This result also suggests that the progenitors of long gamma-ray bursts have masses ≥ 90 M⊙ when a Miller-Scalo initial mass function is assumed.

  1. Circulating leptin is negatively associated with the isotopically-measured bone formation rate in pubertal adolescents

    Technology Transfer Automated Retrieval System (TEKTRAN)

    BACKGROUND: Animal studies show that serum leptin (SL) is associated with decreased bone formation (BF) and increased bone resorption (BR) rates via its effects on the sympathetic nervous system. Pediatric data on these relationships are limited due to lack of accurate methodology for in vivo assess...

  2. RECONCILING THE GAMMA-RAY BURST RATE AND STAR FORMATION HISTORIES

    SciTech Connect

    Jimenez, Raul; Piran, Tsvi E-mail: tsvi.piran@huji.ac.il

    2013-08-20

    While there are numerous indications that gamma-ray bursts (GRBs) arise from the deaths of massive stars, the GRB rate does not follow the global cosmic star formation rate and, within their hosts, GRBs are more concentrated in regions of very high star formation. We explain both puzzles here. Using the publicly available VESPA database of the Sloan Digital Sky Survey (SDSS) Data Release 7 spectra, we explore a multi-parameter space in galaxy properties such as stellar mass, metallicity, and dust to find the subset of galaxies that reproduces the GRB rate recently obtained by Wanderman and Piran. We find that only galaxies with present stellar masses below <10{sup 10} M{sub Sun} and low metallicity reproduce the observed GRB rate. This is consistent with direct observations of GRB hosts and provides an independent confirmation of the nature of GRB hosts. Because of the significantly larger sample of SDSS galaxies, we compute their correlation function and show that they are anti-biased with respect to dark matter: they are in filaments and voids. Using recent observations of massive stars in local dwarfs we show how the fact that GRB host galaxies are dwarfs can explain the observation that GRBs are more concentrated in regions of high star formation than are supernovae. Finally, we explain these results using new theoretical advances in the field of star formation.

  3. Impact of star formation history on the measurement of star formation rates: do we have to reassess the cosmic star formation rate?

    NASA Astrophysics Data System (ADS)

    Boquien, Médéric; Buat, Véronique; Perret, Valentin

    2015-08-01

    One of the key assumptions to measure the SFR of a galaxy is its SFH (star formation history). Most classical estimators are based on the assumption of a constant SFR over a period of 100 Myr. If this assumption seems reasonable at first sight for low redshift spiral galaxies evolving secularly, it is unlikely to hold true for interacting systems or at higher redshifts where the SFR necessarily varies on timescales that can be similar or shorter than 100 Myr.Even if in general we cannot uncover the SFH of galaxies in detail due to numerous degeneracies, it should nevertheless still be possible to investigate in isolation the impact of short- and long-term variations of the SFH on the measure of the SFR. To do so we have relied on the latest generation of high resolution hydrodynamical simulations of star-forming galaxies. Such simulations have now become so detailed that they provide us with realistic and reliable SFH. Combining these SFH with the CIGALE SED modelling code we have been able to simulate the observations of 23 main-sequence galaxies between redshift 1 and 2 and follow them every Myr over the course of several hundred Myr. Such an outstanding simulated dataset has allowed us to investigate the impact of realistic SFH on the measure of the SFR with classical methods.In this talk I will report that except for tracers related to the Lyman continuum (such as Hα for instance), classical SFR estimators calibrated over 100 Myr overestimate the true SFR from ~25% in the far-ultraviolet to ~65% in the U band. Such biases are due 1) to the contribution of stars living longer than 100 Myr, and 2) to variations of the SFR on timescales longer than a few tens of Myr. Rapid variations of the SFR increase the uncertainty on the determination of the instantaneous SFR, but have no long term effect. These discrepancies between the true and estimated SFR may explain in part the tension between the integral of the cosmic SFR density and the cosmic stellar mass density

  4. UNLEASHING POSITIVE FEEDBACK: LINKING THE RATES OF STAR FORMATION, SUPERMASSIVE BLACK HOLE ACCRETION, AND OUTFLOWS IN DISTANT GALAXIES

    SciTech Connect

    Silk, Joseph

    2013-08-01

    Pressure-regulated star formation is a simple variant on the usual supernova-regulated star formation efficiency that controls the global star formation rate as a function of cold gas content in star-forming galaxies, and accounts for the Schmidt-Kennicutt law in both nearby and distant galaxies. Inclusion of active galactic nucleus (AGN) induced pressure, by jets and/or winds that flow back onto a gas-rich disk, can lead, under some circumstances, to significantly enhanced star formation rates, especially at high redshift and most likely followed by the more widely accepted phase of star formation quenching. Simple expressions are derived that relate supermassive black hole growth, star formation, and outflow rates. The ratios of black hole to spheroid mass and of both black hole accretion and outflow rates to star formation rate are predicted as a function of time. I suggest various tests of the AGN-triggered star formation hypothesis.

  5. Temporal variability of transformation, formation, and subduction rates of upper Southern Ocean waters

    NASA Astrophysics Data System (ADS)

    Kwon, Eun Young

    2013-11-01

    Kinematic and thermodynamic approaches are employed to diagnose the time-dependent transformation, formation, and subduction rates of upper Southern Ocean waters in a multidecadal simulation within an eddy-permitting coupled climate model. In the Subantarctic Mode Water (SAMW) density class, a convergence of diapycnal volume fluxes leads to the formation and inflation of mixed layer waters during winter. A portion of this water is detrained into the pycnocline during early spring, when surface heating restratifies the deep winter mixed layer. The annually averaged subduction rate of SAMW shows pronounced interannual variability, partly controlled by the temporal tendency of the winter mixed layer depth from one year to the next. No significant correlation between the Southern Annular Mode (SAM) and the isopycnally integrated SAMW subduction rate is apparent. However, Ekman downwelling/upwelling intensities modulated by the SAM influence interannual variations in the subduction rates of water masses lighter and heavier than SAMW with an opposing sign: during positive phases of the SAM, more pycnocline waters are entrained into the mixed layer and transformed into lighter densities within the Antarctic Intermediate Water density class, whereas more mixed layer waters are subducted into the pycnocline within the Subtropical Mode Water density class. Such distinct responses of upper Southern Ocean water masses to the SAM are qualitatively consistent with observational constraints. Based on a comparison between offline kinematic and thermodynamic diagnostics, we infer that diapycnal mixing within the mixed layer may contribute up to 50% of the formation rate of SAMW on interannual timescales.

  6. Measurement of the Resonant dμt Molecular Formation Rate in Solid HD

    NASA Astrophysics Data System (ADS)

    Porcelli, T. A.; Adamczak, A.; Bailey, J. M.; Beer, G. A.; Douglas, J. L.; Faifman, M. P.; Fujiwara, M. C.; Huber, T. M.; Kammel, P.; Kim, S. K.; Knowles, P. E.; Kunselman, A. R.; Maier, M.; Markushin, V. E.; Marshall, G. M.; Mason, G. R.; Mulhauser, F.; Olin, A.; Petitjean, C.; Zmeskal, J.

    2001-04-01

    Measurements of muon-catalyzed dt fusion ( dμt-->4He+n+μ-) in solid HD have been performed. The theory describing the energy dependent resonant molecular formation rate for the reaction μt+HD-->[\\(dμt\\)pee]* is compared to experimental results in a pure solid HD target. Constraints on the rates are inferred through the use of a Monte Carlo model developed specifically for the experiment. From the time-of-flight analysis of fusion events in 16 and 37 μg˙cm-2 targets, an average formation rate consistent with 0.897+/-\\(0.046\\)stat+/-\\(0.166\\)syst times the theoretical prediction was obtained.

  7. Transformation-rate maxima during lath martensite formation: plastic vs. elastic shape strain accommodation

    NASA Astrophysics Data System (ADS)

    Loewy, Sarah; Rheingans, Bastian; Mittemeijer, Eric J.

    2016-05-01

    Recently, a modulated formation behaviour of lath martensite in Fe-Ni(-based) alloys was observed, exhibiting a series of transformation-rate maxima. This peculiar transformation behaviour was explained on the basis of the hierarchical microstructure of lath martensite, minimising the net shape strain associated with martensite formation, by a block-by-block formation of martensite packages occurring simultaneously in all packages. In the present work, the martensitic transformation upon slow cooling of two Fe-Ni alloys, containing 22 and 25 at.% of Ni, respectively, was investigated by high-resolution dilatometry with the aim of identifying the influence of alloy composition on the modulated transformation behaviour. The differences observed for the two alloys, a more rapid sequence of the transformation-rate maxima and a narrower temperature range in case of Fe-25 at.% Ni, can be explained consistently as a consequence of the lower transformation temperatures in Fe-25 at.% Ni, highlighting the role of temporary accommodation of the shape strain during formation of the lath martensite microstructure: the depression of the transformation toward lower temperatures leads to a higher strength of the austenite, hence resulting in a more elastic (less plastic) temporary accommodation of the shape strain upon block formation and thereby in a more effective mutual compensation of the shape strain by neighbouring blocks. A kinetic model on the basis of energy-change considerations is presented which is able to describe the observed modulated transformation behaviour.

  8. Analysis of Metmyoglobin Formation Rates in Frozen Tuna Meat during Frozen Storage

    NASA Astrophysics Data System (ADS)

    Viriyarattanasak, Chotika; Watanabe, Manabu; Suzuki, Toru

    Formation of metmyoglobin (metMb) in frozen tuna meat stored at -90, -60, -40, -30, -20, and -10°C for approximately 6 months was investigated. The reaction rate of metMB formation was estimated from a linear plot of ln ([M∞ . Mt] /[M∞ . Mo]) and storage time (t) for each storage temperature (Ts) (M∞, Mt, and Mo are metMb contents at times t = t∞, t, and 0, respectively). When M∞ was assumed to be 100%, the rate of metMb formation followed the first-order reaction only during the early stage of storage period. MetMb formation, however obeyed the first-order reaction for all test temperatures even during long-term storage when M∞ was assumed to be dependent on storage temperature (M∞(Ts)). A discontinuity was observed in the temperature dependence of M∞(Ts) at storage temperature range between -60 and -40°C, which was attributed to the glass transition of protein system. On the other hand, the temperature dependence of metMb formation did not show a significant change over all storage temperatures.

  9. Gas hydrate formation rates from dissolved-phase methane in porous laboratory specimens

    USGS Publications Warehouse

    Waite, William F.; Spangenberg, E.K.

    2013-01-01

    Marine sands highly saturated with gas hydrates are potential energy resources, likely forming from methane dissolved in pore water. Laboratory fabrication of gas hydrate-bearing sands formed from dissolved-phase methane usually requires 1–2 months to attain the high hydrate saturations characteristic of naturally occurring energy resource targets. A series of gas hydrate formation tests, in which methane-supersaturated water circulates through 100, 240, and 200,000 cm3 vessels containing glass beads or unconsolidated sand, show that the rate-limiting step is dissolving gaseous-phase methane into the circulating water to form methane-supersaturated fluid. This implies that laboratory and natural hydrate formation rates are primarily limited by methane availability. Developing effective techniques for dissolving gaseous methane into water will increase formation rates above our observed (1 ± 0.5) × 10−7 mol of methane consumed for hydrate formation per minute per cubic centimeter of pore space, which corresponds to a hydrate saturation increase of 2 ± 1% per day, regardless of specimen size.

  10. Time series analyses reveal environmental and fisheries controls on Atlantic horse mackerel (Trachurus trachurus) catch rates

    NASA Astrophysics Data System (ADS)

    Leitão, Francisco

    2015-12-01

    Time-series models (Dynamic factorial analyses and; Min/max autocorrelation factor analysis) were used to explore the relative influences of environmental variables and fishing pressure of trawl, seine and artisanal fleets on catch rates on Trachurus trachurus in ICES IXa sub-divisions (IXaCN-North coast; IXa- CS-South coast; IXaS-Algarve, South coast, Algarve). Fishing effort influenced catch rates in all areas with a 2 year lag and fishing pressure for each area was related to specific fleet sectors effort. In IXaCN, winter upwelling (spawning peak) and both summer northerly wind and wind magnitude (outside of the spawning peak) were strongly correlated with catch rates. In IXaCS summer/autumn westerly winds were related with catch rates. Northerly winds in spring, upwelling and SST (winter and autumn) were related with catch rates in IXaS-Algarve. For species with a long spawning season such as horse mackerel, seasonal analyses at broad regional scales can detract from a better understanding of variability in short term sub-stock catch rates. Favorable environmental conditions, even during seasons with low spawning activity can positively affect catch rates. Ignoring the role of regional oceanographic features on the spatial distribution of the sub-stocks when analysing variability in catch rates can lead to poor inferences about the productivity of the populations.

  11. Displacement damage rate dependence of defect cluster formation in α-Fe during irradiation

    NASA Astrophysics Data System (ADS)

    Watanabe, Y.; Morishita, K.; Yamamoto, Y.; Hamaguchi, D.; Tanigawa, H.

    2013-05-01

    Formation kinetics of defect clusters in pure iron during irradiation has been numerically investigated by reaction rate theory, with focusing on nucleation process of vacancy clusters (voids) and self-interstitial-atoms (SIA) clusters under a wide range of atomic displacement damage rate (dpa rate) and temperature conditions. In the rate theory model, the size dependence of thermal stability of a defect cluster is treated for a wide range of cluster size. The numerical analysis shows that the nucleation processes of voids and SIA-clusters are quite different from each other. As to the voids, the nucleation rate of voids depends much on temperature and dpa rate, and has the individual peak temperature for each dpa rate, during which the peak temperature increases with increasing dpa rate. This tendency for void nucleation is similar to that for void swelling observed in experiments. As to the SIA-clusters, the nucleation rate of SIA-clusters does not depend much on temperature and has no peak temperatures because of the relatively high thermal stability of an SIA-cluster, indicating that the conventional model (di-interstitial model) is applicable to describe the nucleation of SIA-clusters in a wide range of temperature.

  12. Crystal structure of listeriolysin O reveals molecular details of oligomerization and pore formation

    NASA Astrophysics Data System (ADS)

    Köster, Stefan; van Pee, Katharina; Hudel, Martina; Leustik, Martin; Rhinow, Daniel; Kühlbrandt, Werner; Chakraborty, Trinad; Yildiz, Özkan

    2014-04-01

    Listeriolysin O (LLO) is an essential virulence factor of Listeria monocytogenes that causes listeriosis. Listeria monocytogenes owes its ability to live within cells to the pH- and temperature-dependent pore-forming activity of LLO, which is unique among cholesterol-dependent cytolysins. LLO enables the bacteria to cross the phagosomal membrane and is also involved in activation of cellular processes, including the modulation of gene expression or intracellular Ca2+ oscillations. Neither the pore-forming mechanism nor the mechanisms triggering the signalling processes in the host cell are known in detail. Here, we report the crystal structure of LLO, in which we identified regions important for oligomerization and pore formation. Mutants were characterized by determining their haemolytic and Ca2+ uptake activity. We analysed the pore formation of LLO and its variants on erythrocyte ghosts by electron microscopy and show that pore formation requires precise interface interactions during toxin oligomerization on the membrane.

  13. Comparative genomics reveals convergent rates of evolution in ant-plant mutualisms.

    PubMed

    Rubin, Benjamin E R; Moreau, Corrie S

    2016-01-01

    Symbiosis-the close and often long-term interaction of species-is predicted to drive genome evolution in a variety of ways. For example, parasitic interactions have been shown to increase rates of molecular evolution, a trend generally attributed to the Red Queen Hypothesis. However, it is much less clear how mutualisms impact the genome, as both increased and reduced rates of change have been predicted. Here we sequence the genomes of seven species of ants, three that have convergently evolved obligate plant-ant mutualism and four closely related species of non-mutualists. Comparing these sequences, we investigate how genome evolution is shaped by mutualistic behaviour. We find that rates of molecular evolution are higher in the mutualists genome wide, a characteristic apparently not the result of demography. Our results suggest that the intimate relationships of obligate mutualists may lead to selective pressures similar to those seen in parasites, thereby increasing rates of evolution. PMID:27557866

  14. Comparative genomics reveals convergent rates of evolution in ant–plant mutualisms

    PubMed Central

    Rubin, Benjamin E. R.; Moreau, Corrie S.

    2016-01-01

    Symbiosis—the close and often long-term interaction of species—is predicted to drive genome evolution in a variety of ways. For example, parasitic interactions have been shown to increase rates of molecular evolution, a trend generally attributed to the Red Queen Hypothesis. However, it is much less clear how mutualisms impact the genome, as both increased and reduced rates of change have been predicted. Here we sequence the genomes of seven species of ants, three that have convergently evolved obligate plant–ant mutualism and four closely related species of non-mutualists. Comparing these sequences, we investigate how genome evolution is shaped by mutualistic behaviour. We find that rates of molecular evolution are higher in the mutualists genome wide, a characteristic apparently not the result of demography. Our results suggest that the intimate relationships of obligate mutualists may lead to selective pressures similar to those seen in parasites, thereby increasing rates of evolution. PMID:27557866

  15. Long-Term Data Reveal Rate and Risk Factors for Subsequent Surgeries Following Initial ACL Reconstruction

    MedlinePlus

    ... we have not known the rate and risk factors for subsequent knee surgery until now,” said senior author Kurt Spindler, M.D., of Vanderbilt University. In the Multicenter Orthopaedic Outcomes Network (MOON) study, ...

  16. Late Cenozoic Himalayan Erosion Rates Revealed by Cosmogenic Isotopes in Foreland Sediments, Northern India

    NASA Astrophysics Data System (ADS)

    Scherler, D.; Barnes, J. B.; Insel, N.; Densmore, A.

    2015-12-01

    Most surface processes that transport sediment are influenced by climate. For example, more rainfall enhances runoff and stream capacity, and colder temperatures expand glaciers at the expense of rivers. Late Cenozoic cooling and glacial cycles during the Quaternary should thus have affected erosion of the Earth's surface. But whether these changes were also associated with an overall increase of erosion rates is not clear. Here, we assess the erosional response of the fluvial-dominated Yamuna catchment in the Garhwal Himalaya, northern India, to late Cenozoic cooling and Quaternary climatic oscillations. Our approach is to measure cosmogenic radionuclide (10Be) concentrations in fluvial sediments (n = 14) eroded from uplifting foreland deposits and compare them with modelled concentrations for different paleo-erosion rate scenarios. This approach differs from previous ones that determine paleo-erosion rates from 10Be concentrations in distinct samples from stratigraphic sections, and avoids misinterpreting short-term fluctuations in 10Be concentrations that are unrelated to erosion rates. We tested this approach in the Mohand Range in northwest India, where Miocene to Quaternary deposits of the paleo-Yamuna River are actively uplifting, and where a robust kinematic model and published stratigraphic age constraints exist. Our model free parameters are the shortening rate across the Main Frontal Thrust (MFT) and the onset of shortening, within a known amount of total MFT slip (4-5 km). Preliminary results show that we can reproduce the measured 10Be concentrations best when Himalayan erosion rates were lower in the past than they are now, or have been increasing towards the present. Within uncertainties, the best-fit parameter combinations give shortening rates between 10 and 20 mm/yr, which is consistent with independent estimates from a nearby dated strath terrace and expected uplift rates based on channel steepness indices. Scenarios in which erosion rates are

  17. The effect of clouds on photolysis rates and ozone formation in the unpolluted troposphere

    NASA Technical Reports Server (NTRS)

    Thompson, A. M.

    1984-01-01

    The photochemistry of the lower atmosphere is sensitive to short- and long-term meteorological effects; accurate modeling therefore requires photolysis rates for trace gases which reflect this variability. As an example, the influence of clouds on the production of tropospheric ozone has been investigated, using a modification of Luther's two-stream radiation scheme to calculate cloud-perturbed photolysis rates in a one-dimensional photochemical transport model. In the unpolluted troposphere, where stratospheric inputs of odd nitrogen appear to represent the photochemical source of O3, strong cloud reflectance increases the concentration of NO in the upper troposphere, leading to greatly enhanced rates of ozone formation. Although the rate of these processes is too slow to verify by observation, the calculation is useful in distinguishing some features of the chemistry of regions of differing mean cloudiness.

  18. Relative rates of coke formation from hydrocarbons in steam cracking of naphtha: 3. Aromatic hydrocarbons

    SciTech Connect

    Kopinke, F. . Section of Remediation Research); Zimmermann, G. ); Reyniers, G.C.; Froment, G.F. )

    1993-11-01

    Relative rate constants of coke formation (k) from 18 aromatic hydrocarbons during steam cracking of naphtha at 810 C were determined by application of [sup 14]C-labeled compounds. Benzene is a poor coke precursor (k = 0.3), whereas polycyclic structures like acenaphthylene, anthracene, and chrysene have a high coking potential in the pyrolysis reactor (k = 4.5--6) as well as in the TLE section (k = 12--30). The relation between structure and coke formation rate of aromatic hydrocarbons can be interpreted on the basis of their reactivity in radical reactions. Constituents of the fuel fraction ([ge] C[sub 9]) derived from nonaromatic feed components are more efficient in the TLE fouling than those stemming from benzene derivatives.

  19. GAS REGULATION OF GALAXIES: THE EVOLUTION OF THE COSMIC SPECIFIC STAR FORMATION RATE, THE METALLICITY-MASS-STAR-FORMATION RATE RELATION, AND THE STELLAR CONTENT OF HALOS

    SciTech Connect

    Lilly, Simon J.; Carollo, C. Marcella; Pipino, Antonio; Peng Yingjie; Renzini, Alvio

    2013-08-01

    A very simple physical model of galaxies is one in which the formation of stars is instantaneously regulated by the mass of gas in a reservoir with mass loss scaling with the star-formation rate (SFR). This model links together three different aspects of the evolving galaxy population: (1) the cosmic time evolution of the specific star-formation rate (sSFR) relative to the growth of halos, (2) the gas-phase metallicities across the galaxy population and over cosmic time, and (3) the ratio of the stellar to dark matter mass of halos. The gas regulator is defined by the gas consumption timescale ({epsilon}{sup -1}) and the mass loading {lambda} of the wind outflow {lambda}{center_dot}SFR. The simplest regulator, in which {epsilon} and {lambda} are constant, sets the sSFR equal to exactly the specific accretion rate of the galaxy; more realistic situations lead to an sSFR that is perturbed from this precise relation. Because the gas consumption timescale is shorter than the timescale on which the system evolves, the metallicity Z is set primarily by the instantaneous operation of the regulator system rather than by the past history of the system. The metallicity of the gas reservoir depends on {epsilon}, {lambda}, and sSFR, and the regulator system therefore naturally produces a Z(m{sub star}, SFR) relation if {epsilon} and {lambda} depend on the stellar mass m{sub star}. Furthermore, this relation will be the same at all epochs unless the parameters {epsilon} and {lambda} themselves change with time. A so-called fundamental metallicity relation is naturally produced by these conditions. The overall mass-metallicity relation Z(m{sub star}) directly provides the fraction f{sub star}(m{sub star}) of incoming baryons that are being transformed into stars. The observed Z(m{sub star}) relation of Sloan Digital Sky Survey (SDSS) galaxies implies a strong dependence of stellar mass on halo mass that reconciles the different faint-end slopes of the stellar and halo mass

  20. Elevated rates of gold mining in the Amazon revealed through high-resolution monitoring.

    PubMed

    Asner, Gregory P; Llactayo, William; Tupayachi, Raul; Luna, Ernesto Ráez

    2013-11-12

    Gold mining has rapidly increased in western Amazonia, but the rates and ecological impacts of mining remain poorly known and potentially underestimated. We combined field surveys, airborne mapping, and high-resolution satellite imaging to assess road- and river-based gold mining in the Madre de Dios region of the Peruvian Amazon from 1999 to 2012. In this period, the geographic extent of gold mining increased 400%. The average annual rate of forest loss as a result of gold mining tripled in 2008 following the global economic recession, closely associated with increased gold prices. Small clandestine operations now comprise more than half of all gold mining activities throughout the region. These rates of gold mining are far higher than previous estimates that were based on traditional satellite mapping techniques. Our results prove that gold mining is growing more rapidly than previously thought, and that high-resolution monitoring approaches are required to accurately quantify human impacts on tropical forests. PMID:24167281

  1. Elevated rates of gold mining in the Amazon revealed through high-resolution monitoring

    PubMed Central

    Asner, Gregory P.; Llactayo, William; Tupayachi, Raul; Luna, Ernesto Ráez

    2013-01-01

    Gold mining has rapidly increased in western Amazonia, but the rates and ecological impacts of mining remain poorly known and potentially underestimated. We combined field surveys, airborne mapping, and high-resolution satellite imaging to assess road- and river-based gold mining in the Madre de Dios region of the Peruvian Amazon from 1999 to 2012. In this period, the geographic extent of gold mining increased 400%. The average annual rate of forest loss as a result of gold mining tripled in 2008 following the global economic recession, closely associated with increased gold prices. Small clandestine operations now comprise more than half of all gold mining activities throughout the region. These rates of gold mining are far higher than previous estimates that were based on traditional satellite mapping techniques. Our results prove that gold mining is growing more rapidly than previously thought, and that high-resolution monitoring approaches are required to accurately quantify human impacts on tropical forests. PMID:24167281

  2. Surface Brightness Profiles and Star Formation Rates of Galaxies in NRGb054

    NASA Astrophysics Data System (ADS)

    Hansen, Ellen; Koopmann, Rebecca A.; Miller, Brendan; Durbala, Adriana; Fitzgerald, Garrett

    2016-01-01

    We present new optical R and H-alpha images of the galaxy group NRGb054, obtained with the WIYN 0.9m telescope at KPNO using the MOSAIC camera. This group was studied as part of the larger Undergraduate ALFALFA Team project investigating the effects of a group environment on star formation. The stacked H-alpha image was continuum subtracted by the removal of a scaled and stacked R image. Surface photometry was performed on R and continuum-subtracted H-alpha cutouts of 20 covered galaxies to determine the surface brightness as a function of radius. Integrating the continuum-subtracted H-alpha surface brightness profile provides the total star formation within that galaxy, while the shape of the profile illustrates how star formation is spread throughout the galaxy. We provide a catalog of surface brightness profiles and integrated star formation rates for NRGb054. We consider star formation as a function of galaxy-galaxy separation and galaxy location within the group, and discuss our findings in the context of the wider study. This work has been supported by NSF grant AST-1211005.

  3. OH{sup +} in astrophysical media: state-to-state formation rates, Einstein coefficients and inelastic collision rates with He

    SciTech Connect

    Gómez-Carrasco, Susana; Godard, Benjamin; Lique, François; Bulut, Niyazi; Kłos, Jacek; Roncero, Octavio; Aguado, Alfredo; Aoiz, F. Javier; Castillo, Jesús F.; Goicoechea, Javier R.; Etxaluze, Mireya; Cernicharo, José

    2014-10-10

    The rate constants required to model the OH{sup +} observations in different regions of the interstellar medium have been determined using state of the art quantum methods. First, state-to-state rate constants for the H{sub 2}(v = 0, J = 0, 1) + O{sup +}({sup 4} S) → H + OH{sup +}(X {sup 3}Σ{sup –}, v', N) reaction have been obtained using a quantum wave packet method. The calculations have been compared with time-independent results to assess the accuracy of reaction probabilities at collision energies of about 1 meV. The good agreement between the simulations and the existing experimental cross sections in the 0.01-1 eV energy range shows the quality of the results. The calculated state-to-state rate constants have been fitted to an analytical form. Second, the Einstein coefficients of OH{sup +} have been obtained for all astronomically significant rovibrational bands involving the X {sup 3}Σ{sup –} and/or A {sup 3}Π electronic states. For this purpose, the potential energy curves and electric dipole transition moments for seven electronic states of OH{sup +} are calculated with ab initio methods at the highest level, including spin-orbit terms, and the rovibrational levels have been calculated including the empirical spin-rotation and spin-spin terms. Third, the state-to-state rate constants for inelastic collisions between He and OH{sup +}(X {sup 3}Σ{sup –}) have been calculated using a time-independent close coupling method on a new potential energy surface. All these rates have been implemented in detailed chemical and radiative transfer models. Applications of these models to various astronomical sources show that inelastic collisions dominate the excitation of the rotational levels of OH{sup +}. In the models considered, the excitation resulting from the chemical formation of OH{sup +} increases the line fluxes by about 10% or less depending on the density of the gas.

  4. Submerged Conidiation and Product Formation by Aspergillus niger at Low Specific Growth Rates Are Affected in Aerial Developmental Mutants ▿

    PubMed Central

    Jørgensen, Thomas R.; Nielsen, Kristian F.; Arentshorst, Mark; Park, JooHae; van den Hondel, Cees A.; Frisvad, Jens C.; Ram, Arthur F.

    2011-01-01

    Exposure to an aerial environment or severe nutrient limitation induces asexual differentiation in filamentous fungi. Submerged cultivation of Aspergillus niger in carbon- and energy-limited retentostat cultures both induces and fuels conidiation. Physiological and transcriptomic analyses have revealed that this differentiation strongly affects product formation. Since conidiation is inherent in the aerial environment, we hypothesized that product formation near zero growth can be influenced by affecting differentiation or development of aerial hyphae in general. To investigate this idea, three developmental mutants (ΔfwnA, scl-1, and scl-2 mutants) that have no apparent vegetative growth defects were cultured in maltose-limited retentostat cultures. The secondary-metabolite profile of the wild-type strain defined flavasperone, aurasperone B, tensidol B, and two so far uncharacterized compounds as associated with conidium formation, while fumonisins B2, B4, and B6 were characteristic of early response to nutrient limitation by the vegetative mycelium. The developmental mutants responded differently to the severe substrate limitation, which resulted in distinct profiles of growth and product formation. fwnA encodes the polyketide synthase responsible for melanin biosynthesis during aerial differentiation, and we show that conidial melanin synthesis in submerged retentostat cultures and aurasperone B production are fwnA dependent. The scl-1 and scl-2 strains are two UV mutants generated in the ΔfwnA background that displayed reduced asexual conidiation and formed sclerotium-like structures on agar plates. The reduced conidiation phenotypes of the scl-1 and scl-2 strains are reflected in the retentostat cultivation and are accompanied by elimination or severely reduced accumulation of secondary metabolites and distinctly enhanced accumulation of extracellular protein. This investigation shows that submerged conidiation and product formation of a mitosporic fungus

  5. The rate and latency of star formation in dense, massive clumps in the Milky Way

    NASA Astrophysics Data System (ADS)

    Heyer, M.; Gutermuth, R.; Urquhart, J. S.; Csengeri, T.; Wienen, M.; Leurini, S.; Menten, K.; Wyrowski, F.

    2016-04-01

    Context. Newborn stars form within the localized, high density regions of molecular clouds. The sequence and rate at which stars form in dense clumps and the dependence on local and global environments are key factors in developing descriptions of stellar production in galaxies. Aims: We seek to observationally constrain the rate and latency of star formation in dense massive clumps that are distributed throughout the Galaxy and to compare these results to proposed prescriptions for stellar production. Methods: A sample of 24 μm-based Class I protostars are linked to dust clumps that are embedded within molecular clouds selected from the APEX Telescope Large Area Survey of the Galaxy. We determine the fraction of star-forming clumps, f∗, that imposes a constraint on the latency of star formation in units of a clump's lifetime. Protostellar masses are estimated from models of circumstellar environments of young stellar objects from which star formation rates are derived. Physical properties of the clumps are calculated from 870 μm dust continuum emission and NH3 line emission. Results: Linear correlations are identified between the star formation rate surface density, ΣSFR, and the quantities ΣH2/τff and ΣH2/τcross, suggesting that star formation is regulated at the local scales of molecular clouds. The measured fraction of star forming clumps is 23%. Accounting for star formation within clumps that are excluded from our sample due to 24 μm saturation, this fraction can be as high as 31%, which is similar to previous results. Dense, massive clumps form primarily low mass (<1-2 M⊙) stars with emergent 24 μm fluxes below our sensitivity limit or are incapable of forming any stars for the initial 70% of their lifetimes. The low fraction of star forming clumps in the Galactic center relative to those located in the disk of the Milky Way is verified. Full Tables 2-4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130

  6. Direct observation of mineral–organic composite formation reveals occlusion mechanism

    PubMed Central

    Rae Cho, Kang; Kim, Yi-Yeoun; Yang, Pengcheng; Cai, Wei; Pan, Haihua; Kulak, Alexander N.; Lau, Jolene L.; Kulshreshtha, Prashant; Armes, Steven P.; Meldrum, Fiona C.; De Yoreo, James J.

    2016-01-01

    Manipulation of inorganic materials with organic macromolecules enables organisms to create biominerals such as bones and seashells, where occlusion of biomacromolecules within individual crystals generates superior mechanical properties. Current understanding of this process largely comes from studying the entrapment of micron-size particles in cooling melts. Here, by investigating micelle incorporation in calcite with atomic force microscopy and micromechanical simulations, we show that different mechanisms govern nanoscale occlusion. By simultaneously visualizing the micelles and propagating step edges, we demonstrate that the micelles experience significant compression during occlusion, which is accompanied by cavity formation. This generates local lattice strain, leading to enhanced mechanical properties. These results give new insight into the formation of occlusions in natural and synthetic crystals, and will facilitate the synthesis of multifunctional nanocomposite crystals. PMID:26732046

  7. Direct observation of mineral–organic composite formation reveals occlusion mechanism

    DOE PAGESBeta

    Cho, Kang Rae; Kim, Yi -Yeoun; Yang, Pengcheng; Cai, Wei; Pan, Haihua; Kulak, Alexander N.; Lau, Jolene L.; Kulshreshtha, Prashant; Armes, Steven P.; Meldrum, Fiona C.; et al

    2016-01-06

    Manipulation of inorganic materials with organic macromolecules enables organisms to create biominerals such as bones and seashells, where occlusion of biomacromolecules within individual crystals generates superior mechanical properties. Current understanding of this process largely comes from studying the entrapment of micron-size particles in cooling melts. Here, by investigating micelle incorporation in calcite with atomic force microscopy and micromechanical simulations, we show that different mechanisms govern nanoscale occlusion. By simultaneously visualizing the micelles and propagating step edges, we demonstrate that the micelles experience significant compression during occlusion, which is accompanied by cavity formation. This generates local lattice strain, leading to enhancedmore » mechanical properties. Furthermore, these results give new insight into the formation of occlusions in natural and synthetic crystals, and will facilitate the synthesis of multifunctional nanocomposite crystals.« less

  8. Schottky barrier formation and band bending revealed by first- principles calculations

    PubMed Central

    Jiao, Yang; Hellman, Anders; Fang, Yurui; Gao, Shiwu; Käll, Mikael

    2015-01-01

    The formation of a Schottky barrier at the metal-semiconductor interface is widely utilised in semiconductor devices. With the emerging of novel Schottky barrier based nanoelectronics, a further microscopic understanding of this interface is in high demand. Here we provide an atomistic insight into potential barrier formation and band bending by ab initio simulations and model analysis of a prototype Schottky diode, i.e., niobium doped rutile titania in contact with gold (Au/Nb:TiO2). The local Schottky barrier height is found to vary between 0 and 1.26 eV depending on the position of the dopant. The band bending is caused by a dopant induced dipole field between the interface and the dopant site, whereas the pristine Au/TiO2 interface does not show any band bending. These findings open the possibility for atomic scale optimisation of the Schottky barrier and light harvesting in metal-semiconductor nanostructures. PMID:26065401

  9. Schottky barrier formation and band bending revealed by first- principles calculations

    NASA Astrophysics Data System (ADS)

    Jiao, Yang; Hellman, Anders; Fang, Yurui; Gao, Shiwu; Käll, Mikael

    2015-06-01

    The formation of a Schottky barrier at the metal-semiconductor interface is widely utilised in semiconductor devices. With the emerging of novel Schottky barrier based nanoelectronics, a further microscopic understanding of this interface is in high demand. Here we provide an atomistic insight into potential barrier formation and band bending by ab initio simulations and model analysis of a prototype Schottky diode, i.e., niobium doped rutile titania in contact with gold (Au/Nb:TiO2). The local Schottky barrier height is found to vary between 0 and 1.26 eV depending on the position of the dopant. The band bending is caused by a dopant induced dipole field between the interface and the dopant site, whereas the pristine Au/TiO2 interface does not show any band bending. These findings open the possibility for atomic scale optimisation of the Schottky barrier and light harvesting in metal-semiconductor nanostructures.

  10. Schottky barrier formation and band bending revealed by first- principles calculations.

    PubMed

    Jiao, Yang; Hellman, Anders; Fang, Yurui; Gao, Shiwu; Käll, Mikael

    2015-01-01

    The formation of a Schottky barrier at the metal-semiconductor interface is widely utilised in semiconductor devices. With the emerging of novel Schottky barrier based nanoelectronics, a further microscopic understanding of this interface is in high demand. Here we provide an atomistic insight into potential barrier formation and band bending by ab initio simulations and model analysis of a prototype Schottky diode, i.e., niobium doped rutile titania in contact with gold (Au/Nb:TiO2). The local Schottky barrier height is found to vary between 0 and 1.26 eV depending on the position of the dopant. The band bending is caused by a dopant induced dipole field between the interface and the dopant site, whereas the pristine Au/TiO2 interface does not show any band bending. These findings open the possibility for atomic scale optimisation of the Schottky barrier and light harvesting in metal-semiconductor nanostructures. PMID:26065401

  11. Direct observation of mineral-organic composite formation reveals occlusion mechanism

    NASA Astrophysics Data System (ADS)

    Rae Cho, Kang; Kim, Yi-Yeoun; Yang, Pengcheng; Cai, Wei; Pan, Haihua; Kulak, Alexander N.; Lau, Jolene L.; Kulshreshtha, Prashant; Armes, Steven P.; Meldrum, Fiona C.; de Yoreo, James J.

    2016-01-01

    Manipulation of inorganic materials with organic macromolecules enables organisms to create biominerals such as bones and seashells, where occlusion of biomacromolecules within individual crystals generates superior mechanical properties. Current understanding of this process largely comes from studying the entrapment of micron-size particles in cooling melts. Here, by investigating micelle incorporation in calcite with atomic force microscopy and micromechanical simulations, we show that different mechanisms govern nanoscale occlusion. By simultaneously visualizing the micelles and propagating step edges, we demonstrate that the micelles experience significant compression during occlusion, which is accompanied by cavity formation. This generates local lattice strain, leading to enhanced mechanical properties. These results give new insight into the formation of occlusions in natural and synthetic crystals, and will facilitate the synthesis of multifunctional nanocomposite crystals.

  12. Direct observation of mineral-organic composite formation reveals occlusion mechanism.

    PubMed

    Rae Cho, Kang; Kim, Yi-Yeoun; Yang, Pengcheng; Cai, Wei; Pan, Haihua; Kulak, Alexander N; Lau, Jolene L; Kulshreshtha, Prashant; Armes, Steven P; Meldrum, Fiona C; De Yoreo, James J

    2016-01-01

    Manipulation of inorganic materials with organic macromolecules enables organisms to create biominerals such as bones and seashells, where occlusion of biomacromolecules within individual crystals generates superior mechanical properties. Current understanding of this process largely comes from studying the entrapment of micron-size particles in cooling melts. Here, by investigating micelle incorporation in calcite with atomic force microscopy and micromechanical simulations, we show that different mechanisms govern nanoscale occlusion. By simultaneously visualizing the micelles and propagating step edges, we demonstrate that the micelles experience significant compression during occlusion, which is accompanied by cavity formation. This generates local lattice strain, leading to enhanced mechanical properties. These results give new insight into the formation of occlusions in natural and synthetic crystals, and will facilitate the synthesis of multifunctional nanocomposite crystals. PMID:26732046

  13. [Effect of aerobic training on cardiac autonomic regulation revealed by heart rate variability analysis].

    PubMed

    Zhang, L; Wang, S; Zhang, Z; Zheng, J; Wang, X

    1997-11-01

    The aim of the present work is to elucidate the effect of aerobiac training on cardic autonomic function and to clarify whether there is any association between the changes in cardiac regulation and the heart rate dynamics and orthostatic tolerance during LBNP testing. To achieve this, the heart rate variability (HRV) signals obtained from a group of eight students before and after a 6-mon aerobic training, as well as from six athletes (medium- and long distance runners) were analyzed by conventional spectral, dynamic spectral and non-linear analysis. Our results showed that the conventional AR spectral analysis could not provide data with significance, owing to its greater variance and inherent limitation in being able to reflect only the average statistical characters over a certain period. While from the data obtained by use of the time-varying AR spectral analysis we could follow the time course of cardiac vagal withdrawl and sympathetic excitation during LBNP exposure. Regarding the non linear methods used, beta estimates didn't provide any significant result, but the ApEn analysis of the HRV signal could detect subtle changes in heart rate dynamics associated with aerobic training. Moreover, after aerobic training, the increments delta ApEn and delta DNP during LB NP testing were closely correlated. Our results would have important implications for further work in elucidating the effect of aerobic training on heart rate dynamics and improving the work on HRV signal analysis. PMID:10322949

  14. Application of coalescent methods to reveal fine-scale rate variation and recombination hotspots.

    PubMed Central

    Fearnhead, Paul; Harding, Rosalind M; Schneider, Julie A; Myers, Simon; Donnelly, Peter

    2004-01-01

    There has been considerable recent interest in understanding the way in which recombination rates vary over small physical distances, and the extent of recombination hotspots, in various genomes. Here we adapt, apply, and assess the power of recently developed coalescent-based approaches to estimating recombination rates from sequence polymorphism data. We apply full-likelihood estimation to study rate variation in and around a well-characterized recombination hotspot in humans, in the beta-globin gene cluster, and show that it provides similar estimates, consistent with those from sperm studies, from two populations deliberately chosen to have different demographic and selectional histories. We also demonstrate how approximate-likelihood methods can be used to detect local recombination hotspots from genomic-scale SNP data. In a simulation study based on 80 100-kb regions, these methods detect 43 out of 60 hotspots (ranging from 1 to 2 kb in size), with only two false positives out of 2000 subregions that were tested for the presence of a hotspot. Our study suggests that new computational tools for sophisticated analysis of population diversity data are valuable for hotspot detection and fine-scale mapping of local recombination rates. PMID:15342541

  15. Effects of Antimicrobial Peptide Revealed by Simulations: Translocation, Pore Formation, Membrane Corrugation and Euler Buckling

    PubMed Central

    Chen, Licui; Jia, Nana; Gao, Lianghui; Fang, Weihai; Golubovic, Leonardo

    2013-01-01

    We explore the effects of the peripheral and transmembrane antimicrobial peptides on the lipid bilayer membrane by using the coarse grained Dissipative Particle Dynamics simulations. We study peptide/lipid membrane complexes by considering peptides with various structure, hydrophobicity and peptide/lipid interaction strength. The role of lipid/water interaction is also discussed. We discuss a rich variety of membrane morphological changes induced by peptides, such as pore formation, membrane corrugation and Euler buckling. PMID:23579956

  16. A novel cell-free system reveals a mechanism of circular DNA formation from tandem repeats.

    PubMed

    Cohen, S; Mechali, M

    2001-06-15

    One characteristic of genomic plasticity is the presence of extrachromosomal circular DNA (eccDNA). High levels of eccDNA are associated with genomic instability, exposure to carcinogens and aging. We have recently reported developmentally regulated formation of eccDNA that occurs preferentially in pre-blastula Xenopus laevis embryos. Multimers of tandemly repeated sequences were over-represented in the circle population while dispersed sequences were not detected, indicating that circles were not formed at random from any chromosomal sequence. Here we present detailed mechanistic studies of eccDNA formation in a cell-free system derived from Xenopus egg extracts. We show that naked chromosomal DNA from sperm or somatic tissues serves as a substrate for direct tandem repeat circle formation. Moreover, a recombinant bacterial tandem repeat can generate eccDNA in the extract through a de novo mechanism which is independent of DNA replication. These data suggest that the presence of a high level of any direct tandem repeat can confer on DNA the ability to be converted into circular multimers in the early embryo irrespective of its sequence and that homologous recombination is involved in this process. PMID:11410662

  17. 40 CFR Table I-7 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Electronics Manufacturing Pt. 98, Subpt. I, Table I-7 Table I-7 to Subpart I of Part 98—Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By... Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for PV Manufacturing I Table I-7...

  18. 40 CFR Table I-6 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Electronics Manufacturing Pt. 98, Subpt. I, Table I-6 Table I-6 to Subpart I of Part 98—Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By... Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for LCD Manufacturing I Table I-6...

  19. 40 CFR Table I-6 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Electronics Manufacturing Pt. 98, Subpt. I, Table I-6 Table I-6 to Subpart I of Part 98—Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By... Gas Utilization Rates (Uij) and By-Product Formation Rates(Bijk) for LCD Manufacturing I Table I-6...

  20. 40 CFR Table I-7 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Electronics Manufacturing Pt. 98, Subpt. I, Table I-7 Table I-7 to Subpart I of Part 98—Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By... Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for PV Manufacturing I Table I-7...

  1. Correlation Between Decay Rate and Amplitude of Solar Cycles as Revealed from Observations and Dynamo Theory

    NASA Astrophysics Data System (ADS)

    Hazra, Gopal; Karak, Bidya Binay; Banerjee, Dipankar; Choudhuri, Arnab Rai

    2015-06-01

    Using different proxies of solar activity, we have studied the following features of the solar cycle: i) The linear correlation between the amplitude of cycle and its decay rate, ii) the linear correlation between the amplitude of cycle and the decay rate of cycle , and iii) the anti-correlation between the amplitude of cycle and the period of cycle . Features ii) and iii) are very useful because they provide precursors for future cycles. We have reproduced these features using a flux-transport dynamo model with stochastic fluctuations in the Babcock-Leighton effect and in the meridional circulation. Only when we introduce fluctuations in meridional circulation, are we able to reproduce different observed features of the solar cycle. We discuss the possible reasons for these correlations.

  2. National Lupus Hospitalization Trends Reveal Rising Rates of Herpes Zoster and Declines in Pneumocystis Pneumonia

    PubMed Central

    Murray, Sara G.; Schmajuk, Gabriela; Trupin, Laura; Gensler, Lianne; Katz, Patricia P.; Yelin, Edward H.; Gansky, Stuart A.; Yazdany, Jinoos

    2016-01-01

    Objective Infection is a leading cause of morbidity and mortality in systemic lupus erythematosus (SLE). Therapeutic practices have evolved over the past 15 years, but effects on infectious complications of SLE are unknown. We evaluated trends in hospitalizations for severe and opportunistic infections in a population-based SLE study. Methods Data derive from the 2000 to 2011 United States National Inpatient Sample, including individuals who met a validated administrative definition of SLE. Primary outcomes were diagnoses of bacteremia, pneumonia, opportunistic fungal infection, herpes zoster, cytomegalovirus, or pneumocystis pneumonia (PCP). We used Poisson regression to determine whether infection rates were changing in SLE hospitalizations and used predictive marginals to generate annual adjusted rates of specific infections. Results We identified 361,337 SLE hospitalizations from 2000 to 2011 meeting study inclusion criteria. Compared to non-SLE hospitalizations, SLE patients were younger (51 vs. 62 years), predominantly female (89% vs. 54%), and more likely to be racial/ethnic minorities. SLE diagnosis was significantly associated with all measured severe and opportunistic infections. From 2000 to 2011, adjusted SLE hospitalization rates for herpes zoster increased more than non-SLE rates: 54 to 79 per 10,000 SLE hospitalizations compared with 24 to 29 per 10,000 non-SLE hospitalizations. Conversely, SLE hospitalizations for PCP disproportionately decreased: 5.1 to 2.5 per 10,000 SLE hospitalizations compared with 0.9 to 1.3 per 10,000 non-SLE hospitalizations. Conclusions Among patients with SLE, herpes zoster hospitalizations are rising while PCP hospitalizations are declining. These trends likely reflect evolving SLE treatment strategies. Further research is needed to identify patients at greatest risk for infectious complications. PMID:26731012

  3. Impacts of warming revealed by linking resource growth rates with consumer functional responses.

    PubMed

    West, Derek C; Post, David M

    2016-05-01

    Warming global temperatures are driving changes in species distributions, growth and timing, but much uncertainty remains regarding how climate change will alter species interactions. Consumer-Resource interactions in particular can be strongly impacted by changes to the relative performance of interacting species. While consumers generally gain an advantage over their resources with increasing temperatures, nonlinearities can change this relation near temperature extremes. We use an experimental approach to determine how temperature changes between 5 and 30 °C will alter the growth of the algae Scenedesmus obliquus and the functional responses of the small-bodied Daphnia ambigua and the larger Daphnia pulicaria. The impact of warming generally followed expectations, making both Daphnia species more effective grazers, with the increase in feeding rates outpacing the increases in algal growth rate. At the extremes of our temperature range, however, warming resulted in a decrease in Daphnia grazing effectiveness. Between 25 and 30 °C, both species of Daphnia experienced a precipitous drop in feeding rates, while algal growth rates remained high, increasing the likelihood of algal blooms in warming summer temperatures. Daphnia pulicaria performed significantly better at cold temperatures than D. ambigua, but by 20 °C, there was no significant difference between the two species, and at 25 °C, D. ambigua outperformed D. pulicaria. Warming summer temperatures will favour the smaller D. ambigua, but only over a narrow temperature range, and warming beyond 25 °C could open D. ambigua to invasion from tropical species. By fitting our results to temperature-dependent functions, we develop a temperature- and density-dependent model, which produces a metric of grazing effectiveness, quantifying the grazer density necessary to halt algal growth. This approach should prove useful for tracking the transient dynamics of other density-dependent consumer

  4. Strain-rate Dependence of Elastic Modulus Reveals Silver Nanoparticle Induced Cytotoxicity

    PubMed Central

    Caporizzo, Matthew Alexander; Roco, Charles M.; Ferrer, Maria Carme Coll; Grady, Martha E.; Parrish, Emmabeth; Eckmann, David M.; Composto, Russell John

    2015-01-01

    Force-displacement measurements are taken at different rates with an atomic force microscope to assess the correlation between cell health and cell viscoelasticity in THP-1 cells that have been treated with a novel drug carrier. A variable indentation-rate viscoelastic analysis, VIVA, is employed to identify the relaxation time of the cells that are known to exhibit a frequency dependent stiffness. The VIVA agrees with a fluorescent viability assay. This indicates that dextran-lysozyme drug carriers are biocompatible and deliver concentrated toxic material (rhodamine or silver nanoparticles) to the cytoplasm of THP-1 cells. By modelling the frequency dependence of the elastic modulus, the VIVA provides three metrics of cytoplasmic viscoelasticity: a low frequency modulus, a high frequency modulus and viscosity. The signature of cytotoxicity by rhodamine or silver exposure is a frequency independent twofold increase in the elastic modulus and cytoplasmic viscosity, while the cytoskeletal relaxation time remains unchanged. This is consistent with the known toxic mechanism of silver nanoparticles, where metabolic stress causes an increase in the rigidity of the cytoplasm. A variable indentation-rate viscoelastic analysis is presented as a straightforward method to promote the self-consistent comparison between cells. This is paramount to the development of early diagnosis and treatment of disease. PMID:26834855

  5. Particle number size distribution in the eastern Mediterranean: Formation and growth rates of ultrafine airborne atmospheric particles

    NASA Astrophysics Data System (ADS)

    Kopanakis, I.; Chatoutsidou, S. E.; Torseth, K.; Glytsos, T.; Lazaridis, M.

    2013-10-01

    Particle number concentration was measured between June 2009 and June 2010 at Akrotiri research station in a rural/suburban region of western Crete (Greece). Overall, the available data covered 157 days during the aforementioned period of measurements. The objectives were to study the number size distribution characteristics of ambient aerosols and furthermore to identify new particle formation events and to evaluate particle formation rates and growth rates of the newborn particles. Aerosol particles with mobility diameters between 10 and 1100 nm were measured using a Scanning Mobility Particle Sizer (SMPS) system. Measurements were performed at ambient relative humidities. The median total particle number concentration was 525 #/cm3 whereas the number concentration ranged between 130 #/cm3 and 9597 #/cm3. The average percentage of particles with diameters between 10 nm and 100 nm (N10-100) to total particles was 53% during summer and spring, but reached 80% during winter. Maximum average contribution of nano-particles (10 nm < Dp < 50 nm) to total particles was recorded also in winter and was attributed partly to the effect of local heating. Furthermore, back trajectories (HYSPLIT model) showed that different air mass origins are linked to different levels of particle number concentrations, with higher values associated with air masses passing from polluted areas before reaching the Akrotiri station. Modal analysis of the measured size distribution data revealed a strong nucleation mode during winter (15-25 nm), which can be correlated with emissions from local sources (domestic heating). The nucleation mode was observed also during the spring campaigns and was partly linked to new particle formation events. On the contrary, an accumulation mode (80-120 nm) prevailed in the measurements during summer campaigns, when the station area was influenced by polluted air masses arriving mainly from Eastern Europe. In total, 13 new particle formation events were recorded

  6. Local shear texture formation in adiabatic shear bands by high rate compression of high manganese TRIP steels

    NASA Astrophysics Data System (ADS)

    Li, J.; Yang, P.; Mao, W. M.; Cui, F. E.

    2015-04-01

    Local shear textures in ASBs of high manganese TRIP steels under high rate straining are determined and the influences of initial microstructure is analyzed using EBSD technique. It is seen that even at the presence of majority of two types of martensite before deformation, ASB is preferred to evolve in austenite, rather than in martenite, due to reverse transformation. Ultrafine grains of thress phases due to dynamic recrystallization are formed and all show shear textures. The less ε-martensite in ASB is distributed as islands and its preferred orientation can be found to originate from the variants in matrix. The grain orientation rotation around ASB in multi-phase alloy reveals significant influence of α'- martensite on texture in ASB. The mechanism of local texture formation in ASB of high manganese TRIP steel is proposed in terms of the interaction of early TRIP and later reverse transformation.

  7. Bacterial biofilm formation inhibitory activity revealed for plant derived natural compounds.

    PubMed

    Artini, M; Papa, R; Barbato, G; Scoarughi, G L; Cellini, A; Morazzoni, P; Bombardelli, E; Selan, L

    2012-01-15

    Use of herbal plant remedies to treat infectious diseases is a common practice in many countries in traditional and alternative medicine. However to date there are only few antimicrobial agents derived from botanics. Based on microbiological screening tests of crude plant extracts we identified four compounds derived from Krameria, Aesculus hippocastanum and Chelidonium majus that showed a potentially interesting antimicrobial activity. In this work we present an in depth characterization of the inhibition activity of these pure compounds on the formation of biofilm of Staphylococcus aureus as well as of Staphylococcus epidermidis strains. We show that two of these compounds possess interesting potential to become active principles of new drugs. PMID:22182580

  8. The accuracy of the UV continuum as an indicator of the star formation rate in galaxies

    NASA Astrophysics Data System (ADS)

    Wilkins, Stephen M.; Gonzalez-Perez, Violeta; Lacey, Cedric G.; Baugh, Carlton M.

    2012-12-01

    The rest-frame intrinsic UV luminosity is often used as an indicator of the instantaneous star formation rate (SFR) in a galaxy. While it is in general a robust indicator of the ongoing star formation activity, the precise value of the calibration relating the UV luminosity to the SFR (Bν) is sensitive to various physical properties, such as the recent star formation and metal enrichment histories, along with the choice of stellar initial mass function (IMF). The distribution of these properties for the star-forming galaxy population then suggests that the adoption of a single calibration is not appropriate unless properly qualified with the uncertainties on the calibration. We investigate, with the aid of the GALFORM semi-analytic model of galaxy formation, the distribution of UV-SFR calibrations obtained using realistic star formation and metal enrichment histories. At z = 0, we find that when the IMF is fixed (to the Kennicutt IMF), the median calibration is Bfuv = 0.9 where SFR/[M⊙ yr-1] = Bν × 10-28 × Lν/[erg s-1 Hz-1]. However, the width of the distribution Bfuv suggests that for a single object there is around a 20 per cent intrinsic uncertainty (at z = 0, rising to ≃30 per cent at z = 6) on the SFR inferred from the FUV luminosity without additional constraints on the star formation history or metallicity. We also find that the median value of the calibration Bfuv is correlated with the SFR and redshift (at z > 3) raising implications for the correct determination of the SFR from the UV.

  9. Proteome Analysis of Streptococcus thermophilus Grown in Milk Reveals Pyruvate Formate-Lyase as the Major Upregulated Protein

    PubMed Central

    Derzelle, Sylviane; Bolotin, Alexander; Mistou, Michel-Yves; Rul, Françoise

    2005-01-01

    We investigated the adaptation to milk of Streptococcus thermophilus LMG18311 using a proteomic approach. Two-dimensional electrophoresis of cytosolic proteins were performed after growth in M17 medium or in milk. A major modification of the proteome concerned proteins involved in the supply of amino acids, like the peptidase PepX, and several enzymes involved in amino acid biosynthesis. In parallel, we observed the upregulation of the synthesis of seven enzymes directly involved in the synthesis of purines, as well as formyl-tetrahydrofolate (THF) synthetase and serine hydroxy-methyl transferase, two enzymes responsible for the synthesis of compounds (THF and glycine, respectively) feeding the purine biosynthetic pathway. The analysis also revealed a massive increase in the synthesis of pyruvate formate-lyase (PFL), the enzyme which converts pyruvate into acetyl coenzyme A and formate. PFL has been essentially studied for its role in mixed-acid product formation in lactic acid bacteria during anaerobic fermentation. However, formate is an important methyl group donor for anabolic pathway through the formation of folate derivates. We hypothesized that PFL was involved in purine biosynthesis during growth in milk. We showed that PFL expression was regulated at the transcriptional level and that pfl transcription occurred during the exponential growth phase in milk. The complementation of milk with formate or purine bases was shown to reduce pfl expression, to suppress PFL synthesis, and to stimulate growth of S. thermophilus. These results show a novel regulatory mechanism controlling the synthesis of PFL and suggest an unrecognized physiological role for PFL as a formate supplier for anabolic purposes. PMID:16332852

  10. Covariance between Star Formation Rates and Dust Mass of KINGFISH Galaxies

    NASA Astrophysics Data System (ADS)

    Rojas Bolivar, Randall; Calzetti, Daniela; Dale, Daniel A.; Cook, David

    2016-01-01

    We present the initial results for a study of the potential covariance between galaxy physical parameters (e.g., the star formation rate and dust mass) derived from the infrared spectral energy distributions (SEDs) of galaxies. With the emergence of powerful facilities and instruments in the millimeter and sub-millimeter wavelengths, which complement data from infrared space telescopes like Herschel, scientists have been able to observe the infrared SEDs of faraway galaxies (with redshifts between 2 and 5). These SEDs are being used to derive both star formation rates (SFR) and dust masses, the latter related to gas masses. The relationship between SFRs and gas masses determine the fundamental scaling laws of star formation (the Schmidt Kennicutt Law). Thus, it is fundamental to ascertain whether derivation of these quantities from IR SEDs may be affected by covariance. We will use the Spitzer and Herschel data from the nearby survey: Key Insights on Nearby Galaxies: A Far-IR Survey with Herschel (KINGFISH), which includes 61 nearby galaxies observed between 3.6 and 500 micron.

  11. Mechanisms of endoderm formation in a cartilaginous fish reveal ancestral and homoplastic traits in jawed vertebrates

    PubMed Central

    Godard, Benoit G.; Coolen, Marion; Le Panse, Sophie; Gombault, Aurélie; Ferreiro-Galve, Susana; Laguerre, Laurent; Lagadec, Ronan; Wincker, Patrick; Poulain, Julie; Da Silva, Corinne; Kuraku, Shigehiro; Carre, Wilfrid; Boutet, Agnès; Mazan, Sylvie

    2014-01-01

    ABSTRACT In order to gain insight into the impact of yolk increase on endoderm development, we have analyzed the mechanisms of endoderm formation in the catshark S. canicula, a species exhibiting telolecithal eggs and a distinct yolk sac. We show that in this species, endoderm markers are expressed in two distinct tissues, the deep mesenchyme, a mesenchymal population of deep blastomeres lying beneath the epithelial-like superficial layer, already specified at early blastula stages, and the involuting mesendoderm layer, which appears at the blastoderm posterior margin at the onset of gastrulation. Formation of the deep mesenchyme involves cell internalizations from the superficial layer prior to gastrulation, by a movement suggestive of ingressions. These cell movements were observed not only at the posterior margin, where massive internalizations take place prior to the start of involution, but also in the center of the blastoderm, where internalizations of single cells prevail. Like the adjacent involuting mesendoderm, the posterior deep mesenchyme expresses anterior mesendoderm markers under the control of Nodal/activin signaling. Comparisons across vertebrates support the conclusion that endoderm is specified in two distinct temporal phases in the catshark as in all major osteichthyan lineages, in line with an ancient origin of a biphasic mode of endoderm specification in gnathostomes. They also highlight unexpected similarities with amniotes, such as the occurrence of cell ingressions from the superficial layer prior to gastrulation. These similarities may correspond to homoplastic traits fixed separately in amniotes and chondrichthyans and related to the increase in egg yolk mass. PMID:25361580

  12. Diversity in cell motility reveals the dynamic nature of the formation of zebrafish taste sensory organs.

    PubMed

    Soulika, Marina; Kaushik, Anna-Lila; Mathieu, Benjamin; Lourenço, Raquel; Komisarczuk, Anna Z; Romano, Sebastian Alejo; Jouary, Adrien; Lardennois, Alicia; Tissot, Nicolas; Okada, Shinji; Abe, Keiko; Becker, Thomas S; Kapsimali, Marika

    2016-06-01

    Taste buds are sensory organs in jawed vertebrates, composed of distinct cell types that detect and transduce specific taste qualities. Taste bud cells differentiate from oropharyngeal epithelial progenitors, which are localized mainly in proximity to the forming organs. Despite recent progress in elucidating the molecular interactions required for taste bud cell development and function, the cell behavior underlying the organ assembly is poorly defined. Here, we used time-lapse imaging to observe the formation of taste buds in live zebrafish larvae. We found that tg(fgf8a.dr17)-expressing cells form taste buds and get rearranged within the forming organs. In addition, differentiating cells move from the epithelium to the forming organs and can be displaced between developing organs. During organ formation, tg(fgf8a.dr17) and type II taste bud cells are displaced in random, directed or confined mode relative to the taste bud they join or by which they are maintained. Finally, ascl1a activity in the 5-HT/type III cell is required to direct and maintain tg(fgf8a.dr17)-expressing cells into the taste bud. We propose that diversity in displacement modes of differentiating cells acts as a key mechanism for the highly dynamic process of taste bud assembly. PMID:27122167

  13. Pattern Formation in the Arabidopsis Embryo Revealed by Position-Specific Lipid Transfer Protein Gene Expression.

    PubMed Central

    Vroemen, C. W.; Langeveld, S.; Mayer, U.; Ripper, G.; Jurgens, G.; Van Kammen, A.; De Vries, S. C.

    1996-01-01

    During Arabidopsis embryogenesis, the zygote divides asymmetrically in the future apical-basal axis; however, a radial axis is initiated only within the eight-celled embryo. Mutations in the GNOM, KNOLLE, and KEULE genes affect these processes: gnom zygotes tend to divide symmetrically; knolle embryos lack oriented cell divisions that initiate protoderm formation; and in keule embryos, an outer cell layer is present that consists of abnormally enlarged cells from early development. Pattern formation along the two axes is reflected by the position-specific expression of the Arabidopsis lipid transfer protein (AtLTP1) gene. In wild-type embryos, the AtLTP1 gene is expressed in the protoderm and initially in all protodermal cells; later, AtLTP1 expression is confined to the cotyledons and the upper end of the hypocotyl. Analysis of AtLTP1 expression in gnom, knolle, and keule embryos showed that gnom embryos also can have no or reversed apical-basal polarity, whereas radial polarity is unaffected. knolle embryos initially lack but eventually form a radial pattern, and keule embryos are affected in protoderm cell morphology rather than in the establishment of the radial pattern. PMID:12239400

  14. Metabolomics reveals the formation of aldehydes and iminium in gefitinib metabolism.

    PubMed

    Liu, Xing; Lu, Yuanfu; Guan, Xinfu; Dong, Bingning; Chavan, Hemantkumar; Wang, Jin; Zhang, Yiqing; Krishnamurthy, Partha; Li, Feng

    2015-09-01

    Gefitinib (GEF), an inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase, is widely used for the treatment of cancers, particularly non-small cell lung cancer. However, its clinical use is limited by multiple adverse effects associated with GEF, such as liver and lung injuries, severe nausea, and diarrhea. Although, the exact mechanism of GEF adverse effects are still unknown, xenobiotic-induced bioactivation is thought to play a significant role in GEF induced toxicity. Using a metabolomic approach, we investigated the metabolic pathways of GEF in human and mouse liver microsomes. Thirty four GEF metabolites and adducts were identified and half of them are novel. The potential reactive metabolites, two aldehydes and one iminium, were identified for the first time. The previously reported GSH adducts and primary amines were observed as well. The aldehyde and iminium pathways were further confirmed by using methoxylamine and potassium cyanide as trapping reagents. Using recombinant CYP450 isoforms, CYP3A4 inhibitor, and S9 from Cyp3a-null mice, we confirmed CYP3A is the major enzyme contributing to the formation of aldehydes, GSH adducts, and primary amines in liver. Multiple enzymes contribute to the formation of iminium. This study provided us more knowledge of GEF bioactivation and enzymes involved in metabolic pathways, which can be utilized for understanding the mechanism of adverse effects associated with GEF and predicting possible drug-drug interactions. Further studies are suggested to determine the roles of these bioactivation pathways in GEF toxicity. PMID:26212543

  15. Comparative analyses of evolutionary rates reveal different pathways to encephalization in bats, carnivorans, and primates

    PubMed Central

    Smaers, Jeroen B.; Dechmann, Dina K. N.; Goswami, Anjali; Soligo, Christophe; Safi, Kamran

    2012-01-01

    Variation in relative brain size is commonly interpreted as the result of selection on neuronal capacity. However, this approach ignores that relative brain size is also linked to another highly adaptive variable: body size. Considering that one-way tradeoff mechanisms are unlikely to provide satisfactory evolutionary explanations, we introduce an analytical framework that describes and quantifies all possible evolutionary scenarios between two traits. To investigate the effects of body mass changes on the interpretation of relative brain size evolution, we analyze three mammalian orders that are expected to be subject to different selective pressures on body size due to differences in locomotor adaptation: bats (powered flight), primates (primarily arboreal), and carnivorans (primarily terrestrial). We quantify rates of brain and body mass changes along individual branches of phylogenetic trees using an adaptive peak model of evolution. We find that the magnitude and variance of the level of integration of brain and body mass rates, and the subsequent relative influence of either brain or body size evolution on the brain–body relationship, differ significantly between orders and subgroups within orders. Importantly, we find that variation in brain–body relationships was driven primarily by variability in body mass. Our approach allows a more detailed interpretation of correlated trait evolution and variation in the underlying evolutionary pathways. Results demonstrate that a principal focus on interpreting relative brain size evolution as selection on neuronal capacity confounds the effects of body mass changes, thereby hiding important aspects that may contribute to explaining animal diversity. PMID:23071335

  16. Transcription rate and transcript length drive formation of chromosomal interaction domain boundaries.

    PubMed

    Le, Tung Bk; Laub, Michael T

    2016-07-15

    Chromosomes in all organisms are highly organized and divided into multiple chromosomal interaction domains, or topological domains. Regions of active, high transcription help establish and maintain domain boundaries, but precisely how this occurs remains unclear. Here, using fluorescence microscopy and chromosome conformation capture in conjunction with deep sequencing (Hi-C), we show that in Caulobacter crescentus, both transcription rate and transcript length, independent of concurrent translation, drive the formation of domain boundaries. We find that long, highly expressed genes do not form topological boundaries simply through the inhibition of supercoil diffusion. Instead, our results support a model in which long, active regions of transcription drive local decompaction of the chromosome, with these more open regions of the chromosome forming spatial gaps in vivo that diminish contacts between DNA in neighboring domains. These insights into the molecular forces responsible for domain formation in Caulobacter likely generalize to other bacteria and possibly eukaryotes. PMID:27288403

  17. Bifurcation and neck formation as a precursor to ductile fracture during high rate extension

    SciTech Connect

    Freund, L.B.; Soerensen, N.J.

    1997-12-31

    A block of ductile material, typically a segment of a plate or shell, being deformed homogeneously in simple plane strain extension commonly undergoes a bifurcation in deformation mode to nonuniform straining in the advanced stages of plastic flow. The focus here is on the influence of material inertia on the bifurcation process, particularly on the formation of diffuse necks as precursors to dynamic ductile fracture. The issue is considered from two points of view, first within the context of the theory of bifurcation of rate-independent, incrementally linear materials and then in terms of the complete numerical solution of a boundary value problem for an elastic-viscoplastic material. It is found that inertia favors the formation of relatively short wavelength necks as observed in shaped charge break-up and dynamic fragmentation.

  18. Analysis of carrier gas flow rate effect on hydroxyapatite particle formation in ultrasonic spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Widiyastuti, W.; Setiawan, Adhi; Nurtono, Tantular; Winardi, Sugeng

    2016-02-01

    Ultrasonic spray pyrolysis has been well-known process for producing fine particles from single and multicomponent materials. Here, the effect of carrier gas flow rate in ultrasonic spray pyrolysis process was studied in the particle formation of hydroxyapatite using solution precursor of Ca(CH3COO)2 and (NH4)2HPO4 with Ca/P ratio of 1.67. The experimental analysis was accompanied with computational fluid dynamics (CFD) simulation for comparison. In the simulation, the evaporation of the solvent in the droplets, a second evaporation due to crust formation, the decomposition reaction of the precursor involving the transfer of heat and mass transfer from droplet to surrounding were considered. By maintaining temperature at 900 °C, the residence time increased with decreasing the carrier gas flow rate led to the increasing the evaporation rate and the reacted fraction of the precursor. The predicted and experimental results of average particles size were agreed well with discrepancy 6.3%.

  19. Inverted micellar structures in bilayer membranes. Formation rates and half-lives.

    PubMed Central

    Siegel, D P

    1984-01-01

    Two sorts of inverted micellar structures have previously been proposed to explain morphological and 31P-NMR observations of bilayer systems. These structures only form in systems with components that can adopt the inverse hexagonal (HII) phase. LIP (lipidic particles) are intrabilayer structures, whereas IMI (inverted micellar intermediates) are structures that form between apposed bilayers. Here, we calculate the formation rates and half-lives of these structures to determine which (or if either) of these proposed structures is a likely explanation of the data. Calculations for the egg phosphatidylethanolamine and the Ca+-cardiolipin systems show that IMI form orders of magnitude faster than LIP, which should form slowly, if at all. This result is probably true in general, and indicates that "lipidic particle" electron micrograph images probably represent interbilayer structures, as some have previously proposed. It is shown here that IMI are likely intermediates in the lamellar----HII phase transitions and in the process of membrane fusion in some systems. The calculated formation rates, half-lives, and vesicle-vesicle fusion rates are in agreement with this observation. PMID:6365189

  20. The Spitzer c2d Legacy Results: Star-Formation Rates and Efficiencies; Evolution and Lifetimes

    NASA Astrophysics Data System (ADS)

    Evans, Neal J., II; Dunham, Michael M.; Jørgensen, Jes K.; Enoch, Melissa L.; Merín, Bruno; van Dishoeck, Ewine F.; Alcalá, Juan M.; Myers, Philip C.; Stapelfeldt, Karl R.; Huard, Tracy L.; Allen, Lori E.; Harvey, Paul M.; van Kempen, Tim; Blake, Geoffrey A.; Koerner, David W.; Mundy, Lee G.; Padgett, Deborah L.; Sargent, Anneila I.

    2009-04-01

    The c2d Spitzer Legacy project obtained images and photometry with both IRAC and MIPS instruments for five large, nearby molecular clouds. Three of the clouds were also mapped in dust continuum emission at 1.1 mm, and optical spectroscopy has been obtained for some clouds. This paper combines information drawn from studies of individual clouds into a combined and updated statistical analysis of star-formation rates and efficiencies, numbers and lifetimes for spectral energy distribution (SED) classes, and clustering properties. Current star-formation efficiencies range from 3% to 6%; if star formation continues at current rates for 10 Myr, efficiencies could reach 15-30%. Star-formation rates and rates per unit area vary from cloud to cloud; taken together, the five clouds are producing about 260 M sun of stars per Myr. The star-formation surface density is more than an order of magnitude larger than would be predicted from the Kennicutt relation used in extragalactic studies, reflecting the fact that those relations apply to larger scales, where more diffuse matter is included in the gas surface density. Measured against the dense gas probed by the maps of dust continuum emission, the efficiencies are much higher, with stellar masses similar to masses of dense gas, and the current stock of dense cores would be exhausted in 1.8 Myr on average. Nonetheless, star formation is still slow compared to that expected in a free-fall time, even in the dense cores. The derived lifetime for the Class I phase is 0.54 Myr, considerably longer than some estimates. Similarly, the lifetime for the Class 0 SED class, 0.16 Myr, with the notable exception of the Ophiuchus cloud, is longer than early estimates. If photometry is corrected for estimated extinction before calculating class indicators, the lifetimes drop to 0.44 Myr for Class I and to 0.10 for Class 0. These lifetimes assume a continuous flow through the Class II phase and should be considered median lifetimes or half

  1. NACA deficiency reveals the crucial role of somite-derived stromal cells in haematopoietic niche formation.

    PubMed

    Murayama, Emi; Sarris, Milka; Redd, Michael; Le Guyader, Dorothée; Vivier, Catherine; Horsley, Wyatt; Trede, Nikolaus; Herbomel, Philippe

    2015-01-01

    The ontogeny of haematopoietic niches in vertebrates is essentially unknown. Here we show that the stromal cells of the caudal haematopoietic tissue (CHT), the first niche where definitive haematopoietic stem/progenitor cells (HSPCs) home in zebrafish development, derive from the caudal somites through an epithelial-mesenchymal transition (EMT). The resulting stromal cell progenitors accompany the formation of the caudal vein sinusoids, the other main component of the CHT niche, and mature into reticular cells lining and interconnecting sinusoids. We characterize a zebrafish mutant defective in definitive haematopoiesis due to a deficiency in the nascent polypeptide-associated complex alpha subunit (NACA). We demonstrate that the defect resides not in HSPCs but in the CHT niche. NACA-deficient stromal cell progenitors initially develop normally together with the sinusoids, and HSPCs home to the resulting niche, but stromal cell maturation is compromised, leading to a niche that is unable to support HSPC maintenance, expansion and differentiation. PMID:26411530

  2. Transcriptional profiling reveals regulated genes in the hippocampus during memory formation

    NASA Technical Reports Server (NTRS)

    Donahue, Christine P.; Jensen, Roderick V.; Ochiishi, Tomoyo; Eisenstein, Ingrid; Zhao, Mingrui; Shors, Tracey; Kosik, Kenneth S.

    2002-01-01

    Transcriptional profiling (TP) offers a powerful approach to identify genes activated during memory formation and, by inference, the molecular pathways involved. Trace eyeblink conditioning is well suited for the study of regional gene expression because it requires the hippocampus, whereas the highly parallel task, delay conditioning, does not. First, we determined when gene expression was most regulated during trace conditioning. Rats were exposed to 200 trials per day of paired and unpaired stimuli each day for 4 days. Changes in gene expression were most apparent 24 h after exposure to 200 trials. Therefore, we profiled gene expression in the hippocampus 24 h after 200 trials of trace eyeblink conditioning, on multiple arrays using additional animals. Of 1,186 genes on the filter array, seven genes met the statistical criteria and were also validated by real-time polymerase chain reaction. These genes were growth hormone (GH), c-kit receptor tyrosine kinase (c-kit), glutamate receptor, metabotropic 5 (mGluR5), nerve growth factor-beta (NGF-beta), Jun oncogene (c-Jun), transmembrane receptor Unc5H1 (UNC5H1), and transmembrane receptor Unc5H2 (UNC5H2). All these genes, except for GH, were downregulated in response to trace conditioning. GH was upregulated; therefore, we also validated the downregulation of the GH inhibitor, somatostatin (SST), even though it just failed to meet criteria on the arrays. By during situ hybridization, GH was expressed throughout the cell layers of the hippocampus in response to trace conditioning. None of the genes regulated in trace eyeblink conditioning were similarly affected by delay conditioning, a task that does not require the hippocampus. These findings demonstrate that transcriptional profiling can exhibit a repertoire of genes sensitive to the formation of hippocampal-dependent associative memories.

  3. Localized Upper Tropospheric Warming During Tropical Depression and Storm Formation Revealed by the NOAA-15 AMSU

    NASA Technical Reports Server (NTRS)

    Spencer, Roy W.; Braswell, William D.

    1999-01-01

    The warm core of hurricanes as measured by microwave temperature sounders has been related to various azimuthally averaged measures of hurricane strength by several researchers Unfortunately, the use of these instruments (e.g. the Microwave Sounding Units, MSU) for the routine monitoring of tropical cyclone genesis and intensity has been hampered by poor resolution. The recent launch of the NOAA-15 AMSU represents a significant advance in our ability to monitor subtle atmospheric temperature variations (0.1-0.2 C) at relatively high spatial resolution (50 km) in the presence of clouds. Of particular interest is the possible capability of the AMSU to observe the slight warming associated with depression formation, and the relationship of the spatial characteristics of the warming to the surface pressure and wind field, without azimuthal averaging. In order to present the AMSU data as imagery, we have developed a method for precise limb-correction of all 15 AMSU channels. Through a linear combination of several neighboring channels, we can very closely match the nadir weighting functions of a given AMSU sounding channel with the non-nadir data. It is found that there is discernible, localized upper tropospheric warming associated with depression formation in the Atlantic basin during the 1998 hurricane season. Also, it is found that uncertainty in positioning of tropical cyclone circulation centers can be reduced, as in the example of Hurricane Georges as it approached Cuba. Finally, to explore the potential utility of a future high resolution microwave temperature sounder, we present an analysis of the relationship between the modeled surface wind field and simulated high -resolution AMSU-type measurements, based upon cloud resolving model simulations of hurricane Andrew in 1992.

  4. Transcriptional profiling reveals regulated genes in the hippocampus during memory formation.

    PubMed

    Donahue, Christine P; Jensen, Roderick V; Ochiishi, Tomoyo; Eisenstein, Ingrid; Zhao, Mingrui; Shors, Tracey; Kosik, Kenneth S

    2002-01-01

    Transcriptional profiling (TP) offers a powerful approach to identify genes activated during memory formation and, by inference, the molecular pathways involved. Trace eyeblink conditioning is well suited for the study of regional gene expression because it requires the hippocampus, whereas the highly parallel task, delay conditioning, does not. First, we determined when gene expression was most regulated during trace conditioning. Rats were exposed to 200 trials per day of paired and unpaired stimuli each day for 4 days. Changes in gene expression were most apparent 24 h after exposure to 200 trials. Therefore, we profiled gene expression in the hippocampus 24 h after 200 trials of trace eyeblink conditioning, on multiple arrays using additional animals. Of 1,186 genes on the filter array, seven genes met the statistical criteria and were also validated by real-time polymerase chain reaction. These genes were growth hormone (GH), c-kit receptor tyrosine kinase (c-kit), glutamate receptor, metabotropic 5 (mGluR5), nerve growth factor-beta (NGF-beta), Jun oncogene (c-Jun), transmembrane receptor Unc5H1 (UNC5H1), and transmembrane receptor Unc5H2 (UNC5H2). All these genes, except for GH, were downregulated in response to trace conditioning. GH was upregulated; therefore, we also validated the downregulation of the GH inhibitor, somatostatin (SST), even though it just failed to meet criteria on the arrays. By during situ hybridization, GH was expressed throughout the cell layers of the hippocampus in response to trace conditioning. None of the genes regulated in trace eyeblink conditioning were similarly affected by delay conditioning, a task that does not require the hippocampus. These findings demonstrate that transcriptional profiling can exhibit a repertoire of genes sensitive to the formation of hippocampal-dependent associative memories. PMID:12542233

  5. Changes in the halo formation rates due to features in the primordial spectrum

    SciTech Connect

    Hazra, Dhiraj Kumar

    2013-03-01

    Features in the primordial scalar power spectrum provide a possible roadway to describe the outliers at the low multipoles in the WMAP data. Apart from the CMB angular power spectrum, these features can also alter the matter power spectrum and, thereby, the formation of the large scale structure. Carrying out a complete numerical analysis, we investigate the effects of primordial features on the formation rates of the halos. We consider a few different inflationary models that lead to features in the scalar power spectrum and an improved fit to the CMB data, and analyze the corresponding imprints on the formation of halos. Performing a Markov Chain Monte Carlo analysis with the WMAP seven year data and the SDSS halo power spectrum from LRG DR7 for the models of our interest, we arrive at the parameter space of the models allowed by the data. We illustrate that, inflationary potentials, such as the quadratic potential with sinusoidal modulations and the axion monodromy model, which generate certain repeated, oscillatory features in the inflationary perturbation spectrum, do not induce a substantial difference in the number density of halos at their best fit values, when compared with, say, a nearly scale invariant spectrum as is generated by the standard quadratic potential. However, we find that the number density and the formation rates of halos change by about 13–22% for halo masses ranging over 10{sup 4}–10{sup 14} M{sub s}un, for potential parameters that lie within 2-σ around the best fit values arrived at from the aforesaid joint constraints. We briefly discuss the implications of our results.

  6. Metatranscriptomics reveals temperature-driven functional changes in microbiome impacting cheese maturation rate.

    PubMed

    De Filippis, Francesca; Genovese, Alessandro; Ferranti, Pasquale; Gilbert, Jack A; Ercolini, Danilo

    2016-01-01

    Traditional cheeses harbour complex microbial consortia that play an important role in shaping typical sensorial properties. However, the microbial metabolism is considered difficult to control. Microbial community succession and the related gene expression were analysed during ripening of a traditional Italian cheese, identifying parameters that could be modified to accelerate ripening. Afterwards, we modulated ripening conditions and observed consistent changes in microbial community structure and function. We provide concrete evidence of the essential contribution of non-starter lactic acid bacteria in ripening-related activities. An increase in the ripening temperature promoted the expression of genes related to proteolysis, lipolysis and amino acid/lipid catabolism and significantly increases the cheese maturation rate. Moreover, temperature-promoted microbial metabolisms were consistent with the metabolomic profiles of proteins and volatile organic compounds in the cheese. The results clearly indicate how processing-driven microbiome responses can be modulated in order to optimize production efficiency and product quality. PMID:26911915

  7. Metatranscriptomics reveals temperature-driven functional changes in microbiome impacting cheese maturation rate

    PubMed Central

    De Filippis, Francesca; Genovese, Alessandro; Ferranti, Pasquale; Gilbert, Jack A.; Ercolini, Danilo

    2016-01-01

    Traditional cheeses harbour complex microbial consortia that play an important role in shaping typical sensorial properties. However, the microbial metabolism is considered difficult to control. Microbial community succession and the related gene expression were analysed during ripening of a traditional Italian cheese, identifying parameters that could be modified to accelerate ripening. Afterwards, we modulated ripening conditions and observed consistent changes in microbial community structure and function. We provide concrete evidence of the essential contribution of non-starter lactic acid bacteria in ripening-related activities. An increase in the ripening temperature promoted the expression of genes related to proteolysis, lipolysis and amino acid/lipid catabolism and significantly increases the cheese maturation rate. Moreover, temperature-promoted microbial metabolisms were consistent with the metabolomic profiles of proteins and volatile organic compounds in the cheese. The results clearly indicate how processing-driven microbiome responses can be modulated in order to optimize production efficiency and product quality. PMID:26911915

  8. Stochastic modeling reveals an evolutionary mechanism underlying elevated rates of childhood leukemia.

    PubMed

    Rozhok, Andrii I; Salstrom, Jennifer L; DeGregori, James

    2016-01-26

    Young children have higher rates of leukemia than young adults. This fact represents a fundamental conundrum, because hematopoietic cells in young children should have fewer mutations (including oncogenic ones) than such cells in adults. Here, we present the results of stochastic modeling of hematopoietic stem cell (HSC) clonal dynamics, which demonstrated that early HSC pools were permissive to clonal evolution driven by drift. We show that drift-driven clonal expansions cooperate with faster HSC cycling in young children to produce conditions that are permissive for accumulation of multiple driver mutations in a single cell. Later in life, clonal evolution was suppressed by stabilizing selection in the larger young adult pools, and it was driven by positive selection at advanced ages in the presence of microenvironmental decline. Overall, our results indicate that leukemogenesis is driven by distinct evolutionary forces in children and adults. PMID:26755588

  9. Using Herschel Far-Infrared Photometry to Constrain Star Formation Rates in CLASH Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Larson, Rebecca L.; Postman, Marc; Fogarty, Kevin

    2016-01-01

    The Cluster Lensing And Supernova survey with Hubble (CLASH) program obtained broadband images of 25 massive galaxy clusters in 16 passbands from the UV to the near-IR. The data was taken with the Wide-field Camera 3 (WFC3), and the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). These 25 clusters have also been observed in the mid-IR by Spitzer IRAC, the far-IR by the Herschel Space Observatory PACS and SPIRE, and in the x-ray by the Chandra and XMM observatories. We focused on the two brightest cluster galaxies (BCGs) in the survey (MACS1931.8-2653 and RXJ1532.9+3021) that have reddening-corrected UV-derived star formation rates (SFRs) > 100 M⊙ yr-1 as measured by Fogarty et al (2015). The inclusion of Herschel data provides unique constraints on dust content and independent estimates of the star formation rates in these interesting galaxies. We performed photometry on the five Herschel bands (100-500μm), and removed any contamination from other cluster members. We fit a UV-FIR SED to each galaxy to measure the bolometric dust luminosity (Lbol), which we use to derive the FIR obscured SFR. We calculate the sum of the measured UV unobscured SFR from the HST photometry and the FIR obscured SFR from the Herschel photometry to get a total SFR for these two BCGs. We compared this to the reddening-corrected SFRs and found they were in agreement within error. This confirms that the Kennicutt and Calzetti methods for calculating star formation rates are both applicable for these highly star-forming massive cluster galaxies.

  10. Mercury's Hollows: Depths, Estimation of Formation Rates, and the Nature of the Bright Haloes

    NASA Astrophysics Data System (ADS)

    Blewett, D. T.; Stadermann, A. C.; Chabot, N. L.; Denevi, B. W.; Ernst, C. M.; Xiao, Z.; Solomon, S. C.

    2015-12-01

    Mercury's hollows are shallow depressions, often with high-reflectance interiors and haloes. The fresh appearance of hollows indicates that they are relatively young features. Their morphology is suggestive of formation via sublimation-like loss of a volatile-bearing phase through solar heating, destruction by UV photolysis, contact with molten rock, or bombardment by micrometeoroids and/or ions. Hollows are found within the low-reflectance material (LRM) color unit. Following an examination of all MESSENGER images with pixel sizes <20 m and incidence angles <85°, shadow-length measurements made on 905 images yielded the depths of 2608 hollows. The mean depth is 24 ± 16 m. The narrow range of depths, despite formation within LRM units that are of much greater and more variable thickness, could result from development of a protective lag as the volatile-bearing phase is lost. The rate at which hollows form may be estimated as follows. The size-frequency distribution of Mercury rayed craters >4 km in diameter gives absolute model ages of 110 to 689 Ma, depending on the crater production model. The 41-km-diameter rayed crater Balanchine has a density of superposed craters similar to the average for all rayed craters, so we take Balanchine's age to be the population average. Hollows on Balanchine's floor are ~300 m wide. The average rate of hollows formation by horizontal scarp retreat for a 110 Ma model age would be 1 cm per 3700 Earth years. If Balanchine formed 689 Ma ago, then the average growth rate would be 1 cm per 23,000 yr. We also consider the mechanisms by which hollows form bright haloes. Calculations show that comet-style lofting of dust by sublimating gas is not important given Mercury's high surface gravitational acceleration. Instead, the bright haloes may form by condensation of sublimated material or by physical modification or chemical alteration of the surface by re-deposited sublimation products.

  11. Resolved Gas Kinematics in a Sample of Low-Redshift High Star-Formation Rate Galaxies

    NASA Astrophysics Data System (ADS)

    Varidel, Mathew; Pracy, Michael; Croom, Scott; Owers, Matt S.; Sadler, Elaine

    2016-03-01

    We have used integral field spectroscopy of a sample of six nearby (z 0.01-0.04) high star-formation rate (SFR ˜ 10-40 M_⊙ yr^{-1}) galaxies to investigate the relationship between local velocity dispersion and star-formation rate on sub-galactic scales. The low-redshift mitigates, to some extent, the effect of beam smearing which artificially inflates the measured dispersion as it combines regions with different line-of-sight velocities into a single spatial pixel. We compare the parametric maps of the velocity dispersion with the Hα flux (a proxy for local star-formation rate), and the velocity gradient (a proxy for the local effect of beam smearing). We find, even for these very nearby galaxies, the Hα velocity dispersion correlates more strongly with velocity gradient than with Hα flux-implying that beam smearing is still having a significant effect on the velocity dispersion measurements. We obtain a first-order non parametric correction for the unweighted and flux weighted mean velocity dispersion by fitting a 2D linear regression model to the spaxel-by-spaxel data where the velocity gradient and the Hα flux are the independent variables and the velocity dispersion is the dependent variable; and then extrapolating to zero velocity gradient. The corrected velocity dispersions are a factor of 1.3-4.5 and 1.3-2.7 lower than the uncorrected flux-weighted and unweighted mean line-of-sight velocity dispersion values, respectively. These corrections are larger than has been previously cited using disc models of the velocity and velocity dispersion field to correct for beam smearing. The corrected flux-weighted velocity dispersion values are σ m 20-50 km s-1.

  12. An empirical model for the galaxy luminosity and star formation rate function at high redshift

    NASA Astrophysics Data System (ADS)

    Mashian, Natalie; Oesch, Pascal A.; Loeb, Abraham

    2016-01-01

    Using the most recent measurements of the ultraviolet (UV) luminosity functions (LFs) and dust estimates of early galaxies, we derive updated dust-corrected star formation rate functions (SFRFs) at z ˜ 4-8, which we model to predict the evolution to higher redshifts, z > 8. We employ abundance matching techniques to calibrate a relation between galaxy star formation rate (SFR) and host halo mass Mh by mapping the shape of the observed SFRFs at z ˜ 4-8 to that of the halo mass function. The resulting scaling law remains roughly constant over this redshift range. We apply the average SFR-Mh relation to reproduce the observed SFR functions at 4 ≲ z ≲ 8 and also derive the expected UV LFs at higher redshifts. At z ˜ 9 and z ˜ 10 these model LFs are in excellent agreement with current observed estimates. Our predicted number densities and UV LFs at z > 10 indicate that James Webb Space Telescope will be able to detect galaxies out to z ˜ 15 with an extensive treasury sized program. We also derive the redshift evolution of the star formation rate density (SFRD) and associated reionization history by galaxies. Models which integrate down to the current HUDF12/XDF detection limit (MUV ˜ -17.7 mag) result in a SFRD that declines as (1 + z)-10.4 ± 0.3 at high redshift and fail to reproduce the observed cosmic microwave background electron scattering optical depth, τ ≃ 0.066, to within 1σ. On the other hand, we find that the inclusion of galaxies with SFRs well below the current detection limit (MUV < -5.7 mag) leads to a fully reionized universe by z ˜ 6.5 and an optical depth of τ ≃ 0.054, consistent with the recently derived Planck value at the 1σ level.

  13. The metallographic revealing of twin formation in ZrNb industrial alloys

    NASA Astrophysics Data System (ADS)

    Chirkin, A. V.; Al-Nakow, Abubakir S.; Sherif, Salem M.

    1991-01-01

    The method of metallographic analysis in polarized light has been employed to reveal twins in Zr-Nb industrial alloys after plastic deformation. The twins appear during tensile testing of transverse sheet samples when σ y is exceeded. Most of the twins look like regular strips in the sheet plane, symmetric and stably oriented against the rolling and tensile directions. These twins are co-operative and cross grains with identical crystallographic orientation; the textured material behaves here as a pseudomonocrystal. The twin width is determined not only by the twin type, but also by the degree of deformation and increases with it. The twinning contribution in the practical deformation process is not important, if the general deformation degree is above 5-8%.

  14. Resequencing Reveals Different Domestication Rate for BADH1 and BADH2 in Rice (Oryza sativa)

    PubMed Central

    He, Qiang; Yu, Jie; Kim, Tae-Sung; Cho, Yoo-Hyun; Lee, Young-Sang; Park, Yong-Jin

    2015-01-01

    BADH1 and BADH2 are two homologous genes, encoding betaine aldehyde dehydrogenase in rice. In the present study, we scanned BADHs sequences of 295 rice cultivars, and 10 wild rice accessions to determine the polymorphisms, gene functions and domestication of these two genes. A total of 16 alleles for BADH1 and 10 alleles for BADH2 were detected in transcribed region of cultivars and wild species. Association study showed that BADH1 has significant correlation with salt tolerance in rice during germination stage, the SNP (T/A) in exon 4 is highly correlated with salt tolerance index (STI) (P<10−4). While, BADH2 was only responsible for rice fragrance, of which two BADH2 alleles (8 bp deletion in exon 7 and C/T SNP in exon 13) explain 97% of aroma variation in our germplasm. Theses indicate that there are no overlapping functions between the two homologous genes. In addition, a large LD block was detected in BADH2 region, however, there was no large LD blocks in a 4-Mb region of BADH1. We found that BADH2 region only showed significant bias in Tajima’s D value from the balance. Extended haplotype homozygosity study revealed fragrant accessions had a large LD block that extended around the mutation site (8 bp deletion in exon 7) of BADH2, while both of the BADH1 alleles (T/A in exon 4) did not show large extended LD block. All these results suggested that BADH2 was domesticated during rice evolution, while BADH1 was not selected by human beings. PMID:26258482

  15. Resequencing Reveals Different Domestication Rate for BADH1 and BADH2 in Rice (Oryza sativa).

    PubMed

    He, Qiang; Yu, Jie; Kim, Tae-Sung; Cho, Yoo-Hyun; Lee, Young-Sang; Park, Yong-Jin

    2015-01-01

    BADH1 and BADH2 are two homologous genes, encoding betaine aldehyde dehydrogenase in rice. In the present study, we scanned BADHs sequences of 295 rice cultivars, and 10 wild rice accessions to determine the polymorphisms, gene functions and domestication of these two genes. A total of 16 alleles for BADH1 and 10 alleles for BADH2 were detected in transcribed region of cultivars and wild species. Association study showed that BADH1 has significant correlation with salt tolerance in rice during germination stage, the SNP (T/A) in exon 4 is highly correlated with salt tolerance index (STI) (P<10(-4)). While, BADH2 was only responsible for rice fragrance, of which two BADH2 alleles (8 bp deletion in exon 7 and C/T SNP in exon 13) explain 97% of aroma variation in our germplasm. Theses indicate that there are no overlapping functions between the two homologous genes. In addition, a large LD block was detected in BADH2 region, however, there was no large LD blocks in a 4-Mb region of BADH1. We found that BADH2 region only showed significant bias in Tajima's D value from the balance. Extended haplotype homozygosity study revealed fragrant accessions had a large LD block that extended around the mutation site (8 bp deletion in exon 7) of BADH2, while both of the BADH1 alleles (T/A in exon 4) did not show large extended LD block. All these results suggested that BADH2 was domesticated during rice evolution, while BADH1 was not selected by human beings. PMID:26258482

  16. Vacuum ultraviolet photolysis of hydrogenated amorphous carbons . I. Interstellar H2 and CH4 formation rates

    NASA Astrophysics Data System (ADS)

    Alata, I.; Cruz-Diaz, G. A.; Muñoz Caro, G. M.; Dartois, E.

    2014-09-01

    Context. The interstellar hydrogenated amorphous carbons (HAC or a-C:H) observed in the diffuse medium are expected to disappear in a few million years, according to the destruction time scale from laboratory measurements. The existence of a-C:H results from the equilibrium between photodesorption, radiolysis, hydrogenation and resilience of the carbonaceous network. During this processing, many species are therefore injected into the gas phase, in particular H2, but also small organic molecules, radicals or fragments. Aims: We perform experiments on interstellar a-C:H analogs to quantify the release of these species in the interstellar medium. Methods: The vacuum ultraviolet (VUV) photolysis of interstellar hydrogenated amorphous carbon analogs was performed at low (10 K) to ambient temperature, coupled to mass-spectrometry detection and temperature-programed desorption. Using deuterium isotopic substitution, the species produced were unambiguously separated from background contributions. Results: The VUV photolysis of hydrogenated amorphous carbons leads to the efficient production of H2 molecules, but also to small hydrocarbons. Conclusions: These species are formed predominantly in the bulk of the a-C:H analog carbonaceous network, in addition to the surface formation. Compared with species made by the recombination of H atoms and physisorbed on surfaces, they diffuse out at higher temperatures. In addition to the efficient production rate, it provides a significant formation route in environments where the short residence time scale for H atoms inhibits H2 formation on the surface, such as PDRs. The photolytic bulk production of H2 with carbonaceous hydrogenated amorphous carbon dust grains can provide a very large portion of the contribution to the H2 molecule formation. These dust grains also release small hydrocarbons (such as CH4) into the diffuse interstellar medium, which contribute to the formation of small carbonaceous radicals after being dissociated

  17. Transcriptomic analysis reveals ethylene as stimulator and auxin as regulator of adventitious root formation in petunia cuttings

    PubMed Central

    Druege, Uwe; Franken, Philipp; Lischewski, Sandra; Ahkami, Amir H.; Zerche, Siegfried; Hause, Bettina; Hajirezaei, Mohammad R.

    2014-01-01

    Adventitious root (AR) formation in the stem base (SB) of cuttings is the basis for propagation of many plant species and petunia is used as model to study this developmental process. Following AR formation from 2 to 192 hours post-excision (hpe) of cuttings, transcriptome analysis by microarray revealed a change of the character of the rooting zone from SB to root identity. The greatest shift in the number of differentially expressed genes was observed between 24 and 72 hpe, when the categories storage, mineral nutrient acquisition, anti-oxidative and secondary metabolism, and biotic stimuli showed a notable high number of induced genes. Analyses of phytohormone-related genes disclosed multifaceted changes of the auxin transport system, auxin conjugation and the auxin signal perception machinery indicating a reduction in auxin sensitivity and phase-specific responses of particular auxin-regulated genes. Genes involved in ethylene biosynthesis and action showed a more uniform pattern as a high number of respective genes were generally induced during the whole process of AR formation. The important role of ethylene for stimulating AR formation was demonstrated by the application of inhibitors of ethylene biosynthesis and perception as well as of the precursor aminocyclopropane-1-carboxylic acid, all changing the number and length of AR. A model is proposed showing the putative role of polar auxin transport and resulting auxin accumulation in initiation of subsequent changes in auxin homeostasis and signal perception with a particular role of Aux/IAA expression. These changes might in turn guide the entrance into the different phases of AR formation. Ethylene biosynthesis, which is stimulated by wounding and does probably also respond to other stresses and auxin, acts as important stimulator of AR formation probably via the expression of ethylene responsive transcription factor genes, whereas the timing of different phases seems to be controlled by auxin. PMID

  18. REGULATION OF STAR FORMATION RATES IN MULTIPHASE GALACTIC DISKS: A THERMAL/DYNAMICAL EQUILIBRIUM MODEL

    SciTech Connect

    Ostriker, Eve C.; McKee, Christopher F.; Leroy, Adam K. E-mail: cmckee@astro.berkeley.ed

    2010-10-01

    We develop a model for the regulation of galactic star formation rates {Sigma}{sub SFR} in disk galaxies, in which interstellar medium (ISM) heating by stellar UV plays a key role. By requiring that thermal and (vertical) dynamical equilibrium are simultaneously satisfied within the diffuse gas, and that stars form at a rate proportional to the mass of the self-gravitating component, we obtain a prediction for {Sigma}{sub SFR} as a function of the total gaseous surface density {Sigma} and the midplane density of stars+dark matter {rho}{sub sd}. The physical basis of this relationship is that the thermal pressure in the diffuse ISM, which is proportional to the UV heating rate and therefore to {Sigma}{sub SFR}, must adjust until it matches the midplane pressure value set by the vertical gravitational field. Our model applies to regions where {Sigma} {approx}< 100 M{sub sun} pc{sup -2}. In low-{Sigma}{sub SFR} (outer-galaxy) regions where diffuse gas dominates, the theory predicts that {Sigma}{sub SFR{proportional_to}{Sigma}{radical}}({rho}{sub sd}). The decrease of thermal equilibrium pressure when {Sigma}{sub SFR} is low implies, consistent with observations, that star formation can extend (with declining efficiency) to large radii in galaxies, rather than having a sharp cutoff at a fixed value of {Sigma}. The main parameters entering our model are the ratio of thermal pressure to total pressure in the diffuse ISM, the fraction of diffuse gas that is in the warm phase, and the star formation timescale in self-gravitating clouds; all of these are (at least in principle) direct observables. At low surface density, our model depends on the ratio of the mean midplane FUV intensity (or thermal pressure in the diffuse gas) to the star formation rate, which we set based on solar-neighborhood values. We compare our results to recent observations, showing good agreement overall for azimuthally averaged data in a set of spiral galaxies. For the large flocculent spiral

  19. Changes in the spectrum and rates of extracellular enzyme activities in seawater following aggregate formation

    NASA Astrophysics Data System (ADS)

    Ziervogel, K.; Steen, A. D.; Arnosti, C.

    2010-03-01

    Marine snow aggregates are heavily colonized by heterotrophic microorganisms that express high levels of hydrolytic activities, making aggregates hotspots for carbon remineralization in the ocean. To assess how aggregate formation influences the ability of seawater microbial communities to access organic carbon, we compared hydrolysis rates of six polysaccharides in coastal seawater after aggregates had been formed (via incubation on a roller table) with hydrolysis rates in seawater from the same site that had not incubated on a roller table (referred to as whole seawater). Hydrolysis rates in the aggregates themselves were up to three orders of magnitude higher on a volume basis than in whole seawater. The enhancement of enzyme activity in aggregates relative to whole seawater differed by substrate, suggesting that the enhancement was under cellular control, rather than due to factors such as lysis or grazing. A comparison of hydrolysis rates in whole seawater with those in aggregate-free seawater, i.e. the fraction of water from the roller bottles that did not contain aggregates, demonstrated a nuanced microbial response to aggregate formation. Activities of laminarinase and xylanase enzymes in aggregate-free seawater were higher than in whole seawater, while activities of chondroitin, fucoidan, and arabinogalactan hydrolyzing enzymes were lower than in whole seawater. These data suggest that aggregate formation enhanced production of laminarinase and xylanase enzymes, and the enhancement also affected the surrounding seawater. Decreased activities of chondroitin, fucoidan, and arabinoglactan-hydrolyzing enzymes in aggregate-free seawaters relative to whole seawater are likely due to shifts in enzyme production by the aggregate-associated community, coupled with the effects of enzyme degradation. Enhanced activities of laminarin- and xylan-hydrolyzing enzymes in aggregate-free seawater were due at least in part to cell-free enzymes. Measurements of enzyme

  20. Changes in the spectrum and rates of extracellular enzyme activities in seawater following aggregate formation

    NASA Astrophysics Data System (ADS)

    Ziervogel, K.; Steen, A. D.; Arnosti, C.

    2009-12-01

    Marine snow aggregates are heavily colonized by heterotrophic microorganisms that express high levels of hydrolytic activities, making aggregates hotspots for carbon remineralization in the ocean. To assess how aggregate formation influences the ability of seawater microbial communities to access organic carbon, we compared hydrolysis rates of six polysaccharides in coastal seawater after aggregates had been formed (via incubation on a roller table) with hydrolysis rates in seawater from the same site that had not incubated on a roller table (referred to as whole seawater). Hydrolysis rates in the aggregates themselves were up to three orders of magnitude higher on a volume basis than in whole seawater. The enhancement of enzyme activity in aggregates relative to whole seawater differed by substrate, suggesting that the enhancement was under cellular control, rather than due to factors such as lysis or grazing. A comparison of hydrolysis rates in whole seawater with those in aggregate-free seawater, i.e. the fraction of water from the roller bottles that did not contain aggregates, demonstrated a nuanced microbial response to aggregate formation. Activities of laminarinase and xylanase enzymes in aggregate-free seawater were higher than in whole seawater, while activities of chondroitin, fucoidan, and arabinogalactan hydrolyzing enzymes were lower than in whole seawater. These data suggest that aggregate formation enhanced production of laminarinase and xylanase enzymes, and the enhancement also affected the surrounding seawater. Decreased activities of chondroitin, fucoidan, and arabinoglactan-hydrolyzing enzymes in aggregate-free seawater relative to whole seawater are likely due to shifts in enzyme production by the aggregate-associated community, coupled with the effects of enzyme degradation. Enhanced activities of laminarin- and xylan-hydrolyzing enzymes in aggregate-free seawater were due at least in part to cell-free enzymes. Measurements of enzyme lifetime

  1. Reaction Rates for the Formation of Deuterium Tritide from Deuterium and Tritium

    SciTech Connect

    McConville, G. T.; Menke, D. A.; Ellefson, R. E.

    1985-04-01

    The rates of formation of DT in a mixture of D2 and T2 have been measured as a function of initial T2 concentration, pressure, temperature,and methane concentration in a stainless steel reaction container which had been treated to inhibit protium ingrowth. An attempt has been made to explain the experimental resuts on the basis of ion-molecule chain reactions. Some of the observations are consistent with a gas-phase ion, ground-state molecule reaction, but some of the more interesting observations require more complicated models. The addition of excited state molecules or heterogeneous catalytic effects are possibilities that will need further experiments for confirmation.

  2. Rate of Temperature Decay in Human Muscle Following 3 MHz Ultrasound: The Stretching Window Revealed

    PubMed Central

    Draper, David O.; Ricard, Mark D.

    1995-01-01

    Researchers have determined that when therapeutic ultrasound vigorously heats connective tissue, it can be effective in increasing extensibility of collagen affected by scar tissue. These findings give credence to the use of continuous thermal ultrasound to heat tissue before stretching, exercise, or friction massage in an effort to decrease joint contractures and increase range of motion. Before our investigation, it was not known how long following an ultrasound treatment the tissue will remain at a vigorous heating level (>3°C). We conducted this study to determine the rate of temperature decay following 3 MHz ultrasound, in order to determine the time period of optimal stretching. Twenty subjects had a 23-gauge hypodermic needle microprobe inserted 1.2 cm deep into the medial aspect of their anesthetized triceps surae muscle. Subjects then received a 3 MHz ultrasound treatment at 1.5 W/cm2 until the tissue temperature was increased at least 5°C. The mean baseline temperature before each treatment was 33.8 ± 1.3°C, and it peaked at 39.1 ± 1.2°C from the ultrasound. Immediately following the treatment, we recorded the rate at which the temperature dropped at 30-second intervals. We ran a stepwise nonlinear regression analysis to predict temperature decay as a function of time following ultrasound treatment. We found a significant nonlinear relationship between time and temperature decay. The average time it took for the temperature to drop each degree as expressed in minutes and seconds was: 1°C = 1:20; 2°C = 3:22; 3°C = 5:50; 4°C = 9:13; 5°C = 14:55; 5.3°C = 18:00 (baseline). We conclude that under similar circumstances where the tissue temperature is raised 5°C, stretching will be effective, on average, for 3.3 minutes following an ultrasound treatment. To increase this stretching window, we suggest that stretching be applied during and immediately after ultrasound application. ImagesFig 1.Fig 2. PMID:16558352

  3. Mutation biases and mutation rate variation around very short human microsatellites revealed by human-chimpanzee-orangutan genomic sequence alignments.

    PubMed

    Amos, William

    2010-09-01

    I have studied mutation patterns around very short microsatellites, focusing mainly on sequences carrying only two repeat units. By using human-chimpanzee-orangutan alignments, inferences can be made about both the relative rates of mutations and which bases have mutated. I find remarkable non-randomness, with mutation rate depending on a base's position relative to the microsatellite, the identity of the base itself and the motif in the microsatellite. Comparing the patterns around AC2 with those around other four-base combinations reveals that AC2 does not stand out as being special in the sense that non-repetitive tetramers also generate strong mutation biases. However, comparing AC2 and AC3 with AC4 reveals a step change in both the rate and nature of mutations occurring, suggesting a transition state, AC4 exhibiting an alternating high-low mutation rate pattern consistent with the sequence patterning seen around longer microsatellites. Surprisingly, most changes in repeat number occur through base substitutions rather than slippage, and the relative probability of gaining versus losing a repeat in this way varies greatly with repeat number. Slippage mutations reveal rather similar patterns of mutability compared with point mutations, being rare at two repeats where most cause the loss of a repeat, with both mutation rate and the proportion of expansion mutations increasing up to 6-8 repeats. Inferences about longer repeat tracts are hampered by uncertainties about the proportion of multi-species alignments that fail due to multi-repeat mutations and other rearrangements. PMID:20700734

  4. Metatranscriptomics reveals temperature-driven functional changes in microbiome impacting cheese maturation rate

    DOE PAGESBeta

    De Filippis, Francesca; Genovese, Alessandro; Ferranti, Pasquale; Gilbert, Jack A.; Ercolini, Danilo

    2016-02-25

    Traditional cheeses harbour complex microbial consortia that play an important role in shaping typical sensorial properties. However, the microbial metabolism is considered difficult to control. Microbial community succession and the related gene expression were analysed during ripening of a traditional Italian cheese, identifying parameters that could be modified to accelerate ripening. Afterwards, we modulated ripening conditions and observed consistent changes in microbial community structure and function. We provide concrete evidence of the essential contribution of non-starter lactic acid bacteria in ripening-related activities. An increase in the ripening temperature promoted the expression of genes related to proteolysis, lipolysis and amino acid/lipidmore » catabolism and significantly increases the cheese maturation rate. Moreover, temperature-promoted microbial metabolisms were consistent with the metabolomic profiles of proteins and volatile organic compounds in the cheese. Finally, the results clearly indicate how processing-driven microbiome responses can be modulated in order to optimize production efficiency and product quality.« less

  5. Structural Changes Associated with Transthyretin Misfolding and Amyloid Formation Revealed by Solution and Solid-State NMR.

    PubMed

    Lim, Kwang Hun; Dasari, Anvesh K R; Hung, Ivan; Gan, Zhehong; Kelly, Jeffery W; Wemmer, David E

    2016-04-01

    Elucidation of structural changes involved in protein misfolding and amyloid formation is crucial for unraveling the molecular basis of amyloid formation. Here we report structural analyses of the amyloidogenic intermediate and amyloid aggregates of transthyretin using solution and solid-state nuclear magnetic resonance (NMR) spectroscopy. Our solution NMR results show that one of the two main β-sheet structures (CBEF β-sheet) is maintained in the aggregation-competent intermediate, while the other DAGH β-sheet is more flexible on millisecond time scales. Magic-angle-spinning solid-state NMR revealed that AB loop regions interacting with strand A in the DAGH β-sheet undergo conformational changes, leading to the destabilized DAGH β-sheet. PMID:26998642

  6. Cryo-EM structure of aerolysin variants reveals a novel protein fold and the pore-formation process.

    PubMed

    Iacovache, Ioan; De Carlo, Sacha; Cirauqui, Nuria; Dal Peraro, Matteo; van der Goot, F Gisou; Zuber, Benoît

    2016-01-01

    Owing to their pathogenical role and unique ability to exist both as soluble proteins and transmembrane complexes, pore-forming toxins (PFTs) have been a focus of microbiologists and structural biologists for decades. PFTs are generally secreted as water-soluble monomers and subsequently bind the membrane of target cells. Then, they assemble into circular oligomers, which undergo conformational changes that allow membrane insertion leading to pore formation and potentially cell death. Aerolysin, produced by the human pathogen Aeromonas hydrophila, is the founding member of a major PFT family found throughout all kingdoms of life. We report cryo-electron microscopy structures of three conformational intermediates and of the final aerolysin pore, jointly providing insight into the conformational changes that allow pore formation. Moreover, the structures reveal a protein fold consisting of two concentric β-barrels, tightly kept together by hydrophobic interactions. This fold suggests a basis for the prion-like ultrastability of aerolysin pore and its stoichiometry. PMID:27405240

  7. Cryo-EM structure of aerolysin variants reveals a novel protein fold and the pore-formation process

    PubMed Central

    Iacovache, Ioan; De Carlo, Sacha; Cirauqui, Nuria; Dal Peraro, Matteo; van der Goot, F. Gisou; Zuber, Benoît

    2016-01-01

    Owing to their pathogenical role and unique ability to exist both as soluble proteins and transmembrane complexes, pore-forming toxins (PFTs) have been a focus of microbiologists and structural biologists for decades. PFTs are generally secreted as water-soluble monomers and subsequently bind the membrane of target cells. Then, they assemble into circular oligomers, which undergo conformational changes that allow membrane insertion leading to pore formation and potentially cell death. Aerolysin, produced by the human pathogen Aeromonas hydrophila, is the founding member of a major PFT family found throughout all kingdoms of life. We report cryo-electron microscopy structures of three conformational intermediates and of the final aerolysin pore, jointly providing insight into the conformational changes that allow pore formation. Moreover, the structures reveal a protein fold consisting of two concentric β-barrels, tightly kept together by hydrophobic interactions. This fold suggests a basis for the prion-like ultrastability of aerolysin pore and its stoichiometry. PMID:27405240

  8. Cryo-EM structure of aerolysin variants reveals a novel protein fold and the pore-formation process

    NASA Astrophysics Data System (ADS)

    Iacovache, Ioan; de Carlo, Sacha; Cirauqui, Nuria; Dal Peraro, Matteo; van der Goot, F. Gisou; Zuber, Benoît

    2016-07-01

    Owing to their pathogenical role and unique ability to exist both as soluble proteins and transmembrane complexes, pore-forming toxins (PFTs) have been a focus of microbiologists and structural biologists for decades. PFTs are generally secreted as water-soluble monomers and subsequently bind the membrane of target cells. Then, they assemble into circular oligomers, which undergo conformational changes that allow membrane insertion leading to pore formation and potentially cell death. Aerolysin, produced by the human pathogen Aeromonas hydrophila, is the founding member of a major PFT family found throughout all kingdoms of life. We report cryo-electron microscopy structures of three conformational intermediates and of the final aerolysin pore, jointly providing insight into the conformational changes that allow pore formation. Moreover, the structures reveal a protein fold consisting of two concentric β-barrels, tightly kept together by hydrophobic interactions. This fold suggests a basis for the prion-like ultrastability of aerolysin pore and its stoichiometry.

  9. Conditional Deletion of Prolyl Hydroxylase Domain-Containing Protein 2 (Phd2) Gene Reveals Its Essential Role in Chondrocyte Function and Endochondral Bone Formation.

    PubMed

    Cheng, Shaohong; Xing, Weirong; Pourteymoor, Sheila; Schulte, Jan; Mohan, Subburaman

    2016-01-01

    The hypoxic growth plate cartilage requires hypoxia-inducible factor (HIF)-mediated pathways to maintain chondrocyte survival and differentiation. HIF proteins are tightly regulated by prolyl hydroxylase domain-containing protein 2 (Phd2)-mediated proteosomal degradation. We conditionally disrupted the Phd2 gene in chondrocytes by crossing Phd2 floxed mice with type 2 collagen-α1-Cre transgenic mice and found massive increases (>50%) in the trabecular bone mass of long bones and lumbar vertebra of the Phd2 conditional knockout (cKO) mice caused by significant increases in trabecular number and thickness and reductions in trabecular separation. Cortical thickness and tissue mineral density at the femoral middiaphysis of the cKO mice were also significantly increased. Dynamic histomorphometric analyses revealed increased longitudinal length and osteoid surface per bone surface in the primary spongiosa of the cKO mice, suggesting elevated conversion rate from hypertrophic chondrocytes to mineralized bone matrix as well as increased bone formation in the primary spongiosa. In the secondary spongiosa, bone formation measured by mineralizing surface per bone surface and mineral apposition rate were not changed, but resorption was slightly reduced. Increases in the mRNA levels of SRY (sex determining region Y)-box 9, osterix (Osx), type 2 collagen, aggrecan, alkaline phosphatase, bone sialoprotein, vascular endothelial growth factor, erythropoietin, and glycolytic enzymes in the growth plate of cKO mice were detected by quantitative RT-PCR. Immunohistochemistry revealed an increased HIF-1α protein level in the hypertrophic chondrocytes of cKO mice. Infection of chondrocytes isolated from Phd2 floxed mice with adenoviral Cre resulted in similar gene expression patterns as observed in the cKO growth plate chondrocytes. Our findings indicate that Phd2 suppresses endochondral bone formation, in part, via HIF-dependent mechanisms in mice. PMID:26562260

  10. Transcriptome analysis reveals physiological characteristics required for magnetosome formation in Magnetospirillum gryphiswaldense MSR-1.

    PubMed

    Wang, Xu; Wang, Qing; Zhang, Yang; Wang, Yinjia; Zhou, Yuan; Zhang, Weijia; Wen, Tong; Li, Li; Zuo, Meiqing; Zhang, Ziding; Tian, Jiesheng; Jiang, Wei; Li, Ying; Wang, Lei; Li, Jilun

    2016-06-01

    Magnetosome synthesis ability of Magnetospirillum gryphiswaldense MSR-1 in an autofermentor can be precisely controlled through strict control of dissolved oxygen concentration. In this study, using transcriptome data we discovered gene transcriptional differences and compared physiological characteristics of MSR-1 cells cultured under aerobic (high-oxygen) and micro-aerobic (low-oxygen) conditions. The results showed that 77 genes were up-regulated and 95 genes were down-regulated significantly under micro-aerobic situation. These genes were involved primarily in the categories of cell metabolism, transport, regulation and unknown-function proteins. The nutrient transport and physiological metabolism were slowed down under micro-aerobic condition, whereas dissimilatory denitrification pathways were activated and it may supplemental energy was made available for magnetosome synthesis. The result suggested that the genes of magnetosome membrane proteins (Mam and Mms) are not directly regulated by oxygen level, or are constitutively expressed. A proposed regulatory network of differentially expressed genes reflects the complexity of physiological metabolism in MSR-1, and suggests that some yet-unknown functional proteins play important roles such as ferric iron uptake and transport during magnetosome synthesis. The transcriptome data provides a holistic view of the responses of MSR-1 cells to differing oxygen levels. This approach will give new insights into general principles of magnetosome formation. PMID:27043321

  11. A New DTA Method for Measuring Critical Cooling Rate for Glass Formation

    NASA Technical Reports Server (NTRS)

    Ray, Chandra S.; Reis, Signo T.; Brow, Richard K.; Holand, Wolfram; Rheinberger, Volker

    2004-01-01

    A new differential thermal analysis (DTA) experimental method has been developed to determine the critical cooling rate for glass formation, R(sub c). The method, which is found especially suitable for melts that, upon cooling, have a small heat of crystallization or a very slow crystallization rate, has been verified using a 38Na2O-62SiO2 (mol%) melt with a known R(sub c) (-approx. 19 C/min), then used to determine R(sub c) for two complex lithium silicate glass forming melts. The new method is rapid, easy to conduct and yields values for R(sub c) that are in excellent agreement with the R(sub c)-values measured by standard DTA techniques.

  12. Gas-Phase Formation Rates of Nitric Acid and Its Isomers Under Urban Conditions

    NASA Technical Reports Server (NTRS)

    Okumura, M.; Mollner, A. K.; Fry, J. L.; Feng, L.

    2005-01-01

    Ozone formation in urban smog is controlled by a complex set of reactions which includes radical production from photochemical processes, catalytic cycles which convert NO to NO2, and termination steps that tie up reactive intermediates in long-lived reservoirs. The reaction OH + NO2 + M -4 HONO2 + M (la) is a key termination step because it transforms two short-lived reactive intermediates, OH and NO2, into relatively long-lived nitric acid. Under certain conditions (low VOC/NOx), ozone production in polluted urban airsheds can be highly sensitive to this reaction, but the rate parameters are not well constrained. This report summarizes the results of new laboratory studies of the OH + NO2 + M reaction including direct determination of the overall rate constant and branching ratio for the two reaction channels under atmospherically relevant conditions.

  13. Linear free energy relationship rate constants and basicities of N-substituted phenyl glycines in positronium-glycine complex formation

    NASA Astrophysics Data System (ADS)

    Chen, Rongti; Liang, Jiachang; Du, Youming; Cao, Chun; Yin, Dinzhen; Wang, Shuying; Zhang, Tianbao

    1987-06-01

    Complex formation between positronium and glycine derivatives in solution is discussed and the complex reaction rate constants obtained by means of a positron annihilation lifetime spectrometer with BaF 2 detectors. Rate constants mainly depend on the conjugation effect at the benzene ring and the induction effect of the substituents at the phenyl. There is a linear free energy relationship between rate constants and basicities of N-substituted phenyl glycines in orthopositronium-glycine complex formation.

  14. Influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel films

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Anderoglu, O.; Misra, A.; Wang, H.

    2007-04-01

    The authors have studied the influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel thin films. Transmission electron microscopy shows that the volume fraction of twinned grains increases with increasing deposition rate, whereas the average columnar grain size and twin spacing stay approximately unchanged. These experimental results agree qualitatively with their analytical model that predicts deposition rate dependent formation of growth twins. The film hardness increases monotonically with increasing volume fraction of twinned grains.

  15. Influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel films

    SciTech Connect

    Zhang, X.; Anderoglu, O.; Misra, A.; Wang, H.

    2007-04-09

    The authors have studied the influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel thin films. Transmission electron microscopy shows that the volume fraction of twinned grains increases with increasing deposition rate, whereas the average columnar grain size and twin spacing stay approximately unchanged. These experimental results agree qualitatively with their analytical model that predicts deposition rate dependent formation of growth twins. The film hardness increases monotonically with increasing volume fraction of twinned grains.

  16. Controlling the relative rates of adlayer formation and removal during etching in inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Fuller, Nicholas Colvin Masi

    Laser desorption (LD) of the adlayer coupled with laser induced fluorescence (LIF) and plasma induced emission (PIE) of desorbed adsorbates is used to investigate the relative rates of chlorination and sputtering during the etching of Si in inductively coupled Cl2-Ar plasmas. Such an analysis is a two-fold process: surface analysis and plasma characterization. Surface analysis of Si etching using LD-LIF and LD-PIE techniques combined with etch rate measurements have revealed that the coverage of SiCl2 and etch rate increases and coverage of Si decreases abruptly for a chlorine fraction of 75% and ion energy of 80 eV. The precise Cl2 fraction for which these abrupt changes occur increases with an increase in ion energy. These changes may be caused by local chemisorption-induced reconstruction of Si <100>. Furthermore, the chlorination and sputtering rates are increased by ˜ an order of magnitude as the plasma is changed from Ar-dominant to Cl-dominant. Characterization of the plasma included determination of the dominant ion in Cl2 plasmas using LIF and a Langmuir probe and measurement of the absolute densities of Cl2, Cl, Cl+, and At + in Cl2-Ar discharges using optical emission actinometry. These studies reveal that Cl+ is the dominant positive ion in the H-mode and the dissociation of Cl2 to Cl increases with an increase in Ar fraction due to an increase in electron temperature. Furthermore, for powers exceeding 600 W, the neutral to ion flux ratio is strongly dependent on Cl2 fraction and is attributed mostly to the decrease in Cl density. Such dependence of the flux ratio on Cl2 fraction is significant in controlling chlorination and sputtering rates not only for Si etching, but for etching other key technological materials. ICP O2 discharges were also studied for low-kappa polymeric etch applications. These studies reveal that the electron temperature is weakly dependent on rf power and O2 dissociation is low (˜2%) at the maximum rf power density of 5.7 Wcm

  17. Ultrahigh-resolution imaging reveals formation of neuronal SNARE/Munc18 complexes in situ

    PubMed Central

    Pertsinidis, Alexandros; Mukherjee, Konark; Sharma, Manu; Pang, Zhiping P.; Park, Sang Ryul; Zhang, Yunxiang; Brunger, Axel T.; Südhof, Thomas C.; Chu, Steven

    2013-01-01

    Membrane fusion is mediated by complexes formed by SNAP-receptor (SNARE) and Secretory 1 (Sec1)/mammalian uncoordinated-18 (Munc18)-like (SM) proteins, but it is unclear when and how these complexes assemble. Here we describe an improved two-color fluorescence nanoscopy technique that can achieve effective resolutions of up to 7.5-nm full width at half maximum (3.2-nm localization precision), limited only by stochastic photon emission from single molecules. We use this technique to dissect the spatial relationships between the neuronal SM protein Munc18-1 and SNARE proteins syntaxin-1 and SNAP-25 (25 kDa synaptosome-associated protein). Strikingly, we observed nanoscale clusters consisting of syntaxin-1 and SNAP-25 that contained associated Munc18-1. Rescue experiments with syntaxin-1 mutants revealed that Munc18-1 recruitment to the plasma membrane depends on the Munc18-1 binding to the N-terminal peptide of syntaxin-1. Our results suggest that in a primary neuron, SNARE/SM protein complexes containing syntaxin-1, SNAP-25, and Munc18-1 are preassembled in microdomains on the presynaptic plasma membrane. Our superresolution imaging method provides a framework for investigating interactions between the synaptic vesicle fusion machinery and other subcellular systems in situ. PMID:23821748

  18. Contrasting behavior of oxygen and iron isotopes in banded iron formation revealed by in situ analysis

    NASA Astrophysics Data System (ADS)

    Beard, B.; Li, W.; Kita, N.; Valley, J. W.; Johnson, C.

    2012-12-01

    Banded iron formations (BIFs) record a period of dramatic secular change in Earth's geologic history, when abundant aqueous Fe(II) was removed from Archean and Proterozoic oceans by oxidation. BIFs are characterized by co-existing of quartz and iron minerals, including oxides and carbonates, and alternating iron-rich and iron-poor layers range from m to Formation, Hamersley Group, Western Australia. Oxygen isotope ratios were measured by Secondary Ion Mass Spectrometry (SIMS), and Fe isotope ratios were measured by femtosecond Laser ablation Multi-Collector ICP-MS (fs-LA-MC-ICP-MS), with spatial resolutions of 15 mm (O) and 30-50 mm (Fe), and external precisions (2s) of +0.7 ‰ for δ18O and +0.2 ‰ for δ56Fe, respectively. Analysis of δ18O in iron oxides by SIMS employed special tuning with a 3kV primary beam to minimize orientation effects (Huberty et al. 2010 ). For hematite, δ18O values range from -7.1 ‰ to -0.6 ‰, with the majority of data clustering around -4.5 ‰, and δ56Fe values range from -0.50 ‰ to +1.53‰. Magnetite has a δ18O range of -5.6 ‰ to +5.6 ‰ and a δ56Fe range of -0.76 ‰ to +1.33 ‰. Notably, magnetite shows significant O isotope heterogeneity at a mineral grain scale, and the highest δ18O values were commonly measured from Si-rich (1-3 wt% SiO2) magnetite overgrowths or magnetite grains that have a recrystallization texture. In contrast, lowest δ18O values were measured from magnetite that contains less than 1 wt% SiO2. Individual magnetite grains can have up to 6 ‰ variation in δ18O values between low-Si core and Si-rich overgrowth. Iron

  19. Expression and activity analysis reveal that heme oxygenase (decycling) 1 is associated with blue egg formation.

    PubMed

    Wang, Z P; Liu, R F; Wang, A R; Li, J Y; Deng, X M

    2011-04-01

    Biliverdin is responsible for the coloration of blue eggs and is secreted onto the eggshell by the shell gland. Previous studies confirmed that a significant difference exists in biliverdin content between blue eggs and brown eggs, although the reasons are still unknown. Because the pigment is derived from oxidative degradation of heme catalyzed by heme oxygenase (HO), this study compared heme oxygenase (decycling) 1 (HMOX1), the gene encoding HO expression and HO activity, in the shell glands of the Dongxiang blue-shelled chicken (n = 12) and the Dongxiang brown-shelled chicken (n = 12). Results showed that HMOX1 was highly expressed at the mRNA (1.58-fold; P < 0.05) and protein levels in blue-shelled chickens compared with brown-shelled chickens. At the functional level, blue-shelled chickens also showed 1.40-fold (P < 0.05) higher HO activity than brown-shelled chickens. To explore the reasons for the differential expression of HMOX1, an association study of 6 SNP capturing the majority of HMOX1 variants with the blue egg coloration was performed. Results showed no significant association between SNP and the blue egg coloration in HMOX1 (P > 0.05). Taken together, these results show that blue egg formation is associated with high expression of HMOX1 in the shell gland of Dongxiang blue-shelled chickens, and suggest that differential expression of HMOX1 in the 2 groups of chickens is most likely to arise from an alteration in the trans-acting factor. PMID:21406370

  20. Come to China! Calibration of Star Formation Rates Across the Electromagnetic Spectrum

    NASA Astrophysics Data System (ADS)

    Hornschemeier, Ann E.; Zezas, A.; Calzetti, D.

    2011-09-01

    Measuring and mapping star-forming activity in galaxies is a key element for our understanding of their broad- band spectra, and their structure and evolution in our local, as well as the high-redshift Universe. The main tool we use for these measurements is the observed luminosity in various spectral lines and/or continuum bands. However, the available star-formation rate (SFR) indicators are often discrepant and subject to physical biases and calibration uncertainties. We are organizing a special session at the 2012 IAU General Assembly in Beijing, China (August 20-31, 2012) in order to bring together theoreticians and observers working in different contexts of star-formation to discuss the status of current SFR indicators, to identify open issues and to define a strategic framework for their resolution. The is an ideal time to synthesize information from the current golden era of space astrophysics and still have influence on the upcoming missions that will broaden our view of star-formation. We will be including high-energy constraints on SFR in the program and encourage participation from the high energy astrophysics community. This poster also includes a full list of Beijing IAU sessions so you can plan your trip!

  1. Star formation rates in isolated galaxies selected from the Two-Micron All-Sky Survey

    NASA Astrophysics Data System (ADS)

    Melnyk, O.; Karachentseva, V.; Karachentsev, I.

    2015-08-01

    We have considered the star formation properties of 1616 isolated galaxies from the 2MASS XSC (Extended Source Catalog) selected sample (2MIG) with the far-ultraviolet GALEX magnitudes. This sample was then compared with corresponding properties of isolated galaxies from the Local Orphan Galaxies (LOG) catalogue and paired galaxies. We found that different selection algorithms define different populations of isolated galaxies. The population of the LOG catalogue, selected from non-clustered galaxies in the Local Supercluster volume, mostly consists of low-mass spiral and late-type galaxies. The specific star formation rate (SSFR) upper limit in isolated and paired galaxies does not exceed the value of ˜dex(-9.4). This is probably common for galaxies of differing activity and environment (at least at z < 0.06). The fractions of quenched galaxies are nearly twice as high in the paired galaxy sample as in the 2MIG isolated galaxy sample. From the behaviour of (S)SFR versus M* relations we deduced that the characteristic value influencing evolutionary processes is the galaxy mass. However, the environmental influence is notable: paired massive galaxies with logM* > 11.5 have higher (S)SFR than isolated galaxies. Our results suggest that the environment helps to trigger the star formation in the highest mass galaxies. We found that the fraction of AGN in the paired sample is only a little higher than in our isolated galaxy sample. We assume that AGN phenomenon is probably defined by secular galaxy evolution.

  2. 40 CFR Table I-12 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for Semiconductor Manufacturing for... (Bijk) for Semiconductor Manufacturing for Use With the Stack Test Method (300 mm and 450 mm...

  3. 40 CFR Table I-11 to Subpart I of... - Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Default Emission Factors (1-Uij) for Gas Utilization Rates (Uij) and By-Product Formation Rates (Bijk) for Semiconductor Manufacturing for... (Bijk) for Semiconductor Manufacturing for Use With the Stack Test Method (150 mm and 200 mm...

  4. An Evolutionary Model for Collapsing Molecular Clouds and their Star Formation Activity. II. Mass Dependence of the Star Formation Rate

    NASA Astrophysics Data System (ADS)

    Zamora-Avilés, Manuel; Vázquez-Semadeni, Enrique

    2014-10-01

    We discuss the evolution and dependence on cloud mass of the star formation rate (SFR) and efficiency (SFE) of star-forming molecular clouds (MCs) within the scenario that clouds are undergoing global collapse and that the SFR is controlled by ionization feedback. We find that low-mass clouds (M max <~ 104 M ⊙) spend most of their evolution at low SFRs, but end their lives with a mini-burst, reaching a peak SFR ~104 M ⊙ Myr-1, although their time-averaged SFR is only langSFRrang ~ 102 M ⊙ Myr-1. The corresponding efficiencies are SFEfinal <~ 60% and langSFErang <~ 1%. For more massive clouds (M max >~ 105 M ⊙), the SFR first increases and then reaches a plateau because the clouds are influenced by stellar feedback since earlier in their evolution. As a function of cloud mass, langSFRrang and langSFErang are well represented by the fits langSFRrang ≈ 100(1 + M max/1.4 × 105 M ⊙)1.68 M ⊙ Myr-1 and langSFErang ≈ 0.03(M max/2.5 × 105 M ⊙)0.33, respectively. Moreover, the SFR of our model clouds follows closely the SFR-dense gas mass relation recently found by Lada et al. during the epoch when their instantaneous SFEs are comparable to those of the clouds considered by those authors. Collectively, a Monte Carlo integration of the model-predicted SFR(M) over a Galactic giant molecular cloud mass spectrum yields values for the total Galactic SFR that are within half an order of magnitude of the relation obtained by Gao & Solomon. Our results support the scenario that star-forming MCs may be in global gravitational collapse and that the low observed values of the SFR and SFE are a result of the interruption of each SF episode, caused primarily by the ionizing feedback from massive stars.

  5. Explaining the Three-decade Correlation between Star Formation Rate and Stellar Mass in Galaxies at z~1

    NASA Astrophysics Data System (ADS)

    Gawiser, Eric J.; Kurczynski, Peter; Acquaviva, Viviana; UVUDF Team, CANDELS Team

    2016-01-01

    In star-forming galaxies across cosmic time, a correlation has been found between the mass of stars already assembled and its time derivative, the star formation rate. This surprising correlation was not predicted by theory, but it can be reproduced within cosmological hydrodynamics simulations and semi-analytical models of galaxy formation. Here we use SpeedyMC, a Markov Chain Monte Carlo code for Spectral Energy Distribution fitting, to measure the star formation rates and stellar masses of 800 galaxies from the Ultraviolet Ultradeep Field (UVUDF) and CANDELS/GOODS-S field at redshift 1 < z < 1.5. This galaxy sample leverages the deepest images taken with the Hubble Space Telescope to extend the SFR-M* correlation a factor of 10-100X lower in M* than previous studies, down to values of 10^7 M_sun comparable to present-day dwarf galaxies. Accounting for each galaxy's parameter uncertainties, including their covariances, yields a power-law correlation across three decades with intrinsic scatter of 0.2 dex. Having assumed realistic star formation histories that can rise and fall with time, we are able to measure star formation rates on timescales varying from instantaneous to the "lifetime" average for each galaxy. As the timescale over which star formation rate is averaged increases, the power-law exponent of the correlation with stellar mass increases to unity, and the scatter decreases to 0.05 dex. We conclude that the observed correlation between star formation rate and stellar mass results from a tight correlation between recent and lifetime-average star formation rates and a narrow spread of galaxy ages at a given star formation rate. The resulting correlation provides crucial evidence that galaxy formation proceeds through self-regulated star formation. We gratefully acknowledge support from NSF grant AST-1055919 and grants from NASA via the Space Telescope Science Institute in support of programs 12060.57, 12445.56, and GO-12534.

  6. Free energy of cluster formation and a new scaling relation for the nucleation rate

    SciTech Connect

    Tanaka, Kyoko K.; Tanaka, Hidekazu; Diemand, Jürg; Angélil, Raymond

    2014-05-21

    Recent very large molecular dynamics simulations of homogeneous nucleation with (1 − 8) × 10{sup 9} Lennard-Jones atoms [J. Diemand, R. Angélil, K. K. Tanaka, and H. Tanaka, J. Chem. Phys. 139, 074309 (2013)] allow us to accurately determine the formation free energy of clusters over a wide range of cluster sizes. This is now possible because such large simulations allow for very precise measurements of the cluster size distribution in the steady state nucleation regime. The peaks of the free energy curves give critical cluster sizes, which agree well with independent estimates based on the nucleation theorem. Using these results, we derive an analytical formula and a new scaling relation for nucleation rates: ln J{sup ′}/η is scaled by ln S/η, where the supersaturation ratio is S, η is the dimensionless surface energy, and J{sup ′} is a dimensionless nucleation rate. This relation can be derived using the free energy of cluster formation at equilibrium which corresponds to the surface energy required to form the vapor-liquid interface. At low temperatures (below the triple point), we find that the surface energy divided by that of the classical nucleation theory does not depend on temperature, which leads to the scaling relation and implies a constant, positive Tolman length equal to half of the mean inter-particle separation in the liquid phase.

  7. Formation and phase transitions of methane hydrates under dynamic loadings: Compression rate dependent kinetics

    NASA Astrophysics Data System (ADS)

    Chen, Jing-Yin; Yoo, Choong-Shik

    2012-03-01

    We describe high-pressure kinetic studies of the formation and phase transitions of methane hydrates (MH) under dynamic loading conditions, using a dynamic-diamond anvil cell (d-DAC) coupled with time-resolved confocal micro-Raman spectroscopy and high-speed microphotography. The time-resolved spectra and dynamic pressure responses exhibit profound compression-rate dependences associated with both the formation and the solid-solid phase transitions of MH-I to II and MH-II to III. Under dynamic loading conditions, MH forms only from super-compressed water and liquid methane in a narrow pressure range between 0.9 and 1.6 GPa at the one-dimensional (1D) growth rate of 42 μm/s. MH-I to II phase transition occurs at the onset of water solidification 0.9 GPa, following a diffusion controlled mechanism. We estimated the activation volume to be -109 ± 29 Å3, primarily associated with relatively slow methane diffusion which follows the rapid interfacial reconstruction, or martensitic displacements of atomic positions and hydrogen bonds, of 51262 water cages in MH-I to 4351263 cages in MH-II. MH-II to III transition, on the other hand, occurs over a broad pressure range between 1.5 and 2.2 GPa, following a reconstructive mechanism from super-compressed MH-II clathrates to a broken ice-filled viscoelastic solid of MH-III. It is found that the profound dynamic effects observed in the MH formation and phase transitions are primarily governed by the stability of water and ice phases at the relevant pressures.

  8. Formation and phase transitions of methane hydrates under dynamic loadings: compression rate dependent kinetics.

    PubMed

    Chen, Jing-Yin; Yoo, Choong-Shik

    2012-03-21

    We describe high-pressure kinetic studies of the formation and phase transitions of methane hydrates (MH) under dynamic loading conditions, using a dynamic-diamond anvil cell (d-DAC) coupled with time-resolved confocal micro-Raman spectroscopy and high-speed microphotography. The time-resolved spectra and dynamic pressure responses exhibit profound compression-rate dependences associated with both the formation and the solid-solid phase transitions of MH-I to II and MH-II to III. Under dynamic loading conditions, MH forms only from super-compressed water and liquid methane in a narrow pressure range between 0.9 and 1.6 GPa at the one-dimensional (1D) growth rate of 42 μm/s. MH-I to II phase transition occurs at the onset of water solidification 0.9 GPa, following a diffusion controlled mechanism. We estimated the activation volume to be -109±29 Å(3), primarily associated with relatively slow methane diffusion which follows the rapid interfacial reconstruction, or martensitic displacements of atomic positions and hydrogen bonds, of 5(12)6(2) water cages in MH-I to 4(3)5(12)6(3) cages in MH-II. MH-II to III transition, on the other hand, occurs over a broad pressure range between 1.5 and 2.2 GPa, following a reconstructive mechanism from super-compressed MH-II clathrates to a broken ice-filled viscoelastic solid of MH-III. It is found that the profound dynamic effects observed in the MH formation and phase transitions are primarily governed by the stability of water and ice phases at the relevant pressures. PMID:22443783

  9. THE MASS-INDEPENDENCE OF SPECIFIC STAR FORMATION RATES IN GALACTIC DISKS

    SciTech Connect

    Abramson, Louis E.; Gladders, Michael D.; Kelson, Daniel D.; Dressler, Alan; Oemler, Augustus Jr.; Poggianti, Bianca; Vulcani, Benedetta

    2014-04-20

    The slope of the star formation rate/stellar mass relation (the SFR {sup M}ain Sequence{sup ;} SFR-M {sub *}) is not quite unity: specific star formation rates (SFR/M {sub *}) are weakly but significantly anti-correlated with M {sub *}. Here we demonstrate that this trend may simply reflect the well-known increase in bulge mass-fractions—portions of a galaxy not forming stars—with M {sub *}. Using a large set of bulge/disk decompositions and SFR estimates derived from the Sloan Digital Sky Survey, we show that re-normalizing SFR by disk stellar mass (sSFR{sub disk} ≡ SFR/M {sub *,} {sub disk}) reduces the M {sub *} dependence of SF efficiency by ∼0.25 dex per dex, erasing it entirely in some subsamples. Quantitatively, we find log sSFR{sub disk}-log M {sub *} to have a slope β{sub disk} in [ – 0.20, 0.00] ± 0.02 (depending on the SFR estimator and Main Sequence definition) for star-forming galaxies with M {sub *} ≥ 10{sup 10} M {sub ☉} and bulge mass-fractions B/T ≲ 0.6, generally consistent with a pure-disk control sample (β{sub control} = –0.05 ± 0.04). That (SFR/M {sub *,} {sub disk}) is (largely) independent of host mass for star-forming disks has strong implications for aspects of galaxy evolution inferred from any SFR-M {sub *} relation, including manifestations of ''mass quenching'' (bulge growth), factors shaping the star-forming stellar mass function (uniform dlog M {sub *}/dt for low-mass, disk-dominated galaxies), and diversity in star formation histories (dispersion in SFR(M {sub *}, t)). Our results emphasize the need to treat galaxies as composite systems—not integrated masses—in observational and theoretical work.

  10. Transient β-hairpin formation in α-synuclein monomer revealed by coarse-grained molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Yu, Hang; Han, Wei; Ma, Wen; Schulten, Klaus

    2015-12-01

    Parkinson's disease, originating from the intrinsically disordered peptide α-synuclein, is a common neurodegenerative disorder that affects more than 5% of the population above age 85. It remains unclear how α-synuclein monomers undergo conformational changes leading to aggregation and formation of fibrils characteristic for the disease. In the present study, we perform molecular dynamics simulations (over 180 μs in aggregated time) using a hybrid-resolution model, Proteins with Atomic details in Coarse-grained Environment (PACE), to characterize in atomic detail structural ensembles of wild type and mutant monomeric α-synuclein in aqueous solution. The simulations reproduce structural properties of α-synuclein characterized in experiments, such as secondary structure content, long-range contacts, chemical shifts, and 3J(HNHCα)-coupling constants. Most notably, the simulations reveal that a short fragment encompassing region 38-53, adjacent to the non-amyloid-β component region, exhibits a high probability of forming a β-hairpin; this fragment, when isolated from the remainder of α-synuclein, fluctuates frequently into its β-hairpin conformation. Two disease-prone mutations, namely, A30P and A53T, significantly accelerate the formation of a β-hairpin in the stated fragment. We conclude that the formation of a β-hairpin in region 38-53 is a key event during α-synuclein aggregation. We predict further that the G47V mutation impedes the formation of a turn in the β-hairpin and slows down β-hairpin formation, thereby retarding α-synuclein aggregation.

  11. Transient β-hairpin formation in α-synuclein monomer revealed by coarse-grained molecular dynamics simulation

    SciTech Connect

    Yu, Hang; Ma, Wen; Han, Wei; Schulten, Klaus

    2015-12-28

    Parkinson’s disease, originating from the intrinsically disordered peptide α-synuclein, is a common neurodegenerative disorder that affects more than 5% of the population above age 85. It remains unclear how α-synuclein monomers undergo conformational changes leading to aggregation and formation of fibrils characteristic for the disease. In the present study, we perform molecular dynamics simulations (over 180 μs in aggregated time) using a hybrid-resolution model, Proteins with Atomic details in Coarse-grained Environment (PACE), to characterize in atomic detail structural ensembles of wild type and mutant monomeric α-synuclein in aqueous solution. The simulations reproduce structural properties of α-synuclein characterized in experiments, such as secondary structure content, long-range contacts, chemical shifts, and {sup 3}J(H{sub N}H{sub C{sub α}})-coupling constants. Most notably, the simulations reveal that a short fragment encompassing region 38-53, adjacent to the non-amyloid-β component region, exhibits a high probability of forming a β-hairpin; this fragment, when isolated from the remainder of α-synuclein, fluctuates frequently into its β-hairpin conformation. Two disease-prone mutations, namely, A30P and A53T, significantly accelerate the formation of a β-hairpin in the stated fragment. We conclude that the formation of a β-hairpin in region 38-53 is a key event during α-synuclein aggregation. We predict further that the G47V mutation impedes the formation of a turn in the β-hairpin and slows down β-hairpin formation, thereby retarding α-synuclein aggregation.

  12. Transcriptome analysis reveals new insight into appressorium formation and function in the rice blast fungus Magnaporthe oryzae

    PubMed Central

    Oh, Yeonyee; Donofrio, Nicole; Pan, Huaqin; Coughlan, Sean; Brown, Douglas E; Meng, Shaowu; Mitchell, Thomas; Dean, Ralph A

    2008-01-01

    Background Rice blast disease is caused by the filamentous Ascomycetous fungus Magnaporthe oryzae and results in significant annual rice yield losses worldwide. Infection by this and many other fungal plant pathogens requires the development of a specialized infection cell called an appressorium. The molecular processes regulating appressorium formation are incompletely understood. Results We analyzed genome-wide gene expression changes during spore germination and appressorium formation on a hydrophobic surface compared to induction by cAMP. During spore germination, 2,154 (approximately 21%) genes showed differential expression, with the majority being up-regulated. During appressorium formation, 357 genes were differentially expressed in response to both stimuli. These genes, which we refer to as appressorium consensus genes, were functionally grouped into Gene Ontology categories. Overall, we found a significant decrease in expression of genes involved in protein synthesis. Conversely, expression of genes associated with protein and amino acid degradation, lipid metabolism, secondary metabolism and cellular transportation exhibited a dramatic increase. We functionally characterized several differentially regulated genes, including a subtilisin protease (SPM1) and a NAD specific glutamate dehydrogenase (Mgd1), by targeted gene disruption. These studies revealed hitherto unknown findings that protein degradation and amino acid metabolism are essential for appressorium formation and subsequent infection. Conclusion We present the first comprehensive genome-wide transcript profile study and functional analysis of infection structure formation by a fungal plant pathogen. Our data provide novel insight into the underlying molecular mechanisms that will directly benefit efforts to identify fungal pathogenicity factors and aid the development of new disease management strategies. PMID:18492280

  13. The structure, dynamics, and star formation rate of the Orion nebula cluster

    SciTech Connect

    Da Rio, Nicola; Tan, Jonathan C.; Jaehnig, Karl

    2014-11-01

    The spatial morphology and dynamical status of a young, still-forming stellar cluster provide valuable clues to the conditions during the star formation event and the processes that regulated it. We analyze the Orion Nebula Cluster (ONC), utilizing the latest censuses of its stellar content and membership estimates over a large wavelength range. We determine the center of mass of the ONC and study the radial dependence of angular substructure. The core appears rounder and smoother than the outskirts, which is consistent with a higher degree of dynamical processing. At larger distances, the departure from circular symmetry is mostly driven by the elongation of the system, with very little additional substructure, indicating a somewhat evolved spatial morphology or an expanding halo. We determine the mass density profile of the cluster, which is well fitted by a power law that is slightly steeper than a singular isothermal sphere. Together with the interstellar medium density, which is estimated from average stellar extinction, the mass content of the ONC is insufficient by a factor ∼1.8 to reproduce the observed velocity dispersion from virialized motions, in agreement with previous assessments that the ONC is moderately supervirial. This may indicate recent gas dispersal. Based on the latest estimates for the age spread in the system and our density profiles, we find that at the half-mass radius, 90% of the stellar population formed within ∼5-8 free-fall times (t {sub ff}). This implies a star formation efficiency per t {sub ff} of ε{sub ff} ∼ 0.04-0.07 (i.e., relatively slow and inefficient star formation rates during star cluster formation).

  14. Hα imaging survey of Wolf-Rayet galaxies: morphologies and star formation rates

    NASA Astrophysics Data System (ADS)

    Jaiswal, S.; Omar, A.

    2016-06-01

    The Hα and optical broadband images of 25 nearby Wolf-Rayet (WR) galaxies are presented. The WR galaxies are known to have the presence of a recent (≤10 Myr) and massive star formation episode. The photometric Hα fluxes are estimated, and corrected for extinction and line contamination in the filter pass-bands. The star formation rates (SFRs) are estimated using Hα images and from the archival data in the far-ultraviolet (FUV), far-infrared (FIR) and 1.4 GHz radio continuum wave-bands. A comparison of SFRs estimated from different wavebands is made after including similar data available in literature for other WR galaxies. The Hα based SFRs are found to be tightly correlated with SFRs estimated from the FUV data. The correlations also exist with SFRs estimates based on the radio and FIR data. The WR galaxies also follow the radio-FIR correlation known for normal star forming galaxies, although it is seen here that majority of dwarf WR galaxies have radio deficiency. An analysis using ratio of non-thermal to thermal radio continuum and ratio of FUV to Hα SFR indicates that WR galaxies have lesser non-thermal radio emission compared to normal galaxies, most likely due to lack of supernova from the very young star formation episode in the WR galaxies. The morphologies of 16 galaxies in our sample are highly suggestive of an ongoing tidal interaction or a past merger in these galaxies. This survey strengthens the conclusions obtained from previous similar studies indicating the importance of tidal interactions in triggering star-formation in WR galaxies.

  15. THE MOSDEF SURVEY: MASS, METALLICITY, AND STAR-FORMATION RATE AT z ∼ 2.3

    SciTech Connect

    Sanders, Ryan L.; Shapley, Alice E.; Kriek, Mariska; Price, Sedona H.; Reddy, Naveen A.; Freeman, William R.; Siana, Brian; Mobasher, Bahram; Shivaei, Irene; De Groot, Laura; Coil, Alison L.

    2015-02-01

    We present results on the z ∼ 2.3 mass-metallicity relation (MZR) using early observations from the MOSFIRE Deep Evolution Field survey. We use an initial sample of 87 star-forming galaxies with spectroscopic coverage of Hβ, [O III] λ5007, Hα, and [N II] λ6584 rest-frame optical emission lines, and estimate the gas-phase oxygen abundance based on the N2 and O3N2 strong-line indicators. We find a positive correlation between stellar mass and metallicity among individual z ∼ 2.3 galaxies using both the N2 and O3N2 indicators. We also measure the emission-line ratios and corresponding oxygen abundances for composite spectra in bins of stellar mass. Among composite spectra, we find a monotonic increase in metallicity with increasing stellar mass, offset ∼0.15-0.3 dex below the local MZR. When the sample is divided at the median star-formation rate (SFR), we do not observe significant SFR dependence of the z ∼ 2.3 MZR among either individual galaxies or composite spectra. We furthermore find that z ∼ 2.3 galaxies have metallicities ∼0.1 dex lower at a given stellar mass and SFR than is observed locally. This offset suggests that high-redshift galaxies do not fall on the local ''fundamental metallicity relation'' among stellar mass, metallicity, and SFR, and may provide evidence of a phase of galaxy growth in which the gas reservoir is built up due to inflow rates that are higher than star-formation and outflow rates. However, robust conclusions regarding the gas-phase oxygen abundances of high-redshift galaxies await a systematic reappraisal of the application of locally calibrated metallicity indicators at high redshift.

  16. GLOBAL STAR FORMATION RATES AND DUST EMISSION OVER THE GALAXY INTERACTION SEQUENCE

    SciTech Connect

    Lanz, Lauranne; Zezas, Andreas; Smith, Howard A.; Ashby, Matthew L. N.; Fazio, Giovanni G.; Hernquist, Lars; Brassington, Nicola; Da Cunha, Elisabete; Hayward, Christopher C.; Jonsson, Patrik

    2013-05-01

    We measured and modeled spectral energy distributions (SEDs) in 28 bands from the ultraviolet to the far-infrared (FIR) for 31 interacting galaxies in 14 systems. The sample is drawn from the Spitzer Interacting Galaxy Survey, which probes a range of galaxy interaction parameters at multiple wavelengths with an emphasis on the infrared bands. The subset presented in this paper consists of all galaxies for which FIR Herschel SPIRE observations are publicly available. Our SEDs combine the Herschel photometry with multi-wavelength data from Spitzer, GALEX, Swift UVOT, and 2MASS. While the shapes of the SEDs are broadly similar across our sample, strongly interacting galaxies typically have more mid-infrared emission relative to their near-infrared and FIR emission than weakly or moderately interacting galaxies. We modeled the full SEDs to derive host galaxy star formation rates (SFRs), specific star formation rates (sSFRs), stellar masses, dust temperatures, dust luminosities, and dust masses. We find increases in the dust luminosity and mass, SFR, and cold (15-25 K) dust temperature as the interaction progresses from moderately to strongly interacting and between non-interacting and strongly interacting galaxies. We also find increases in the SFR between weakly and strongly interacting galaxies. In contrast, the sSFR remains unchanged across all the interaction stages. The ultraviolet photometry is crucial for constraining the age of the stellar population and the SFR, while dust mass is primarily determined by SPIRE photometry. The SFR derived from the SED modeling agrees well with rates estimated by proportionality relations that depend on infrared emission.

  17. Ionosphere influence on success rate of GPS ambiguity resolution in a satellite formation flying

    NASA Astrophysics Data System (ADS)

    Baroni, Leandro

    2015-10-01

    Satellite formation flying is one of the most promising technologies for future space missions. The distribution of sensors and payloads among different satellites provides more redundancy, flexibility, improved communication coverage, among other advantages. One of the fundamental issues in spacecraft formation flying is precise position and velocity determination between satellites. For missions in low Earth orbits, GPS system can meet the precision requirement in relative positioning, since the satellite dynamics is modeled properly. The key for high accuracy GPS relative positioning is to resolve the ambiguities to their integer values. Ambiguities resolved successfully can improve the positioning accuracy to decimetre or even millimetre-level. So, integer carrier phase ambiguity resolution is often a prerequisite for high precision GPS positioning. The determination of relative position was made using an extended Kalman filter. The filter must take into account imperfections in dynamic modeling of perturbations affecting the orbital flight, and changes in solar activity that affects the GPS signal propagation, for mitigating these effects on relative positioning accuracy. Thus, this work aims to evaluate the impact of ionosphere variation, caused by changes in solar activity, in success rate of ambiguity resolution. Using the Ambiguity Dilution of Precision (ADOP) concept, the ambiguity success rate is analyzed and the expected precision of the ambiguity-fixed solution is calculated. Evaluations were performed using actual data from GRACE mission and analyzed for their performance in real scenarios. Analyses were conducted in different configurations of relative position and during different levels of solar activity. Results bring the impact of various disturbances and modeling of solar activity level on the success rate of ambiguity resolution.

  18. Negative Ion Photoelectron Spectroscopy Reveals Thermodynamic Advantage of Organic Acids in Facilitating Formation of Bisulfate Ion Clusters: Atmospheric Implications

    SciTech Connect

    Hou, Gao-Lei; Lin, Wei; Deng, Shihu; Zhang, Jian; Zheng, Weijun; Paesani, Francesco; Wang, Xue B.

    2013-03-07

    Recent lab and field measurements have indicated critical roles of organic acids in enhancing new atmospheric aerosol formation. Such findings have stimulated theoretical studies with the aim of understanding interaction of organic acids with common aerosol nucleation precursors like bisulfate (HSO4-). In this Letter, we report a combined negative ion photoelectron spectroscopic and theoretical investigation of molecular clusters formed by HSO4- with succinic acid (SUA, HO2C(CH2)2CO2H), HSO4-(SUA)n (n = 0-2), along with HSO4-(H2O)n and HSO4-(H2SO4)n. It is found that one SUA molecule can stabilize HSO4- by ca. 39 kcal/mol, triple the corresponding value that one water molecule is capable of (ca. 13 kcal/mol). Molecular dynamics simulations and quantum chemical calculations reveal the most plausible structures of these clusters and attribute the stability of these clusters due to formation of strong hydrogen bonds. This work provides direct experimental evidence showing significant thermodynamic advantage by involving organic acid molecules to promote formation and growth in bisulfate clusters and aerosols.

  19. STAR FORMATION RATES IN RESOLVED GALAXIES: CALIBRATIONS WITH NEAR- AND FAR-INFRARED DATA FOR NGC 5055 AND NGC 6946

    SciTech Connect

    Li Yiming; Crocker, Alison F.; Calzetti, Daniela; Wilson, Christine D.; Kennicutt, Robert C.; Galametz, M.; Murphy, Eric J.; Brandl, Bernhard R.; Groves, B.; Draine, B. T.; Johnson, B. D.; Armus, L.; Gordon, K. D.; Croxall, K.; Dale, D. A.; Engelbracht, C. W.; Hinz, J.; Hao, C.-N.; Helou, G.; Hunt, L. K.; and others

    2013-05-10

    We use the near-infrared Br{gamma} hydrogen recombination line as a reference star formation rate (SFR) indicator to test the validity and establish the calibration of the Herschel/PACS 70 {mu}m emission as a SFR tracer for sub-galactic regions in external galaxies. Br{gamma} offers the double advantage of directly tracing ionizing photons and of being relatively insensitive to the effects of dust attenuation. For our first experiment, we use archival Canada-France-Hawaii Telescope Br{gamma} and Ks images of two nearby galaxies: NGC 5055 and NGC 6946, which are also part of the Herschel program KINGFISH (Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel). We use the extinction corrected Br{gamma} emission to derive the SFR(70) calibration for H II regions in these two galaxies. A comparison of the SFR(70) calibrations at different spatial scales, from 200 pc to the size of the whole galaxy, reveals that about 50% of the total 70 {mu}m emission is due to dust heated by stellar populations that are unrelated to the current star formation. We use a simple model to qualitatively relate the increase of the SFR(70) calibration coefficient with decreasing region size to the star formation timescale. We provide a calibration for an unbiased SFR indicator that combines the observed H{alpha} with the 70 {mu}m emission, also for use in H II regions. We briefly analyze the PACS 100 and 160 {mu}m maps and find that longer wavelengths are not as good SFR indicators as 70 {mu}m, in agreement with previous results. We find that the calibrations show about 50% difference between the two galaxies, possibly due to effects of inclination.

  20. Peroxidase-catalyzed oxidative coupling of phenols in the presence of geosorbents: rates of non-extractable product formation.

    PubMed

    Huang, Qingguo; Selig, Hildegarde; Weber, Walter J

    2002-02-15

    Oxidative coupling processes in subsurface systems comprise a form of natural contaminant attenuation in which hydroxylated aromatic compounds (HACs) are incorporated into soil/sediment organic matter matrices. Here we describe the oxidative coupling of phenol catalyzed by horseradish peroxidase (HRP) in systems containing two geosorbents having organic matter of different composition; specifically Chelsea soil, a near-surface geologically young soil having a predominantly humic-type soil/sediment organic matter (SOM) matrix, and Lachine shale, a diagenetically older natural material having a predominantly kerogen-type SOM matrix. It was found that each of these two different types of natural geosorbents increased the formation of non-extractable coupling products (NEPs) over that which occurred in solids-free systems. The extent of coupling was higher in the systems containing humic-type Chelsea SOM than in those containing kerogen-type Lachine SOM. It was observed that HRP inactivation by free radical attack was significantly reduced in the presence of each geosorbent. A rate model was developed to facilitate quantitative evaluation and mechanistic interpretation of such coupling processes. Experimental rate measurements revealed thatthe greater extent of reaction observed in the presence of Chelsea soil than in the presence of Lachine shale can be attributed to two factors: (i) more effective protection of HRP from inactivation by the Chelsea SOM and (ii) the greater reactivity of Chelsea SOM with respect to cross-coupling. Interrelationships among enzyme protection, cross-coupling reactivity, and SOM chemistry are discussed. PMID:11878372

  1. An evolutionary model for collapsing molecular clouds and their star formation activity. II. Mass dependence of the star formation rate

    SciTech Connect

    Zamora-Avilés, Manuel; Vázquez-Semadeni, Enrique

    2014-10-01

    We discuss the evolution and dependence on cloud mass of the star formation rate (SFR) and efficiency (SFE) of star-forming molecular clouds (MCs) within the scenario that clouds are undergoing global collapse and that the SFR is controlled by ionization feedback. We find that low-mass clouds (M {sub max} ≲ 10{sup 4} M {sub ☉}) spend most of their evolution at low SFRs, but end their lives with a mini-burst, reaching a peak SFR ∼10{sup 4} M {sub ☉} Myr{sup –1}, although their time-averaged SFR is only (SFR) ∼ 10{sup 2} M {sub ☉} Myr{sup –1}. The corresponding efficiencies are SFE{sub final} ≲ 60% and (SFE) ≲ 1%. For more massive clouds (M {sub max} ≳ 10{sup 5} M {sub ☉}), the SFR first increases and then reaches a plateau because the clouds are influenced by stellar feedback since earlier in their evolution. As a function of cloud mass, (SFR) and (SFE) are well represented by the fits (SFR) ≈ 100(1 + M {sub max}/1.4 × 10{sup 5} M {sub ☉}){sup 1.68} M {sub ☉} Myr{sup –1} and (SFE) ≈ 0.03(M {sub max}/2.5 × 10{sup 5} M {sub ☉}){sup 0.33}, respectively. Moreover, the SFR of our model clouds follows closely the SFR-dense gas mass relation recently found by Lada et al. during the epoch when their instantaneous SFEs are comparable to those of the clouds considered by those authors. Collectively, a Monte Carlo integration of the model-predicted SFR(M) over a Galactic giant molecular cloud mass spectrum yields values for the total Galactic SFR that are within half an order of magnitude of the relation obtained by Gao and Solomon. Our results support the scenario that star-forming MCs may be in global gravitational collapse and that the low observed values of the SFR and SFE are a result of the interruption of each SF episode, caused primarily by the ionizing feedback from massive stars.

  2. Dissolution Rate Enhancement of Clarithromycin Using Ternary Ground Mixtures: Nanocrystal Formation

    PubMed Central

    Shahbaziniaz, Malihe; Foroutan, Seyed Mohsen; Bolourchian, Noushin

    2013-01-01

    Clarithromycin (CLA), a broad-spectrum macrolide, is a poorly soluble drug with dissolution rate limited absorption. The aim of this investigation was to prepare CLA nanoparticles from a ternary ground mixture in the presence of sodium lauryl sulfate (SLS) and polyvinyl pyrrolidone (PVP) as co-grinding water-soluble compounds, in order to improve the drug dissolution rate. Different weight ratios of CLA: SLS: PVP were ground in a dry process by planetary ball mill using different grinding ball size. Following the dissolution rate study, physical properties of the best dissolved co-ground formulation was studied. The accelerated stability studies were also conducted on the co-ground formulation. The results revealed that the dissolution rate of ternary ground mixtures was much higher than that of the intact drug (p < 0.001). Decreasing the grinding ball size and weight with the same rotation speed resulted in particles with decreased dissolution. On the other hand, increasing the PVP concentration in the formulations reduced the drug dissolution. Dissolution efficiencies (DE10 and DE30) for the best dissolved formulation, which consisted of the equal ratio of each co-ground component, were 8.7 and 5 folds higher than the untreated CLA, respectively. This formulation formed nanocrystals with enhanced solubility after dispersing in water. X-ray diffraction, differential scanning calorimetry and infrared spectrophotometry confirmed no chemical interaction and phase transition during the process. Accelerated stability studies confirmed that the co-ground mixture almost remained unchanged in terms of dissolution rate, drug assay and particle size after exposing in stability conditions for three months. PMID:24523739

  3. Dissolution rate enhancement of clarithromycin using ternary ground mixtures: nanocrystal formation.

    PubMed

    Shahbaziniaz, Malihe; Foroutan, Seyed Mohsen; Bolourchian, Noushin

    2013-01-01

    Clarithromycin (CLA), a broad-spectrum macrolide, is a poorly soluble drug with dissolution rate limited absorption. The aim of this investigation was to prepare CLA nanoparticles from a ternary ground mixture in the presence of sodium lauryl sulfate (SLS) and polyvinyl pyrrolidone (PVP) as co-grinding water-soluble compounds, in order to improve the drug dissolution rate. Different weight ratios of CLA: SLS: PVP were ground in a dry process by planetary ball mill using different grinding ball size. Following the dissolution rate study, physical properties of the best dissolved co-ground formulation was studied. The accelerated stability studies were also conducted on the co-ground formulation. The results revealed that the dissolution rate of ternary ground mixtures was much higher than that of the intact drug (p < 0.001). Decreasing the grinding ball size and weight with the same rotation speed resulted in particles with decreased dissolution. On the other hand, increasing the PVP concentration in the formulations reduced the drug dissolution. Dissolution efficiencies (DE10 and DE30) for the best dissolved formulation, which consisted of the equal ratio of each co-ground component, were 8.7 and 5 folds higher than the untreated CLA, respectively. This formulation formed nanocrystals with enhanced solubility after dispersing in water. X-ray diffraction, differential scanning calorimetry and infrared spectrophotometry confirmed no chemical interaction and phase transition during the process. Accelerated stability studies confirmed that the co-ground mixture almost remained unchanged in terms of dissolution rate, drug assay and particle size after exposing in stability conditions for three months. PMID:24523739

  4. Rate of F center formation in sapphire under low-energy low-fluence Ar+ irradiation

    NASA Astrophysics Data System (ADS)

    Epie, E. N.; Wijesundera, D. N.; Tilakaratne, B. P.; Chen, Q. Y.; Chu, W. K.

    2016-03-01

    Ionoluminescence, optical absorption spectroscopy and Rutherford backscattering spectrometry channelling (RBS-C) have been used to study the rate of F center formation with fluence in 170 keV Ar+ irradiated single crystals of α-Al2O3 (sapphire) at room temperature. Implantation fluences range between 1013 cm-2 and 5 ×1014 cm-2. F center density (NF) has been found to display an initial rapid linear increase with Ar+ fluence followed by saturation to a maximum value of 1.74 ×1015 cm-2. Experimental results show a 1-1 correlation between radiation damage in the oxygen sublattice and F center density. This suggest F center kinetics in sapphire under low-energy low-fluence Ar irradiation is a direct consequence of dynamic competition between oxygen defect creation and recombination. An attempt has also been made to extend this discussion to F center kinetics in sapphire under swift heavy ion irradiation.

  5. Nature or nurture? Clues from the distribution of specific star formation rates in SDSS galaxies

    NASA Astrophysics Data System (ADS)

    Casado, J.; Ascasibar, Y.; Gavilán, M.; Terlevich, R.; Terlevich, E.; Hoyos, C.; Díaz, A. I.

    2015-07-01

    This work investigates the main mechanism(s) that regulate the specific star formation rate (SSFR) in nearby galaxies, cross-correlating two proxies of this quantity - the equivalent width of the Hα line and the (u - r) colour - with other physical properties (mass, metallicity, environment, morphology, and the presence of close companions) in a sample of ˜82 500 galaxies extracted from the Sloan Digital Sky Survey. The existence of a relatively tight `ageing sequence' in the colour-equivalent width plane favours a scenario where the secular conversion of gas into stars (i.e. nature) is the main physical driver of the instantaneous SSFR and the gradual transition from a `chemically primitive' (metal-poor and intensely star-forming) state to a `chemically evolved' (metal-rich and passively evolving) system. Nevertheless, environmental factors (i.e. nurture) are also important. In the field, galaxies may be temporarily affected by discrete `quenching' and `rejuvenation' episodes, but such events show little statistical significance in a probabilistic sense, and we find no evidence that galaxy interactions are, on average, a dominant driver of star formation. Although visually classified mergers tend to display systematically higher EW(Hα) and bluer (u - r) colours for a given luminosity, most galaxies with high SSFR have uncertain morphologies, which could be due to either internal or external processes. Field galaxies of early and late morphological types are consistent with the gradual `ageing' scenario, with no obvious signatures of a sudden decrease in their SSFR. In contrast, star formation is significantly reduced and sometimes completely quenched on a short time-scale in dense environments, where many objects are found on a `quenched sequence' in the colour-equivalent width plane.

  6. The formation of linear aggregates in magnetic hyperthermia: implications on specific absorption rate and magnetic anisotropy.

    PubMed

    Saville, Steven L; Qi, Bin; Baker, Jonathon; Stone, Roland; Camley, Robert E; Livesey, Karen L; Ye, Longfei; Crawford, Thomas M; Mefford, O Thompson

    2014-06-15

    The design and application of magnetic nanoparticles for use as magnetic hyperthermia agents has garnered increasing interest over the past several years. When designing these systems, the fundamentals of particle design play a key role in the observed specific absorption rate (SAR). This includes the particle's core size, polymer brush length, and colloidal arrangement. While the role of particle core size on the observed SAR has been significantly reported, the role of the polymer brush length has not attracted as much attention. It has recently been reported that for some suspensions linear aggregates form in the presence of an applied external magnetic field, i.e. chains of magnetic particles. The formation of these chains may have the potential for a dramatic impact on the biomedical application of these materials, specifically the efficiency of the particles to transfer magnetic energy to the surrounding cells. In this study we demonstrate the dependence of SAR on magnetite nanoparticle core size and brush length as well as observe the formation of magnetically induced colloidal arrangements. Colloidally stable magnetic nanoparticles were demonstrated to form linear aggregates in an alternating magnetic field. The length and distribution of the aggregates were dependent upon the stabilizing polymer molecular weight. As the molecular weight of the stabilizing layer increased, the magnetic interparticle interactions decreased therefore limiting chain formation. In addition, theoretical calculations demonstrated that interparticle spacing has a significant impact on the magnetic behavior of these materials. This work has several implications for the design of nanoparticle and magnetic hyperthermia systems, while improving understanding of how colloidal arrangement affects SAR. PMID:24767510

  7. Physical origin of the large-scale conformity in the specific star formation rates of galaxies

    NASA Astrophysics Data System (ADS)

    Kauffmann, Guinevere

    2015-12-01

    Two explanations have been put forward to explain the observed conformity between the colours and specific star formation rates (SFR/M*) of galaxies on large scales: (1) the formation times of their surrounding dark matter haloes are correlated (commonly referred to as `assembly bias'), (2) gas is heated over large scales at early times, leading to coherent modulation of cooling and star formation between well-separated galaxies (commonly referred to as `pre-heating'). To distinguish between the pre-heating and assembly bias scenarios, we search for relics of energetic feedback events in the neighbourhood of central galaxies with different specific SFRs. We find a significant excess of very high mass (log M* > 11.3) galaxies out to a distance of 2.5 Mpc around low SFR/M* central galaxies compared to control samples of higher SFR/M* central galaxies with the same stellar mass and redshift. We also find that very massive galaxies in the neighbourhood of low-SFR/M* galaxies have much higher probability of hosting radio-loud active galactic nuclei (AGN). The radio-loud AGN fraction in neighbours with log M* > 11.3 is four times higher around passive, non star-forming centrals at projected distances of 1 Mpc and two times higher at projected distances of 4 Mpc. Finally, we carry out an investigation of conformity effects in the recently publicly released Illustris cosmological hydrodynamical simulation, which includes energetic input both from quasars and from radio mode accretion on to black holes. We do not find conformity effects of comparable amplitude on large scales in the simulations and we propose that gas needs to be pushed out of dark matter haloes more efficiently at high redshifts.

  8. Predicting galaxy star formation rates via the co-evolution of galaxies and haloes

    NASA Astrophysics Data System (ADS)

    Watson, Douglas F.; Hearin, Andrew P.; Berlind, Andreas A.; Becker, Matthew R.; Behroozi, Peter S.; Skibba, Ramin A.; Reyes, Reinabelle; Zentner, Andrew R.; van den Bosch, Frank C.

    2015-01-01

    In this paper, we test the age matching hypothesis that the star formation rate (SFR) of a galaxy of fixed stellar mass is determined by its dark matter halo formation history, e.g. more quiescent galaxies reside in older haloes. We present new Sloan Digital Sky Survey measurements of the galaxy two-point correlation function and galaxy-galaxy lensing as a function of stellar mass and SFR, separated into quenched and star-forming galaxy samples to test this simple model. We find that our age matching model is in excellent agreement with these new measurements. We also find that our model is able to predict: (1) the relative SFRs of central and satellite galaxies, (2) the SFR dependence of the radial distribution of satellite galaxy populations within galaxy groups, rich groups, and clusters and their surrounding larger scale environments, and (3) the interesting feature that the satellite quenched fraction as a function of projected radial distance from the central galaxy exhibits an ˜r-.15 slope, independent of environment. These accurate predictions are intriguing given that we do not explicitly model satellite-specific processes after infall, and that in our model the virial radius does not mark a special transition region in the evolution of a satellite. The success of the model suggests that present-day galaxy SFR is strongly correlated with halo mass assembly history.

  9. Evolution of Galaxies and the Star Formation Rate in the Infrared

    NASA Technical Reports Server (NTRS)

    Pahre, Michael A.; Oliversen, Ronald J. (Technical Monitor)

    2005-01-01

    A central goal of extragalactic observational astronomy is to understand how normal galaxies evolve with redshift, and particularly when galaxies formed their stars. While optical and rest-frame UV observations have begun to address these issues, the interpretation of such data is particularly challenging because of the sensitivity to dust obscuration (at optical and UV wavelengths). The absorbed light is re-radiated at IR wavelengths, hence the optimal indicators of the star formation rate (SFR) is at a rest-frame wavelength of approx. 60 microns. The Spitzer Space Telescope mission is revolutionizing the study of the global properties and evolution of galaxies. Spitzer reaches nearly two orders of magnitude more sensitivity than previous IR space missions. This research program is to study the SFR using statistical samples of galaxies in the local universe, at intermediate redshifts, and set the stage for continuing studies up to z=5. The overall research program is divided into three main investigations: A Mid-IR Hubble Atlas and SFR estimators in the local universe, Evolution of the SFR at 0 < z < 1 using pencil beam redshift surveys, and Galaxy formation and evolution at 1 < z < 5. The first papers from Spitzer were published during the last year, including ten refereed journal papers where the PI was first or co-author.

  10. Rate of Pu(IV) polymer formation in nitric acid solutions. A parametric study

    SciTech Connect

    Toth, L.M.; Osborne, M.M.

    1984-07-01

    The kinetics of Pu(IV) polymer formation has been examined with the intent of developing a simple mathematical equation that would predict the appearance of polymer. The fundamental polymerization rate has been found to be dependent on [Pu(IV)]{sup 1} {sup 2} and [HNO{sub 3}]{sup -6}. The activation energy for polymer formation is real temperature dependent, varying from 66.9 kJ/mol (16 kcal/mol) at 25{sup 0}C to 150.5 kJ/mol (36 kcal/mol) at 105{sup 0}C. These relationships have guided the developement of an empirical model that gives time to form 2% polymer in hours, t = [Pu/sub T/]/sup a/[HNO{sub 3}]/sup b/ Ae/sup c/T/, where a = -1.6, b = 4.6, c = 12.300 K, and A = 7.66 x 10{sup -16} h M{sup -3}; [Pu/sub T/] is the total plutonium concentration, mol/L; and [HNO{sub 3}] is the makeup nitric acid concentration, mol/L. 11 references, 26 figures, 1 table.

  11. THE OBSERVED RELATION BETWEEN STELLAR MASS, DUST EXTINCTION, AND STAR FORMATION RATE IN LOCAL GALAXIES

    SciTech Connect

    Zahid, H. J.; Kewley, L. J.; Kudritzki, R. P.; Yates, R. M.

    2013-02-15

    In this study, we investigate the relation between stellar mass, dust extinction, and star formation rate (SFR) using {approx}150,000 star-forming galaxies from SDSS DR7. We show that the relation between dust extinction and SFR changes with stellar mass. For galaxies at the same stellar mass, dust extinction is anti-correlated with the SFR at stellar masses <10{sup 10} M {sub Sun }. There is a sharp transition in the relation at a stellar mass of 10{sup 10} M {sub Sun }. At larger stellar masses, dust extinction is positively correlated with the SFR for galaxies at the same stellar mass. The observed relation between stellar mass, dust extinction, and SFR presented in this study helps to confirm similar trends observed in the relation between stellar mass, metallicity, and SFR. The relation reported in this study provides important new constraints on the physical processes governing the chemical evolution of galaxies. The correlation between SFR and dust extinction for galaxies with stellar masses >10{sup 10} M {sub Sun} is shown to extend to the population of quiescent galaxies suggesting that the physical processes responsible for the observed relation between stellar mass, dust extinction, and SFR may be related to the processes leading to the shutdown of star formation in galaxies.

  12. Reassessing the Relation Between Stellar Mass, Metallicity, and Star Formation Rate in the Local Universe

    NASA Astrophysics Data System (ADS)

    Telford, Olivia Grace; Dalcanton, Julianne; Skillman, Evan D.; Conroy, Charlie

    2015-01-01

    There is considerable evidence that the well-established mass-metallicity relation in galaxies depends on a third parameter: star formation rate (SFR). The observed strength of this dependence varies substantially depending on the choice of metallicity calibration, but has significant implications for theories of galaxy evolution, as it constrains the interplay between infall of pristine gas, metal production due to star formation, and ejection of enriched gas from galaxies. We present a new analysis of the relation between stellar mass, gas phase metallicity and SFR for ~140,000 star-forming galaxies in the Sloan Digital Sky Survey. Using a new set of theoretically calibrated abundance diagnostics from Dopita et al. (2013), we find a weaker dependence of metallicity on SFR at fixed stellar mass than was found by previous studies using different calibration techniques for gas phase metallicity. We analyze possible biases in the derivation of mass, metallicity, and SFR that could cause the observed strength of the metallicity dependence on SFR to differ from reality, as the calculation of each of these quantities is subject to systematic errors. Chemical evolution models must carefully consider these sources of potential bias when accounting for metallicity dependence on SFR.

  13. Hot spring siliceous stromatolites from Yellowstone National Park: assessing growth rate and laminae formation.

    PubMed

    Berelson, W M; Corsetti, F A; Pepe-Ranney, C; Hammond, D E; Beaumont, W; Spear, J R

    2011-09-01

    Stromatolites are commonly interpreted as evidence of ancient microbial life, yet stromatolite morphogenesis is poorly understood. We apply radiometric tracer and dating techniques, molecular analyses and growth experiments to investigate siliceous stromatolite morphogenesis in Obsidian Pool Prime (OPP), a hot spring in Yellowstone National Park. We examine rates of stromatolite growth and the environmental and/or biologic conditions that affect lamination formation and preservation, both difficult features to constrain in ancient examples. The "main body" of the stromatolite is composed of finely laminated, porous, light-dark couplets of erect (surface normal) and reclining (surface parallel) silicified filamentous bacteria, interrupted by a less-distinct, well-cemented "drape" lamination. Results from dating studies indicate a growth rate of 1-5 cm year(-1) ; however, growth is punctuated. (14)C as a tracer demonstrates that stromatolite cyanobacterial communities fix CO(2) derived from two sources, vent water (radiocarbon dead) and the atmosphere (modern (14)C). The drape facies contained a greater proportion of atmospheric CO(2) and more robust silica cementation (vs. the main body facies), which we interpret as formation when spring level was lower. Systematic changes in lamination style are likely related to environmental forcing and larger scale features (tectonic, climatic). Although the OPP stromatolites are composed of silica and most ancient forms are carbonate, their fine lamination texture requires early lithification. Without early lithification, whether silica or carbonate, it is unlikely that a finely laminated structure representing an ancient microbial mat would be preserved. In OPP, lithification on the nearly diurnal time scale is likely related to temperature control on silica solubility. PMID:21777367

  14. Does the CO-to-H2 conversion factor depend on the star formation rate?

    NASA Astrophysics Data System (ADS)

    Clark, Paul C.; Glover, Simon C. O.

    2015-09-01

    We present a series of numerical simulations that explore how the `X-factor', XCO - the conversion factor between the observed integrated CO emission and the column density of molecular hydrogen - varies with the environmental conditions in which a molecular cloud is placed. Our investigation is centred around two environmental conditions in particular: the cosmic ray ionization rate (CRIR) and the strength of the interstellar radiation field (ISRF). Since both these properties of the interstellar medium (ISM) have their origins in massive stars, we make the assumption in this paper that both the strength of the ISRF and the CRIR scale linearly with the local star formation rate (SFR). The cloud modelling in this study first involves running numerical simulations that capture the cloud dynamics, as well as the time-dependent chemistry, and ISM heating and cooling. These simulations are then post-processed with a line radiative transfer code to create synthetic 12CO (1-0) emission maps from which XCO can be calculated. We find that for 104 M⊙ virialized clouds with mean density 100 cm- 3, XCO is only weakly dependent on the local SFR, varying by a factor of a few over 2 orders of magnitude in SFR. In contrast, we find that for similar clouds but with masses of 105 M⊙, the X-factor will vary by an order of magnitude over the same range in SFR, implying that extragalactic star formation laws should be viewed with caution. However, for denser (104 cm- 3), supervirial clouds such as those found at the centre of the Milky Way, the X-factor is once again independent of the local SFR.

  15. ANALYTICAL THEORY FOR THE INITIAL MASS FUNCTION. III. TIME DEPENDENCE AND STAR FORMATION RATE

    SciTech Connect

    Hennebelle, Patrick

    2013-06-20

    The present paper extends our previous theory of the stellar initial mass function (IMF) by including time dependence and by including the impact of the magnetic field. The predicted mass spectra are similar to the time-independent ones with slightly shallower slopes at large masses and peak locations shifted toward smaller masses by a factor of a few. Assuming that star-forming clumps follow Larson-type relations, we obtain core mass functions in good agreement with the observationally derived IMF, in particular, when taking into account the thermodynamics of the gas. The time-dependent theory directly yields an analytical expression for the star formation rate (SFR) at cloud scales. The SFR values agree well with the observational determinations of various Galactic molecular clouds. Furthermore, we show that the SFR does not simply depend linearly on density, as is sometimes claimed in the literature, but also depends strongly on the clump mass/size, which yields the observed scatter. We stress, however, that any SFR theory depends, explicitly or implicitly, on very uncertain assumptions like clump boundaries or the mass of the most massive stars that can form in a given clump, making the final determinations uncertain by a factor of a few. Finally, we derive a fully time dependent model for the IMF by considering a clump, or a distribution of clumps accreting at a constant rate and thus whose physical properties evolve with time. In spite of its simplicity, this model reproduces reasonably well various features observed in numerical simulations of converging flows. Based on this general theory, we present a paradigm for star formation and the IMF.

  16. Exploring Systematic Effects in the Relation Between Stellar Mass, Gas Phase Metallicity, and Star Formation Rate

    NASA Astrophysics Data System (ADS)

    Telford, O. Grace; Dalcanton, Julianne J.; Skillman, Evan D.; Conroy, Charlie

    2016-08-01

    There is evidence that the well-established mass–metallicity relation in galaxies is correlated with a third parameter: star formation rate (SFR). The strength of this correlation may be used to disentangle the relative importance of different physical processes (e.g., infall of pristine gas, metal-enriched outflows) in governing chemical evolution. However, all three parameters are susceptible to biases that might affect the observed strength of the relation between them. We analyze possible sources of systematic error, including sample bias, application of signal-to-noise ratio cuts on emission lines, choice of metallicity calibration, uncertainty in stellar mass determination, aperture effects, and dust. We present the first analysis of the relation between stellar mass, gas phase metallicity, and SFR using strong line abundance diagnostics from Dopita et al. for ∼130,000 star-forming galaxies in the Sloan Digital Sky Survey and provide a detailed comparison of these diagnostics in an appendix. Using these new abundance diagnostics yields a 30%–55% weaker anti-correlation between metallicity and SFR at fixed stellar mass than that reported by Mannucci et al. We find that, for all abundance diagnostics, the anti-correlation with SFR is stronger for the relatively few galaxies whose current SFRs are elevated above their past average SFRs. This is also true for the new abundance diagnostic of Dopita et al., which gives anti-correlation between Z and SFR only in the high specific star formation rate (sSFR) regime, in contrast to the recent results of Kashino et al. The poorly constrained strength of the relation between stellar mass, metallicity, and SFR must be carefully accounted for in theoretical studies of chemical evolution.

  17. Imbalance of heterologous protein folding and disulfide bond formation rates yields runaway oxidative stress

    PubMed Central

    2012-01-01

    Background The protein secretory pathway must process a wide assortment of native proteins for eukaryotic cells to function. As well, recombinant protein secretion is used extensively to produce many biologics and industrial enzymes. Therefore, secretory pathway dysfunction can be highly detrimental to the cell and can drastically inhibit product titers in biochemical production. Because the secretory pathway is a highly-integrated, multi-organelle system, dysfunction can happen at many levels and dissecting the root cause can be challenging. In this study, we apply a systems biology approach to analyze secretory pathway dysfunctions resulting from heterologous production of a small protein (insulin precursor) or a larger protein (α-amylase). Results HAC1-dependent and independent dysfunctions and cellular responses were apparent across multiple datasets. In particular, processes involving (a) degradation of protein/recycling amino acids, (b) overall transcription/translation repression, and (c) oxidative stress were broadly associated with secretory stress. Conclusions Apparent runaway oxidative stress due to radical production observed here and elsewhere can be explained by a futile cycle of disulfide formation and breaking that consumes reduced glutathione and produces reactive oxygen species. The futile cycle is dominating when protein folding rates are low relative to disulfide bond formation rates. While not strictly conclusive with the present data, this insight does provide a molecular interpretation to an, until now, largely empirical understanding of optimizing heterologous protein secretion. This molecular insight has direct implications on engineering a broad range of recombinant proteins for secretion and provides potential hypotheses for the root causes of several secretory-associated diseases. PMID:22380681

  18. Crystal Structure of the Core Region of Hantavirus Nucleocapsid Protein Reveals the Mechanism for Ribonucleoprotein Complex Formation

    PubMed Central

    Guo, Yu; Wang, Wenming; Sun, Yuna; Ma, Chao; Wang, Xu; Wang, Xin; Liu, Pi; Shen, Shu; Li, Baobin; Lin, Jianping; Deng, Fei

    2015-01-01

    ABSTRACT Hantaviruses, which belong to the genus Hantavirus in the family Bunyaviridae, infect mammals, including humans, causing either hemorrhagic fever with renal syndrome (HFRS) or hantavirus cardiopulmonary syndrome (HCPS) in humans with high mortality. Hantavirus encodes a nucleocapsid protein (NP) to encapsidate the genome and form a ribonucleoprotein complex (RNP) together with viral polymerase. Here, we report the crystal structure of the core domains of NP (NPcore) encoded by Sin Nombre virus (SNV) and Andes virus (ANDV), which are two representative members that cause HCPS in the New World. The constructs of SNV and ANDV NPcore exclude the N- and C-terminal portions of full polypeptide to obtain stable proteins for crystallographic study. The structure features an N lobe and a C lobe to clamp RNA-binding crevice and exhibits two protruding extensions in both lobes. The positively charged residues located in the RNA-binding crevice play a key role in RNA binding and virus replication. We further demonstrated that the C-terminal helix and the linker region connecting the N-terminal coiled-coil domain and NPcore are essential for hantavirus NP oligomerization through contacts made with two adjacent protomers. Moreover, electron microscopy (EM) visualization of native RNPs extracted from the virions revealed that a monomer-sized NP-RNA complex is the building block of viral RNP. This work provides insight into the formation of hantavirus RNP and provides an understanding of the evolutionary connections that exist among bunyaviruses. IMPORTANCE Hantaviruses are distributed across a wide and increasing range of host reservoirs throughout the world. In particular, hantaviruses can be transmitted via aerosols of rodent excreta to humans or from human to human and cause HFRS and HCPS, with mortalities of 15% and 50%, respectively. Hantavirus is therefore listed as a category C pathogen. Hantavirus encodes an NP that plays essential roles both in RNP formation and

  19. Formation Rates of Black Hole Accretion Disk Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Fryer, Chris L.; Woosley, S. E.; Hartmann, Dieter H.

    1999-11-01

    The cosmological origin of at least an appreciable fraction of classical gamma-ray bursts (GRBs) is now supported by redshift measurements for a half-dozen faint host galaxies. Still, the nature of the central engine (or engines) that provide the burst energy remains unclear. While many models have been proposed, those currently favored are all based upon the formation of and/or rapid accretion into stellar-mass black holes. Here we discuss a variety of such scenarios and estimate the probability of each. Population synthesis calculations are carried out using a Monte Carlo approach in which the many uncertain parameters intrinsic to such calculations are varied. We estimate the event rate for each class of model as well as the propagation distances for those having significant delay between formation and burst production, i.e., double neutron star (DNS) mergers and black hole-neutron star (BH/NS) mergers. One conclusion is a 1-2 order of magnitude decrease in the rate of DNS and BH/NS mergers compared to that previously calculated using invalid assumptions about common envelope evolution. Other major uncertainties in the event rates and propagation distances include the history of star formation in the universe, the masses of the galaxies in which merging compact objects are born, and the radii of the hydrogen-stripped cores of massive stars. For reasonable assumptions regarding each, we calculate a daily event rate in the universe for (1) merging neutron stars: ~100 day-1 (2) neutron star-black hole mergers: ~450 day-1 (3) collapsars: ~104 day-1 (4) helium star black hole mergers: ~1000 day-1 and (5) white dwarf-black hole mergers: ~20 day-1. The range of uncertainty in these numbers, however, is very large, typically 2-3 orders of magnitude. These rates must additionally be multiplied by any relevant beaming factor (fΩ<1) and sampling fraction (if the entire universal set of models is not being observed). Depending upon the mass of the host galaxy, one-half of

  20. Formation and growth rates of atmospheric nanoparticles: four years of observations at two West Siberian stations

    NASA Astrophysics Data System (ADS)

    Arshinov, Mikhail Yu.; Belan, Boris D.; Davydov, Denis K.; Kozlov, Artem V.; Arshinova, Victoria

    2015-04-01

    In spite of fact that the first report on the new particle formation (NPF) itself was done by John Aitken more than one century ago (Aitken, 1898), a phenomenon of NPF bursts taken place in the atmosphere was discovered not very long ago. Nevertheless, to date it is known that they may occur quite often in a variety of environments (Kulmala et al., 2004; Hirsikko et al., 2011). Siberia occupies a vast area covered by forests, but the comprehensive data on burst frequency, as well as on formation and growth rates of freshly nucleated particles in this key region are still lacking. Continuous measurements of aerosol size distribution carried out in recent years at two West Siberian stations (TOR-station - 56o28'41"N, 85o03'15"E; Fonovaya Observatory - 56o25'07"N, 84o04'27"E) allowed this gap in data to be filled up. Analysis of the size spectra classified in accordance with criteria proposed by Dal Maso et al. (2005) and Hammed et al. (2007) enabled a conclusion to be drawn that NPF events in Wets Siberia are more often observed during spring (from March to May) and early autumn (secondary frequency peak in September). On average, particle formation bursts took place on 23-28 % of all days. Such a seasonal pattern of the NPF occurrence is very similar to one observed at SMEAR II Station (Hyytiälä, Finland; Dal Maso et al. 2005, 2007). Formation rates (FR) of particles with diameters below 25 nm varied in a wide range from 0.1 to 10 cm-3 s-1. Mean values of FR for the entire period of observations were 1.7 cm-3s-1 (median = 1.13 cm-3 s-1) at TOR-station and 0.88 cm-3 s-1 (median = 0.69 cm-3 s-1) at Fonovaya Observatory. Enhanced values of FR are usually observed from spring to autumn. Mean growth rates of observed at TOR-station and Fonovaya Observatory were 6.5 nm h-1 (median = 5.0 nm h-1) and 8.3 nm h-1 (median = 6.4 nm h-1), respectively. This work was supported by the Branch of Geology, Geophysics and Mining Sciences of RAS (Program No. 5); State contracts of

  1. The Conditions Underpinning Extreme Star Formation in ULIRGs and LIRGs as Revealed by Herschel Far-Infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Vasquez, Gabriel A.; Ashby, Matthew; Smith, Howard Alan; McTier, Moiya; Melendez, Marcio

    2016-01-01

    We present a systematic survey of molecular and atomic line fluxes in all star-forming galaxies observed by the Herschel PACs instrument with detectable OH lines that also contain Herschel SPIRE FTS spectra, to determine how physical conditions vary as a function of star formation rate. Specifically, we measured selected CO, H2O, [CI], and [NII] integrated line fluxes in a sample of 145 star-forming galaxies covering a range of far-infrared luminosities ranging from 109 to above 1012 LSun . Thus, our sample includes typical, quiescent galaxies as well as Luminous Infrared Galaxies (LIRGs) and Ultra Luminous Infrared Galaxies (ULIRGs), known to be creating stars extremely rapidly. We find evidence suggesting that ULIRGs with far-infrared luminosities of LFIR> 1012 LSun require an additional heating mechanism other than UV heating from star formation, while LIRGs and less luminous star-forming galaxies may be heated primarily by their star formation. We also find that the [NII] 3P1 - 3P0 fine structure line flux and those of the CO J=5-4, CO J=7-6, and CO J=8-7 transitions are generally weaker for ULIRGs compared to LIRGs and less luminous star-forming galaxies, while we find the CO J=11-10, CO J=12-11, and CO J=13-12 transitions are generally stronger. In all these respects, ULIRGs are shown to differ significantly from other galaxies undergoing less extreme star formation. This work was supported in part by the NSF REU and DoD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution.

  2. Dinosaur Census Reveals Abundant Tyrannosaurus and Rare Ontogenetic Stages in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA

    PubMed Central

    Horner, John R.; Goodwin, Mark B.; Myhrvold, Nathan

    2011-01-01

    Background A dinosaur census recorded during the Hell Creek Project (1999–2009) incorporates multiple lines of evidence from geography, taphohistory, stratigraphy, phylogeny and ontogeny to investigate the relative abundance of large dinosaurs preserved in the Upper Cretaceous Hell Creek Formation of northeastern Montana, USA. Overall, the dinosaur skeletal assemblages in the Hell Creek Formation (excluding lag-influenced records) consist primarily of subadult or small adult size individuals. Small juveniles and large adults are both extremely rare, whereas subadult individuals are relatively common. We propose that mature individuals of at least some dinosaur taxa either lived in a separate geographic locale analogous to younger individuals inhabiting an upland environment where sedimentation rates were relatively less, or these taxa experienced high mortality before reaching terminal size where late stage and often extreme cranial morphology is expressed. Methodology/Principal Findings Tyrannosaurus skeletons are as abundant as Edmontosaurus, an herbivore, in the upper Hell Creek Formation and nearly twice as common in the lower third of the formation. Smaller, predatory dinosaurs (e.g., Troodon and dromaeosaurids) are primarily represented by teeth found in microvertebrate localities and their skeletons or identifiable lag specimens were conspicuously absent. This relative abundance suggests Tyrannosaurus was not a typical predator and likely benefited from much wider food choice opportunities than exclusively live prey and/or specific taxa. Tyrannosaurus adults may not have competed with Tyrannosaurus juveniles if the potential for selecting carrion increased with size during ontogeny. Conclusions/Significance Triceratops is the most common dinosaur and isolated skulls contribute to a significant portion of this census. Associated specimens of Triceratops consisting of both cranial and postcranial elements remain relatively rare. This rarity may be explained

  3. A CORRELATION BETWEEN STAR FORMATION RATE AND AVERAGE BLACK HOLE ACCRETION IN STAR-FORMING GALAXIES

    SciTech Connect

    Chen, Chien-Ting J.; Hickox, Ryan C.; Alberts, Stacey; Pope, Alexandra; Brodwin, Mark; Jones, Christine; Forman, William R.; Goulding, Andrew D.; Murray, Stephen S.; Alexander, David M.; Mullaney, James R.; Assef, Roberto J.; Gorjian, Varoujan; Brown, Michael J. I.; Dey, Arjun; Jannuzi, Buell T.; Le Floc'h, Emeric

    2013-08-10

    We present a measurement of the average supermassive black hole accretion rate (BHAR) as a function of the star formation rate (SFR) for galaxies in the redshift range 0.25 < z < 0.8. We study a sample of 1767 far-IR-selected star-forming galaxies in the 9 deg{sup 2} Booetes multi-wavelength survey field. The SFR is estimated using 250 {mu}m observations from the Herschel Space Observatory, for which the contribution from the active galactic nucleus (AGN) is minimal. In this sample, 121 AGNs are directly identified using X-ray or mid-IR selection criteria. We combined these detected AGNs and an X-ray stacking analysis for undetected sources to study the average BHAR for all of the star-forming galaxies in our sample. We find an almost linear relation between the average BHAR (in M{sub Sun} yr{sup -1}) and the SFR (in M{sub Sun} yr{sup -1}) for galaxies across a wide SFR range 0.85 < log SFR < 2.56: log BHAR = (- 3.72 {+-} 0.52) + (1.05 {+-} 0.33)log SFR. This global correlation between SFR and average BHAR is consistent with a simple picture in which SFR and AGN activity are tightly linked over galaxy evolution timescales.

  4. Effectiveness of intramuscularly administered cyanide antidotes and the rate of methemoglobin formation

    SciTech Connect

    Vick, J.A.; Von Bredow, J.D.

    1993-05-13

    Successful first aid therapy for cyanide intoxication is dependent upon the immediate administration of antidotes which directly or indirectly interact with the cyanide ion to remove it from circulation. Exceptionally rapid methemoglobin formers (hydroxylamine hydrochloride 'HA) and Dimethylaminophenol (DMAP) are usually able to prevent the lethal effect of cyanide following intramuscular injections in doses sufficient to induce 20% methemoglobin (HA = 20 mg/kg and DMAP= 2 mg/kg). Sodium nitrite, the methemoglobin inducer approved by the FDA and is available for military use, must be administered by intravenous infusion since it is not an effective cyanide antidote by the intramuscular route. In the normal un-intoxicated animal an intramuscular injection of 20 mg/kg sodium nitrite will form 20% methemoglobin at a rapid rate; however, in the presence of acute cyanide intoxication the associated severe bradycardia appears to limit the rate of absorption of sodium nitrite from the intramuscular site which prevents the rapid formation of sufficient methemoglobin to counteract cyanide intoxication.

  5. [Effect of Increasing Organic Loading Rate on the Formation and Stabilization Process of Aerobic Granular Sludge].

    PubMed

    Liu, Xiao-peng; Wang, Jan-fang; Qian, Fei-yue; Wang, Yan; Chen, Chong-jun; Shen, Yao-liang

    2015-09-01

    In order to evaluate the effect of organic loading rate ( OLR) on the formation of aerobic granular sludge (AGS), a lab-scale cylindrical SBR reactor (sodium acetate as carbon source) was constructed and inoculated with collected sewage sludge. The evolution of morphology, microbial activity and extracellular polymeric substances (EPS) characteristics of sludge samples in the reactor were recorded and analyzed. The results showed that AGS has the highest growth rate under the condition of 3. 20-4. 84 kg.(m3.d)-1 OLR, and a selective discharging strategy of the floccular sludge was suggested to maintain the predominance of AGS in reactor. The accumulated sludge concentration, SVI30, mean granule size, settling velocity and SOUR value of the AGS in steady-state operated SBR was 23. 9 g.L-1, 20 mL.g-1, 1. 4 mm, 102 m.h-1 and 50. 2 mg.(g.h)-1, respectively. The granulation process not only obviously changed the sludge appearance, but also significantly improved the microbial activity. Meanwhile, linear correlation was observed between the variation of protein/polysaccharide concentration and the granule size of AGS. Thus, variation of protein/ polysaccharide concentration of the EPS could be applied as an indicator for optimization of the cultivation method of AGS. PMID:26717698

  6. Growing black holes and galaxies: black hole accretion versus star formation rate

    NASA Astrophysics Data System (ADS)

    Volonteri, Marta; Capelo, Pedro R.; Netzer, Hagai; Bellovary, Jillian; Dotti, Massimo; Governato, Fabio

    2015-05-01

    We present a new suite of hydrodynamical simulations and use it to study, in detail, black hole and galaxy properties. The high time, spatial and mass resolution, and realistic orbits and mass ratios, down to 1:6 and 1:10, enable us to meaningfully compare star formation rate (SFR) and BH accretion rate (BHAR) time-scales, temporal behaviour, and relative magnitude. We find that (i) BHAR and galaxy-wide SFR are typically temporally uncorrelated, and have different variability time-scales, except during the merger proper, lasting ˜0.2-0.3 Gyr. BHAR and nuclear (<100 pc) SFR are better correlated, and their variability are similar. Averaging over time, the merger phase leads typically to an increase by a factor of a few in the BHAR/SFR ratio. (ii) BHAR and nuclear SFR are intrinsically proportional, but the correlation lessens if the long-term SFR is measured. (iii) Galaxies in the remnant phase are the ones most likely to be selected as systems dominated by an active galactic nucleus, because of the long time spent in this phase. (iv) The time-scale over which a given diagnostic probes the SFR has a profound impact on the recovered correlations with BHAR, and on the interpretation of observational data.

  7. Evaporation Rate Study and NDMA Formation from UDMH/NO2 Reaction Products

    NASA Technical Reports Server (NTRS)

    Buchanan, Vanessa D.; Dee, Louis A.; Baker, David L.

    2003-01-01

    Laboratory samples of uns-dimethylhydrazine (UDMH) fuel/oxidizer (nitrogen dioxide) non-combustion reaction products (UFORP) were prepared using a unique permeation tube technology. Also, a synthetic UFORP was prepared from UDMH, N-nitrosodimethylamine (NDMA), dimethylammonium nitrate, sodium nitrite and purified water. The evaporation rate of UFORP and synthetic UFORP was determined under space vacuum (approx 10(exp -3) Torr) at -40 ?C and 0 ?C. The material remaining was analyzed and showed that the UFORP weight and NDMA concentration decreased over time; however, NDMA had not completely evaporated. Over 85% of the weight was removed by subjecting the UFORP to 10(-3) Torr for 7 hours at -40 ?C and 4 hours at 0 ?C. A mixture of dimethylammonium nitrate and sodium nitrite formed NDMA at a rapid rate in a moist air environment. A sample of UFORP residue was analyzed for formation of NDMA under various conditions. It was found that NDMA was not formed unless nitrite was added.

  8. A rate theory study of helium bubble formation and retention in Cu-Nb nanocomposites

    NASA Astrophysics Data System (ADS)

    Dunn, A. Y.; McPhie, M. G.; Capolungo, L.; Martinez, E.; Cherkaoui, M.

    2013-04-01

    A spatially dependent rate theory model for helium migration, clustering, and trapping on interfaces between Cu and Nb layers is introduced to predict the evolution of the concentrations of He clusters of various sizes during implantation and early annealing. Migration and binding energies of point defects and small clusters in bulk Cu and Nb are found using conjugate gradient minimization and the nudged elastic band method. This model is implemented in a three-dimensional framework and used to predict the relationship between helium bubble formation and the nano-composite microstructure, including interfacial free volume, grain size, and layer thickness. Interstitial and vacancy-like migration of helium is considered. The effects of changing layer thickness and interfacial misfit dislocation density on the threshold for helium bubble nucleation are found to match experiments. Accelerated helium release due to interfaces and grain boundaries is shown to occur only when diffusion rates on interfaces and grain boundaries are greatly increased relative to the bulk material.

  9. The MOSDEF Survey: Mass, Metallicity, and Star-formation Rate at z~2.3

    NASA Astrophysics Data System (ADS)

    Sanders, Ryan Lee

    2015-08-01

    We present results on the z~2.3 mass-metallicity relation (MZR) using early observations from the MOSFIRE Deep Evolution Field (MOSDEF) survey. We use a sample of star-forming galaxies with spectroscopic coverage of Hβ, [OIII]λ5007, Hα, and [NII]λ6584 rest-frame optical emission lines, and estimate the gas-phase oxygen abundance based on the N2 and O3N2 strong-line indicators. We find a positive correlation between stellar mass and metallicity among individual z ˜ 2.3 galaxies using both the N2 and O3N2 indicators. We also measure the emission-line ratios and corresponding oxygen abundances for composite spectra in bins of stellar mass. Among composite spectra, we find a monotonic increase in metallicity with increasing stellar mass, offset ~0.15 - 0.3 dex below the local MZR. When the sample is divided at the median star-formation rate (SFR), we do not observe significant SFR dependence of the z~2.3 MZR among either individual galaxies or composite spectra. By directly comparing bins of local and high-redshift galaxies with similar stellar mass and SFR, we furthermore find that z~2.3 galaxies have metallicities ~0.1 dex lower at a given stellar mass and SFR than is observed locally. This offset suggests that high-redshift galaxies do not fall on the local “fundamental metallicity relation” among stellar mass, metallicity, and SFR, and may provide evidence of a phase of galaxy growth in which the gas reservoir is built up due to inflow rates that are higher than star-formation and outflow rates. However, robust conclusions regarding the gas-phase oxygen abundances of high-redshift galaxies await a systematic reappraisal of the application of locally calibrated metallicity indicators at high redshift. Using the MOSDEF dataset and photoionization models, we can also constrain the physical conditions (density, ionization state, hardness of the ionizing spectrum, metallicity) of high-redshift star-forming regions, providing one method of producing calibrations

  10. Rate of formation of carboxyhemoglobin in exercising humans exposed to carbon monoxide

    SciTech Connect

    Tikuisis, P.; Kane, D.M.; McLellan, T.M.; Buick, F.; Fairburn, S.M. )

    1992-04-01

    The purpose of this study was to test the CFK equation for its prediction of the rate of formation of carboxyhemoglobin (HbCO) in exercising humans by use of measured values of the respiratory variables and to characterize the rate of appearance of HbCO with frequent blood sampling. Ten nonsmoking male subjects were exposed to carbon monoxide (CO) on two separate occasions distinguished by the level of activity. Steady-state exercise was conducted on a cycle ergometer at either a low ([approximately]45 W) or moderate ([approximately]90W) power output. Each experiment began with an exposure of 3,000 ppm CO for 3 min during a rest period followed by three intermittent exposures ranging from 3,000 ppm CO for 1 min at low exercise to 667 ppm CO for 3 min at moderate exercise. Increases in HbCO were normalized against predicted values to account for individual differences in the variables that govern CO uptake. No difference in the normalized uptake of CO was found between the low-and moderate-exercise trials. However, the CFK equation underpredicted the increase in HbCO for the exposures at rest and the first exposure at exercise, whereas it overpredicted for the latter two exposures at exercise. The net increase in HbCO after all exposures ([approximately]10% HbCO) deviated by <1% HbCO between the measured and predicted values. The rate of appearance of HbCO fits a sigmoidal shape with considerable overshoot at the end of exposure. This can be explained by delays in the delivery of CO to the blood sampling point (dorsal hand vein) and by a relatively small blood circulation time compared with other regions of the body. A simple circulation model is used to demonstrate the overshoot phenomenon. 26 refs., 6 figs., 1 tab.

  11. Atomic force microscopy imaging reveals the formation of ASIC/ENaC cross-clade ion channels

    SciTech Connect

    Jeggle, Pia; Smith, Ewan St. J.; Stewart, Andrew P.; Haerteis, Silke; Korbmacher, Christoph; Edwardson, J. Michael

    2015-08-14

    ASIC and ENaC are co-expressed in various cell types, and there is evidence for a close association between them. Here, we used atomic force microscopy (AFM) to determine whether ASIC1a and ENaC subunits are able to form cross-clade hybrid ion channels. ASIC1a and ENaC could be co-isolated from detergent extracts of tsA 201 cells co-expressing the two subunits. Isolated proteins were incubated with antibodies against ENaC and Fab fragments against ASIC1a. AFM imaging revealed proteins that were decorated by both an antibody and a Fab fragment with an angle of ∼120° between them, indicating the formation of ASIC1a/ENaC heterotrimers. - Highlights: • There is evidence for a close association between ASIC and ENaC. • We used AFM to test whether ASIC1a and ENaC subunits form cross-clade ion channels. • Isolated proteins were incubated with subunit-specific antibodies and Fab fragments. • Some proteins were doubly decorated at ∼120° by an antibody and a Fab fragment. • Our results indicate the formation of ASIC1a/ENaC heterotrimers.

  12. 13C Tracking after 13CO2 Supply Revealed Diurnal Patterns of Wood Formation in Aspen1

    PubMed Central

    Mahboubi, Amir; Linden, Pernilla; Moritz, Thomas

    2015-01-01

    Wood of trees is formed from carbon assimilated in the photosynthetic tissues. Determining the temporal dynamics of carbon assimilation, subsequent transport into developing wood, and incorporation to cell walls would further our understanding of wood formation in particular and tree growth in general. To investigate these questions, we designed a 13CO2 labeling system to study carbon transport and incorporation to developing wood of hybrid aspen (Populus tremula × tremuloides). Tracking of 13C incorporation to wood over a time course using nuclear magnetic resonance spectroscopy revealed diurnal patterns in wood cell wall biosynthesis. The dark period had a differential effect on 13C incorporation to lignin and cell wall carbohydrates. No 13C was incorporated into aromatic amino acids of cell wall proteins in the dark, suggesting that cell wall protein biosynthesis ceased during the night. The results show previously unrecognized temporal patterns in wood cell wall biosynthesis, suggest diurnal cycle as a possible cue in the regulation of carbon incorporation to wood, and establish a unique 13C labeling method for the analysis of wood formation and secondary growth in trees. PMID:25931520

  13. The Metabolic Regulation of Sporulation and Parasporal Crystal Formation in Bacillus thuringiensis Revealed by Transcriptomics and Proteomics*

    PubMed Central

    Wang, Jieping; Mei, Han; Zheng, Cao; Qian, Hongliang; Cui, Cui; Fu, Yang; Su, Jianmei; Liu, Ziduo; Yu, Ziniu; He, Jin

    2013-01-01

    Bacillus thuringiensis is a well-known entomopathogenic bacterium used worldwide as an environmentally compatible biopesticide. During sporulation, B. thuringiensis accumulates a large number of parasporal crystals consisting of insecticidal crystal proteins (ICPs) that can account for nearly 20–30% of the cell's dry weight. However, the metabolic regulation mechanisms of ICP synthesis remain to be elucidated. In this study, the combined efforts in transcriptomics and proteomics mainly uncovered the following 6 metabolic regulation mechanisms: (1) proteases and the amino acid metabolism (particularly, the branched-chain amino acids) became more active during sporulation; (2) stored poly-β-hydroxybutyrate and acetoin, together with some low-quality substances provided considerable carbon and energy sources for sporulation and parasporal crystal formation; (3) the pentose phosphate shunt demonstrated an interesting regulation mechanism involving gluconate when CT-43 cells were grown in GYS medium; (4) the tricarboxylic acid cycle was significantly modified during sporulation; (5) an obvious increase in the quantitative levels of enzymes and cytochromes involved in energy production via the electron transport system was observed; (6) most F0F1-ATPase subunits were remarkably up-regulated during sporulation. This study, for the first time, systematically reveals the metabolic regulation mechanisms involved in the supply of amino acids, carbon substances, and energy for B. thuringiensis spore and parasporal crystal formation at both the transcriptional and translational levels. PMID:23408684

  14. Revealing energy level structure of individual quantum dots by tunneling rate measured by single-electron sensitive electrostatic force spectroscopy.

    PubMed

    Roy-Gobeil, Antoine; Miyahara, Yoichi; Grutter, Peter

    2015-04-01

    We present theoretical and experimental studies of the effect of the density of states of a quantum dot (QD) on the rate of single-electron tunneling that can be directly measured by electrostatic force microscopy (e-EFM) experiments. In e-EFM, the motion of a biased atomic force microscope cantilever tip modulates the charge state of a QD in the Coulomb blockade regime. The charge dynamics of the dot, which is detected through its back-action on the capacitavely coupled cantilever, depends on the tunneling rate of the QD to a back-electrode. The density of states of the QD can therefore be measured through its effect on the energy dependence of tunneling rate. We present experimental data on individual 5 nm colloidal gold nanoparticles that exhibit a near continuous density of state at 77 K. In contrast, our analysis of already published data on self-assembled InAs QDs at 4 K clearly reveals discrete degenerate energy levels. PMID:25761141

  15. Genetic map of the human pseudoautosomal region reveals a high rate of recombination in female meiosis at the Xp telomere

    SciTech Connect

    Henke, A.; Fischer, C.; Rappold, G.A. )

    1993-12-01

    This paper describes the genetic map of the pseudoautosomal region bounded by the telomere of the short arms of the X and Y chromosomes. In males, meiotic exchange on Xp/Yp is confined to this region, leading to highly elevated recombination rates. The map was constructed using 11 pseudoautosomal probes (six of which are new) and typing individuals from 38 CEPH families. All markers have been physically mapped, thus providing the opportunity to compare genetic distance to physical distance through all intervals of the map. This comparison reveals an unexpected high rate of recombination in female meiosis between loci DXYS20 and DXYS78, within 20-80 kb from the telomere. Within this telemore-adjacent region no differences in male and female recombination rates are seen. Furthermore, data from this genetic map support the hypothesis of a linear gradient of recombination across most of the region in male meiosis and provide densely spaced anchor points for linkage studies especially in the telomeric portion of the pseudoautosomal region. 34 refs., 4 figs., 4 tabs.

  16. A probabilistic analysis reveals fundamental limitations with the environmental impact quotient and similar systems for rating pesticide risks

    PubMed Central

    Schleier, Jerome J.

    2014-01-01

    Comparing risks among pesticides has substantial utility for decision makers. However, if rating schemes to compare risks are to be used, they must be conceptually and mathematically sound. We address limitations with pesticide risk rating schemes by examining in particular the Environmental Impact Quotient (EIQ) using, for the first time, a probabilistic analytic technique. To demonstrate the consequences of mapping discrete risk ratings to probabilities, adjusted EIQs were calculated for a group of 20 insecticides in four chemical classes. Using Monte Carlo simulation, adjusted EIQs were determined under different hypothetical scenarios by incorporating probability ranges. The analysis revealed that pesticides that have different EIQs, and therefore different putative environmental effects, actually may be no different when incorporating uncertainty. The EIQ equation cannot take into account uncertainty the way that it is structured and provide reliable quotients of pesticide impact. The EIQ also is inconsistent with the accepted notion of risk as a joint probability of toxicity and exposure. Therefore, our results suggest that the EIQ and other similar schemes be discontinued in favor of conceptually sound schemes to estimate risk that rely on proper integration of toxicity and exposure information. PMID:24795854

  17. Offset of latest pleistocene shoreface reveals slip rate on the Hosgri strike-slip fault, offshore central California

    USGS Publications Warehouse

    Johnson, Samuel Y.; Hartwell, Stephen R.; Dartnell, Peter

    2014-01-01

    The Hosgri fault is the southern part of the regional Hosgri–San Gregorio dextral strike‐slip fault system, which extends primarily in the offshore for about 400 km in central California. Between Morro Bay and San Simeon, high‐resolution multibeam bathymetry reveals that the eastern strand of the Hosgri fault is crossed by an ∼265  m wide slope interpreted as the shoreface of a latest Pleistocene sand spit. This sand spit crossed an embayment and connected a western fault‐bounded bedrock peninsula and an eastern bedrock highland, a paleogeography resembling modern coastal geomorphology along the San Andreas fault. Detailed analysis of the relict shoreface with slope profiles and slope maps indicates a lateral slip rate of 2.6±0.9  mm/yr, considered a minimum rate for the Hosgri given the presence of an active western strand. This slip rate indicates that the Hosgri system takes up the largest share of the strike‐slip fault budget and is the most active strike‐slip fault west of the San Andreas fault in central California. This result further demonstrates the value and potential of high‐resolution bathymetry in characterization of active offshore faults.

  18. A chamber study of the influence of boreal BVOC emissions and sulphuric acid on nanoparticle formation rates at ambient concentrations

    NASA Astrophysics Data System (ADS)

    Dal Maso, M.; Liao, L.; Wildt, J.; Kiendler-Scharr, A.; Kleist, E.; Tillmann, R.; Sipilä, M.; Hakala, J.; Lehtipalo, K.; Ehn, M.; Kerminen, V.-M.; Kulmala, M.; Worsnop, D.; Mentel, T.

    2014-12-01

    Aerosol formation from biogenic and anthropogenic precursor trace gases in continental background areas affects climate via altering the amount of available cloud condensation nuclei. Significant uncertainty still exists regarding the agents controlling the formation of aerosol nanoparticles. We have performed experiments in the Jülich Plant-Atmosphere Simulation Chamber with instrumentation for the detection of sulphuric acid and nanoparticles, and present the first simultaneous chamber observations of nanoparticles, sulphuric acid, and realistic levels and mixtures of biogenic volatile compounds (BVOC). We present direct laboratory observations of nanoparticle formation from sulphuric acid and realistic BVOC precursor vapor mixtures performed at atmospherically relevant concentration levels. We directly measured particle formation rates separately from particle growth rates. From this, we established that in our experiments, the formation rate was proportional to the product of sulphuric acid and biogenic VOC emission strength. The formation rates were consistent with a mechanism in which nucleating BVOC oxidation products are rapidly formed and activate with sulphuric acid. The growth rate of nanoparticles immediately after birth was best correlated with estimated products resulting from BVOC ozonolysis.

  19. A chamber study of the influence of boreal BVOC emissions and sulfuric acid on nanoparticle formation rates at ambient concentrations

    NASA Astrophysics Data System (ADS)

    Dal Maso, M.; Liao, L.; Wildt, J.; Kiendler-Scharr, A.; Kleist, E.; Tillmann, R.; Sipilä, M.; Hakala, J.; Lehtipalo, K.; Ehn, M.; Kerminen, V.-M.; Kulmala, M.; Worsnop, D.; Mentel, T.

    2016-02-01

    Aerosol formation from biogenic and anthropogenic precursor trace gases in continental background areas affects climate via altering the amount of available cloud condensation nuclei. Significant uncertainty still exists regarding the agents controlling the formation of aerosol nanoparticles. We have performed experiments in the Jülich plant-atmosphere simulation chamber with instrumentation for the detection of sulfuric acid and nanoparticles, and present the first simultaneous chamber observations of nanoparticles, sulfuric acid, and realistic levels and mixtures of biogenic volatile compounds (BVOCs). We present direct laboratory observations of nanoparticle formation from sulfuric acid and realistic BVOC precursor vapour mixtures performed at atmospherically relevant concentration levels. We directly measured particle formation rates separately from particle growth rates. From this, we established that in our experiments, the formation rate was proportional to the product of sulfuric acid and biogenic VOC emission strength. The formation rates were consistent with a mechanism in which nucleating BVOC oxidation products are rapidly formed and activate with sulfuric acid. The growth rate of nanoparticles immediately after birth was best correlated with estimated products resulting from BVOC ozonolysis.

  20. Predicting Galaxy Star Formation Rates via the Co-evolution of Galaxies and Halos

    SciTech Connect

    Watson, Douglas F.; Hearin, Andrew P.; Berlind, Andreas A.; Becker, Matthew R.; Behroozi, Peter S.; Skibba, Ramin A.; Reyes, Reinabelle; Zentner, Andrew R.

    2014-03-06

    In this paper, we test the age matching hypothesis that the star formation rate (SFR) of a galaxy is determined by its dark matter halo formation history, and as such, that more quiescent galaxies reside in older halos. This simple model has been remarkably successful at predicting color-based galaxy statistics at low redshift as measured in the Sloan Digital Sky Survey (SDSS). To further test this method with observations, we present new SDSS measurements of the galaxy two-point correlation function and galaxy-galaxy lensing as a function of stellar mass and SFR, separated into quenched and star forming galaxy samples. We find that our age matching model is in excellent agreement with these new measurements. We also employ a galaxy group finder and show that our model is able to predict: (1) the relative SFRs of central and satellite galaxies, (2) the SFR-dependence of the radial distribution of satellite galaxy populations within galaxy groups, rich groups, and clusters and their surrounding larger scale environments, and (3) the interesting feature that the satellite quenched fraction as a function of projected radial distance from the central galaxy exhibits an approx r-.15 slope, independent of environment. The accurate prediction for the spatial distribution of satellites is intriguing given the fact that we do not explicitly model satellite-specific processes after infall, and that in our model the virial radius does not mark a special transition region in the evolution of a satellite, contrary to most galaxy evolution models. The success of the model suggests that present-day galaxy SFR is strongly correlated with halo mass assembly history.

  1. The ultraviolet and infrared star formation rates of compact group galaxies: an expanded sample

    NASA Astrophysics Data System (ADS)

    Lenkić, Laura; Tzanavaris, Panayiotis; Gallagher, Sarah C.; Desjardins, Tyler D.; Walker, Lisa May; Johnson, Kelsey E.; Fedotov, Konstantin; Charlton, Jane; Hornschemeier, Ann E.; Durrell, Pat R.; Gronwall, Caryl

    2016-07-01

    Compact groups of galaxies provide insight into the role of low-mass, dense environments in galaxy evolution because the low velocity dispersions and close proximity of galaxy members result in frequent interactions that take place over extended time-scales. We expand the census of star formation in compact group galaxies by Tzanavaris et al. (2010) and collaborators with Swift UVOT, Spitzer IRAC and MIPS 24 μm photometry of a sample of 183 galaxies in 46 compact groups. After correcting luminosities for the contribution from old stellar populations, we estimate the dust-unobscured star formation rate (SFRUV) using the UVOT uvw2 photometry. Similarly, we use the MIPS 24 μm photometry to estimate the component of the SFR that is obscured by dust (SFRIR). We find that galaxies which are MIR-active (MIR-`red'), also have bluer UV colours, higher specific SFRs, and tend to lie in H I-rich groups, while galaxies that are MIR-inactive (MIR-`blue') have redder UV colours, lower specific SFRs, and tend to lie in H I-poor groups. We find the SFRs to be continuously distributed with a peak at about 1 M⊙ yr-1, indicating this might be the most common value in compact groups. In contrast, the specific SFR distribution is bimodal, and there is a clear distinction between star-forming and quiescent galaxies. Overall, our results suggest that the specific SFR is the best tracer of gas depletion and galaxy evolution in compact groups.

  2. ESTIMATING THE STAR FORMATION RATE AT 1 kpc SCALES IN NEARBY GALAXIES

    SciTech Connect

    Leroy, Adam K.; Munoz-Mateos, Juan-Carlos; Bigiel, Frank; De Blok, W. J. G.; Boissier, Samuel; Bolatto, Alberto; Brinks, Elias; Madore, Barry; Murphy, Eric; Sandstrom, Karin; Schruba, Andreas; Walter, Fabian

    2012-07-15

    Using combinations of H{alpha}, ultraviolet (UV), and infrared (IR) emission, we estimate the star formation rate (SFR) surface density, {Sigma}{sub SFR}, at 1 kpc resolution for 30 disk galaxies that are targets of the IRAM HERACLES CO survey. We present a new physically motivated IR spectral-energy-distribution-based approach to account for possible contributions to 24 {mu}m emission not associated with recent star formation. Considering a variety of 'reference' SFRs from the literature, we revisit the calibration of the 24 {mu}m term in hybrid (UV+IR or H{alpha}+IR) tracers. We show that the overall calibration of this term remains uncertain at the factor of two level because of the lack of wide-field, robust reference SFR estimates. Within this uncertainty, published calibrations represent a reasonable starting point for 1 kpc-wide areas of star-forming disk galaxies, but we re-derive and refine the calibration of the IR term in these tracers to match our resolution and approach to 24 {mu}m emission. We compare a large suite of {Sigma}{sub SFR} estimates and find that above {Sigma}{sub SFR} {approx} 10{sup -3} M{sub Sun} yr{sup -1} kpc{sup -2} the systematic differences among tracers are less than a factor of two across two orders of magnitude dynamic range. We caution that methodology and data both become serious issues below this level. We note from simple model considerations that when focusing on a part of a galaxy dominated by a single stellar population, the intrinsic uncertainty in H{alpha}- and FUV-based SFRs is {approx}0.3 and {approx}0.5 dex.

  3. Dipyrenylphosphatidylcholines as membrane fluidity probes. Pressure and temperature dependence of the intramolecular excimer formation rate.

    PubMed Central

    Sassaroli, M; Vauhkonen, M; Somerharju, P; Scarlata, S

    1993-01-01

    We have measured the pressure dependence of the intramolecular excimer formation rate, K(p), for di-(1'-pyrenedecanoyl)-phosphatidylcholine (dipy10PC) probes in single-component lipid multilamellar vesicles (MLV) as a function of temperature. Apparent volumes of activation (V(a)) for intramolecular excimer formation are obtained from the slopes of plots of log K(p) versus P. For liquid-crystalline saturated lipid MLV (DMPC and DPPC), these plots are linear and yield a unique V(a) at each temperature, whereas for unsaturated lipids (POPC and DOPC) they are curvilinear and V(a) appears to decrease with pressure. The isothermal pressure induced phase transition is marked by an abrupt drop in the values of K(p). The pressure to temperature equivalence values, dPm/dT, estimated from the midpoint of the transitions, are 47.0, 43.5, and 52.5 bar degree C-1 for DMPC, DPPC, and POPC, respectively. In liquid-crystalline DMPC, V(a) decreases linearly as a function of temperature, with a coefficient -dVa/dT = 0.65 +/- 0.11 ml degree C-1 mol-1. Using a modified free volume model of diffusion, we show that this value corresponds to the thermal expansivity of DMPC. Both the apparent energy and entropy of activation, Ea and delta Sa, increase with pressure in DMPC, whereas both decrease in POPC and DOPC. This difference is attributed to the sensitivity of the dynamics and/or packing of the dipy10PC probes to the location of the cis-double bonds in the chains of the unsaturated host phospholipids. Finally, the atmospheric pressure values of Ea and delta Sa for the four host MLV examined are shown to be linearly related. The relevance of this finding with respect to the structure of the excimers formed by the dipy10PC probes is briefly discussed. PMID:8431538

  4. Star formation rates and chemical abundances of emission-line galaxies in intermediate-redshift clusters

    NASA Astrophysics Data System (ADS)

    Mouhcine, M.; Bamford, S. P.; Aragón-Salamanca, A.; Nakamura, O.; Milvang-Jensen, B.

    2006-06-01

    We examine the evolutionary status of luminous, star-forming galaxies in intermediate-redshift clusters by considering their star formation rates (SFRs) and the chemical and ionization properties of their interstellar emitting gas. Our sample consists of 17 massive, star-forming, mostly disc galaxies with MB<~-20, in clusters with redshifts in the range 0.31 <~z<~ 0.59, with a median of = 0.42. We compare these galaxies with the identically selected and analysed intermediate-redshift field sample of Mouhcine et al., and with local galaxies from the Nearby Field Galaxy Survey of Jansen et al. From our optical spectra, we measure the equivalent widths of [OII]λ3727, Hβ and [OIII]λ5007 emission lines to determine diagnostic line ratios, oxygen abundances and extinction-corrected SFRs. The star-forming galaxies in intermediate-redshift clusters display emission-line equivalent widths which are, on average, significantly smaller than measured for field galaxies at comparable redshifts. However, a contrasting fraction of our cluster galaxies have equivalent widths similar to the highest observed in the field. This tentatively suggests a bimodality in the SFRs per unit luminosity for galaxies in distant clusters. We find no evidence for further bimodalities, or differences between our cluster and field samples, when examining additional diagnostics and the oxygen abundances of our galaxies. This maybe because no such differences exist, perhaps because the cluster galaxies which still display signs of star formation have recently arrived from the field. In order to examine this topic with more certainty, and to further investigate the way in which any disparity varies as a function of cluster properties, larger spectroscopic samples are needed.

  5. SUSTAINING STAR FORMATION RATES IN SPIRAL GALAXIES: SUPERNOVA-DRIVEN TURBULENT ACCRETION DISK MODELS APPLIED TO THINGS GALAXIES

    SciTech Connect

    Vollmer, Bernd; Leroy, Adam K.

    2011-01-15

    Gas disks of spiral galaxies can be described as clumpy accretion disks without a coupling of viscosity to the actual thermal state of the gas. The model description of a turbulent disk consisting of emerging and spreading clumps contains free parameters, which can be constrained by observations of molecular gas, atomic gas, and the star formation rate for individual galaxies. Radial profiles of 18 nearby spiral galaxies from THINGS, HERACLES, SINGS, and GALEX data are used to compare the observed star formation efficiency, molecular fraction, and velocity dispersion to the model. The observed radially decreasing velocity dispersion can be reproduced by the model. In the framework of this model, the decrease in the inner disk is due to the stellar mass distribution which dominates the gravitational potential. Introducing a radial break in the star formation efficiency into the model improves the fits significantly. This change in the star formation regime is realized by replacing the free-fall time in the prescription of the star formation rate with the molecule formation timescale. Depending on the star formation prescription, the break radius is located near the transition region between the molecular-gas-dominated and atomic-gas-dominated parts of the galactic disk or closer to the optical radius. It is found that only less massive galaxies (log M(M{sub sun}) {approx}< 10) can balance gas loss via star formation by radial gas accretion within the disk. These galaxies can thus access their gas reservoirs with large angular momentum. On the other hand, the star formation of massive galaxies is determined by the external gas mass accretion rate from a putative spherical halo of ionized gas or from satellite accretion. In the absence of this external accretion, star formation slowly exhausts the gas within the optical disk within the star formation timescale.

  6. Rapid Circumstellar Disk Evolution and an Accelerating Star Formation Rate in the Infrared Dark Cloud M17 SWex

    NASA Astrophysics Data System (ADS)

    Povich, Matthew S.; Townsley, Leisa K.; Robitaille, Thomas P.; Broos, Patrick S.; Orbin, Wesley T.; King, Robert R.; Naylor, Tim; Whitney, Barbara A.

    2016-07-01

    We present a catalog of 840 X-ray sources and first results from a 100 ks Chandra X-ray Observatory imaging study of the filamentary infrared (IR) dark cloud G014.225–00.506, which forms the central regions of a larger cloud complex known as the M17 southwest extension (M17 SWex). In addition to the rich population of protostars and young stellar objects with dusty circumstellar disks revealed by archival data from the Spitzer Space Telescope, we discover a population of X-ray-emitting, intermediate-mass pre-main-sequence stars that lack IR excess emission from circumstellar disks. We model the IR spectral energy distributions of this source population to measure its mass function and place new constraints on the destruction timescales for the inner dust disk for 2–8 M ⊙ stars. We also place a lower limit on the star formation rate (SFR) and find that it is quite high (\\dot{M}≥slant 0.007 M ⊙ yr‑1), equivalent to several Orion Nebula Clusters in G14.225–0.506 alone, and likely accelerating. The cloud complex has not produced a population of massive, O-type stars commensurate with its SFR. This absence of very massive (≳20 M ⊙) stars suggests that either (1) M17 SWex is an example of a distributed mode of star formation that will produce a large OB association dominated by intermediate-mass stars but relatively few massive clusters, or (2) the massive cores are still in the process of accreting sufficient mass to form massive clusters hosting O stars.

  7. Local SDSS galaxies in the Herschel Stripe 82 survey: a critical assessment of optically derived star formation rates

    NASA Astrophysics Data System (ADS)

    Rosario, D. J.; Mendel, J. T.; Ellison, S. L.; Lutz, D.; Trump, J. R.

    2016-04-01

    We study a set of 3319 galaxies in the redshift interval 0.04 < z < 0.15 with far-infrared (FIR) coverage from the Herschel Stripe 82 survey (HerS), and emission-line measurements, redshifts, stellar masses and star formation rates (SFRs) from the Sloan Digital Sky Survey (SDSS) (DR7) MPA/JHU data base. About 40 per cent of the sample are detected in the Herschel/SPIRE 250 μm band. Total infrared (TIR) luminosities derived from HerS and Wide-field Infrared Survey Explorer (WISE) photometry allow us to compare infrared and optical estimates of SFR with unprecedented statistics for diverse classes of galaxies. We find excellent agreement between TIR-derived and emission line-based SFRs for H II galaxies. Other classes, such as active galaxies and evolved galaxies, exhibit systematic discrepancies between optical and TIR SFRs. We demonstrate that these offsets are attributable primarily to survey biases and the large intrinsic uncertainties of the Dn4000- and colour-based optical calibrations used to estimate the SDSS SFRs of these galaxies. Using a classification scheme which expands upon popular emission-line methods, we demonstrate that emission-line galaxies with uncertain classifications include a population of massive, dusty, metal-rich star-forming systems that are frequently neglected in existing studies. We also study the capabilities of infrared selection of star-forming galaxies. FIR selection reveals a substantial population of galaxies dominated by cold dust which are missed by the long-wavelength WISE bands. Our results demonstrate that Herschel large-area surveys offer the means to construct large, relatively complete samples of local star-forming galaxies with accurate estimates of SFR that can be used to study the interplay between nuclear activity and star formation.

  8. The Impact of Evolving Infrared Spectral Energy Distributions of Galaxies on Star Formation Rate Estimates

    NASA Astrophysics Data System (ADS)

    Nordon, R.; Lutz, D.; Genzel, R.; Berta, S.; Wuyts, S.; Magnelli, B.; Altieri, B.; Andreani, P.; Aussel, H.; Bongiovanni, A.; Cepa, J.; Cimatti, A.; Daddi, E.; Fadda, D.; Förster Schreiber, N. M.; Lagache, G.; Maiolino, R.; Pérez García, A. M.; Poglitsch, A.; Popesso, P.; Pozzi, F.; Rodighiero, G.; Rosario, D.; Saintonge, A.; Sanchez-Portal, M.; Santini, P.; Sturm, E.; Tacconi, L. J.; Valtchanov, I.; Yan, L.

    2012-02-01

    We combine Herschel-Photodetector Array Camera and Spectrometer (PACS) data from the PACS Evolutionary Probe (PEP) program with Spitzer 24 μm and 16 μm photometry and ultra deep Infrared Spectrograph (IRS) mid-infrared spectra to measure the mid- to far-infrared spectral energy distribution (SED) of 0.7 < z < 2.5 normal star-forming galaxies (SFGs) around the main sequence (the redshift-dependent relation of star formation rate (SFR) and stellar mass). Our very deep data confirm from individual far-infrared detections that z ~ 2 SFRs are overestimated if based on 24 μm fluxes and SED templates that are calibrated via local trends with luminosity. Galaxies with similar ratios of rest-frame νL ν(8) to 8-1000 μm infrared luminosity (LIR) tend to lie along lines of constant offset from the main sequence. We explore the relation between SED shape and offset in specific star formation rate (SSFR) from the redshift-dependent main sequence. Main-sequence galaxies tend to have a similar νL ν(8)/LIR regardless of LIR and redshift, up to z ~ 2.5, and νL ν(8)/LIR decreases with increasing offset above the main sequence in a consistent way at the studied redshifts. We provide a redshift-independent calibration of SED templates in the range of 8-60 μm as a function of Δlog(SSFR) offset from the main sequence. Redshift dependency enters only through the evolution of the main sequence with time. Ultra deep IRS spectra match these SED trends well and verify that they are mostly due to a change in ratio of polycyclic aromatic hydrocarbon (PAH) to LIR rather than continua of hidden active galactic nuclei (AGNs). Alternatively, we discuss the dependence of νL ν(8)/LIR on LIR. The same νL ν(8)/LIR is reached at increasingly higher LIR at higher redshift, with shifts relative to local by 0.5 and 0.8 dex in log(LIR) at redshifts z ~ 1 and z ~ 2. Corresponding SED template calibrations are provided for use if no stellar masses are on hand. For most of those z ~ 2 SFGs that

  9. Constraints on timing and rates of strath terrace formation on actively uplifting anticlines in the foreland of the Chinese Tien Shan.

    NASA Astrophysics Data System (ADS)

    Bufe, A.; Burbank, D. W.; Chen, J.; Liu, L.; Li, T.; Thompson, J. A.

    2014-12-01

    The formation of strath surfaces (fluvially created, sub-horizontal erosion surfaces) requires that the rate of lateral erosion outpaces the rate of incision of a river. The change from incision to strath cutting has commonly been linked to a decrease of incision rates due to shielding of the river bed by a thick sediment cover1. Straths are abandoned when the bed cover is reduced and incision resumes. A more recent study suggests that strath terrace formation might be linked to a change between a braided and a single-thread river2. Finally, several models have explored strath formation due to inherent dynamics of meandering systems3,4. In the foreland of the Tian Shan in northwest China, weakly consolidated Pliocene sand and siltstones are being actively uplifted at rates of 1 - 3 mm/y by a series of detachment anticlines. A number of elevated, several-kilometer-wide planation surfaces bear witness to a history of multiple strath cutting events by braided streams. In contrast, modern rivers incise into the uplifting folds creating 10 - 200 m deep canyons while the up- and downstream alluvial fans remain unincised. We use GIS analysis, field mapping, and OSL dating to describe incision and beveling of the folds. Our chronologic data reveal at least 2 - 3 beveling events over the last 40 ky on the Mutule fold. We find that lateral erosion of the bedrock during beveling events occurs at rates that are more than an order of magnitude higher than average incision rates. During times of incision (which can be tens of thousands of years long), lateral erosion rates need to be considerably lower in order to explain the formation of narrow canyons. Thus, our observations of scale, rate, and intermittency of strath cutting, seem difficult to reconcile with models that explain strath formation by variations of the incision rate1 or intrinsic meandering dynamics under steady forcing3,4. The critical requirement to explain our observations appears to be repeated changes in the

  10. The most distant galaxies: star formation rates, stellar populations and contribution to reionization

    NASA Astrophysics Data System (ADS)

    Bunker, Andrew; Stanway, Elizabeth R.; Wilkins, Stephen M.

    2015-08-01

    Over the last decade we have identified the first galaxies at redshift 6 and beyond, within the first billion years when the Gunn-Peterson absorption produces significant Lyman breaks in the spectra. Since the original Hubble Ultra Deep Field (HUDF) was imaged with HST/ACS, the advent of sensitive near-infrared imaging on HST with WFC3 has enabled us to push the use of the Lyman break technique to redshifts between 7 and 12, within the epoch of reionization. Rest-frame UV luminosity functions derived from various deep HST fields such as the HUDF and Frontier Fields, wider field imaging such as CANDELS, and ground-based imaging such as UltraVISTA, can be used to constrain the contribution of ionizing photons from star-forming galaxies. I will review what we have learned about the role of galaxies in the reionization of the IGM, and discuss the implications of the observed blue spectral slopes at these epochs and the redshift evolution of the fraction of strong Lyman-alpha emitters. Coupled with observations from Spitzer/IRAC, we can estimate the stellar masses as well as star formation rates for this population of proto-galaxies. I will look ahead to the prospects with JWST, in particular our NIRSpec GTO programme to obtain spectra of star-forming galaxies within the epoch of reionization.

  11. GAMA/H-ATLAS: common star formation rate indicators and their dependence on galaxy physical parameters

    NASA Astrophysics Data System (ADS)

    Wang, L.; Norberg, P.; Gunawardhana, M. L. P.; Heinis, S.; Baldry, I. K.; Bland-Hawthorn, J.; Bourne, N.; Brough, S.; Brown, M. J. I.; Cluver, M. E.; Cooray, A.; da Cunha, E.; Driver, S. P.; Dunne, L.; Dye, S.; Eales, S.; Grootes, M. W.; Holwerda, B. W.; Hopkins, A. M.; Ibar, E.; Ivison, R.; Lacey, C.; Lara-Lopez, M. A.; Loveday, J.; Maddox, S. J.; Michałowski, M. J.; Oteo, I.; Owers, M. S.; Popescu, C. C.; Smith, D. J. B.; Taylor, E. N.; Tuffs, R. J.; van der Werf, P.

    2016-09-01

    We compare common star formation rate (SFR) indicators in the local Universe in the Galaxy and Mass Assembly (GAMA) equatorial fields (˜160 deg2), using ultraviolet (UV) photometry from GALEX, far-infrared and sub-millimetre (sub-mm) photometry from Herschel Astrophysical Terahertz Large Area Survey, and Hα spectroscopy from the GAMA survey. With a high-quality sample of 745 galaxies (median redshift = 0.08), we consider three SFR tracers: UV luminosity corrected for dust attenuation using the UV spectral slope β (SFRUV, corr), Hα line luminosity corrected for dust using the Balmer decrement (BD) (SFRH α, corr), and the combination of UV and infrared (IR) emission (SFRUV + IR). We demonstrate that SFRUV, corr can be reconciled with the other two tracers after applying attenuation corrections by calibrating Infrared excess (IRX; i.e. the IR to UV luminosity ratio) and attenuation in the Hα (derived from BD) against β. However, β, on its own, is very unlikely to be a reliable attenuation indicator. We find that attenuation correction factors depend on parameters such as stellar mass (M*), z and dust temperature (Tdust), but not on Hα equivalent width or Sérsic index. Due to the large scatter in the IRX versus β correlation, when compared to SFRUV + IR, the β-corrected SFRUV, corr exhibits systematic deviations as a function of IRX, BD and Tdust.

  12. PANCHROMATIC ESTIMATION OF STAR FORMATION RATES IN BzK GALAXIES AT 1 < z < 3

    SciTech Connect

    Kurczynski, Peter; Gawiser, Eric; Huynh, Minh; Ivison, Rob J.; Treister, Ezequiel; Smail, Ian; Blanc, Guillermo A.; Cardamone, Carolin N.; Greve, Thomas R.; Schinnerer, Eva; Van der Werf, Paul; Urry, Meg

    2012-05-10

    We determine star formation rates (SFRs) in a sample of color-selected, star-forming (sBzK) galaxies (K{sub AB} < 21.8) in the Extended Chandra Deep Field-South. To identify and avoid active galactic nuclei, we use X-ray, IRAC color, and IR/radio flux ratio selection methods. Photometric redshift-binned, average flux densities are measured with stacking analyses in Spitzer-MIPS IR, BLAST and APEX/LABOCA submillimeter, VLA and GMRT radio, and Chandra X-ray data. We include averages of aperture fluxes in MUSYC UBVRIz'JHK images to determine UV-through-radio spectral energy distributions. We determine the total IR luminosities and compare SFR calibrations from FIR, 24 {mu}m, UV, radio, and X-ray wavebands. We find consistency with our best estimator, SFR{sub IR+UV}, to within errors for the preferred radio SFR calibration. Our results imply that 24 {mu}m only and X-ray SFR estimates should be applied to high-redshift galaxies with caution. Average IR luminosities are consistent with luminous infrared galaxies. We find SFR{sub IR+UV} for our stacked sBzKs at median redshifts 1.4, 1.8, and 2.2 to be 55 {+-} 6 (random error), 74 {+-} 8, and 154 {+-} 17 M{sub Sun} yr{sup -1}, respectively, with additional systematic uncertainty of a factor of {approx}2.

  13. J-PLUS and the galaxy star formation rate in the local universe

    NASA Astrophysics Data System (ADS)

    Vilella, G.; Viironen, K.; López-Sanjuan, C.; Varela, J.; Cenarro, A. J.; J-PAS Team

    2015-05-01

    The Javalambre Physics of the Local Universe Survey (J-PLUS) is a large photometric survey that will cover ˜8000 deg^2 with a set of 5 broad filters (SDSS filter set) and 7 narrow ones. It will be carried out from the Observatorio Astrofísico de Javalambre (OAJ) at the Pico del Buitre, Teruel, Spain. In addition to its main goal, which is the photometric calibration of the J-PAS survey, it has been designed to acquire the Hα flux of the galaxies in the nearby Universe (z≤0.015) up to r˜23 (AB). In this poster we present a first approach to the methodology that will be used to obtain Hα fluxes from photometric data. We first explain different methodologies to recover this flux. To test these methodologies, we simulate observations of real star forming galaxies from SDSS spectra. We show that using the information of one or two broad filters and a narrow one would bias our results. To cope with that, we fit the whole observed spectral energy distribution to a simple stellar population template and isolate the excess of flux inside the Hα filter. This allows us to recover the desired flux with accuracy and without biases. With this information, the J-PLUS survey will allow us to reproduce the Hα luminosity function and derive the star formation rate of thousands of galaxies in the local universe.

  14. Thermal runaway features of large format prismatic lithium ion battery using extended volume accelerating rate calorimetry

    NASA Astrophysics Data System (ADS)

    Feng, Xuning; Fang, Mou; He, Xiangming; Ouyang, Minggao; Lu, Languang; Wang, Hao; Zhang, Mingxuan

    2014-06-01

    In this paper, the thermal runaway features of a 25 Ah large format prismatic lithium ion battery with Li(NixCoyMnz)O2 (NCM) cathode are evaluated using the extended volume-accelerating rate calorimetry (EV-ARC). 4 thermocouples are set at different positions of the battery. The temperature inside the battery is 870 °C or so, much higher than that outside the battery. The temperature difference is calculated from the recorded data. The temperature difference within the battery stays lower than 1 °C for 97% of the test period, while it rises to its highest, approximately 520 °C, when thermal runaway happens. The voltage of the battery is also measured during the test. It takes 15-40 s from the sharp drop of voltage to the instantaneous rise of temperature. Such a time interval is beneficial for early warning of the thermal runaway. Using a pulse charge/discharge profile, the internal resistance is derived from the quotient of the pulse voltage and the current during the ARC test. The internal resistance of the battery increases slowly from 20 mΩ to 60 mΩ before thermal runaway, while it rises to 370 mΩ when thermal runaway happens indicating the loss of the integrity of the separator or the battery swell.

  15. Star formation rate at multiple physical scales using CALIFA and TYPHOON data

    NASA Astrophysics Data System (ADS)

    Catalán-Torrecilla, C.; Gil de Paz, A.; Castillo-Morales, A.; Iglesias-Páramo, J.; Sánchez, S. F.; Madore, B. F.; Sturch, L.; CALIFA Collaboration

    2015-05-01

    Both good spatial resolution and sample statistics are key to properly determine (and calibrate) the star formation rate in galaxies. Nevertheless, having an extensive number of objects and high spatial resolution at the same time is a challenge. To address this issue we have combined a well-characterized sample of 380 nearby galaxies from the CALIFA IFS survey and HII Regions from Local Group galaxies using TYPHOON. Firstly, we derive integrated extinction-corrected Hα-based SFRs of 380 nearby galaxies in CALIFA. Then, we provide updated single and hybrid SFRs tracers using our integrated extinction-corrected Hα SFR as a reference. Despite the quality of our attenuation correction via Balmer decrement, this parameter remains one of the main sources of uncertainty in deriving the SFR from Hα. Other major sources of systematic error are the IMF and the escape fraction. To understand the role that the escape fraction plays in the SFR derivations we perform a detail analysis using high spatial resolution around individual HII regions. The aim is to study the Hα ionized gas and dust structure, and resolve the total population of young massive stars in these regions responsible for the ionizing emission. For that purpose, we use TYPHOON observations at the 6.5 m Baade Telescope in Las Campanas (Chile). TYPHOON is a newly methodology for producing highly resolved spectrophotometric datacubes in the optical range. This double approach will allow us to dramatically reduce the uncertainties in the spatially-resolved SFR in galaxies.

  16. ULTRAVIOLET+INFRARED STAR FORMATION RATES: HICKSON COMPACT GROUPS WITH SWIFT AND SPITZER

    SciTech Connect

    Tzanavaris, P.; Hornschemeier, A. E.; Immler, S.; Johnson, K. E.; Reines, A. E.; Gronwall, C.; Hoversten, E.; Charlton, J. C.

    2010-06-10

    We present Swift UVOT ultraviolet (UV; 1600-3000 A) data with complete three-band UV photometry for a sample of 41 galaxies in 11 nearby (<4500 km s{sup -1}) Hickson Compact Groups (HCGs) of galaxies. We use UVOT uvw2-band (2000 A) photometry to estimate the dust-unobscured component, SFR{sub UV}, of the total star formation rate, SFR{sub TOTAL}. We use Spitzer MIPS 24 {mu}m photometry to estimate SFR{sub IR}, the component of SFR{sub TOTAL} that suffers dust extinction in the UV and is re-emitted in the IR. By combining the two components, we obtain SFR{sub TOTAL} estimates for all HCG galaxies. We obtain total stellar mass, M {sub *}, estimates by means of Two Micron All Sky Survey K{sub s} -band luminosities, and use them to calculate specific star formation rates, SSFR {identical_to} SFR{sub TOTAL}/M {sub *}. SSFR values show a clear and significant bimodality, with a gap between low ({approx}<3.2 x 10{sup -11} yr{sup -1}) and high-SSFR ({approx_gt}1.2 x 10{sup -10} yr{sup -1}) systems. We compare this bimodality to the previously discovered bimodality in {alpha}{sub IRAC}, the MIR activity index from a power-law fit to the Spitzer IRAC 4.5-8 {mu}m data for these galaxies. We find that all galaxies with {alpha}{sub IRAC} {<=} 0 ( >0) are in the high- (low-) SSFR locus, as expected if high levels of star-forming activity power MIR emission from polycyclic aromatic hydrocarbon molecules and a hot dust continuum. Consistent with this finding, all elliptical/S0 galaxies are in the low-SSFR locus, while 22 out of 24 spirals/irregulars are in the high-SSFR locus, with two borderline cases. We further divide our sample into three subsamples (I, II, and III) according to decreasing H I richness of the parent galaxy group to which a galaxy belongs. Consistent with the SSFR and {alpha}{sub IRAC} bimodality, 12 out of 15 type I (11 out of 12 type III) galaxies are in the high- (low-) SSFR locus, while type II galaxies span almost the full range of SSFR values. We use the

  17. Ultraviolet+Infrared Star Formation Rates: Hickson Compact Groups with Swift and SPitzer

    NASA Technical Reports Server (NTRS)

    Tzanavaris, P.; Hornschemeier, A. E.; Gallagher, S. C.; Johnson, K. E.; Gronwall, C.; Immler, S.; Reines, A. E.; Hoversten, E.; Charlton, J. C.

    2010-01-01

    We present Swift UVOT ultraviolet (UV; 1600-3000 A) data with complete three-band UV photometry for a sample of 41 galaxies in 11 nearby (<4500 km/s) Hickson Compact Groups (HCGs) of galaxies. We use UVOT uvw2-band (2000A) photometry to estimate the dust-unobscured component, SFR(sub uv), of the total star formation rate, SFR(sub TOTAL). We use Spitzer MIPS 24 micron photometry to estimate SFR(sub IR), the component of SFR(sub TOTAL) that suffers dust extinction in the UV and is re-emitted in the IR. By combining the two components, we obtain SFR(sub TOTAL) estimates for all HCG galaxies. We obtain total stellar mass, M(sub *) estimates by means of Two Micron All Sky Survey K(sub s)-band luminosities, and use them to calculate specific star formation rates, SSFR is identical with SFR(sub TOTAL)/ M (sub *). SSFR values show a clear and significant bimodality, with a gap between low (approximately <3.2 x 10(exp -11) / yr) and high-SSFR (approximately > 1.2 x lO)exp -10)/yr) systems. We compare this bimodality to the previously discovered bimodality in alpha-IRAC, the MIR activity index from a power-law fit to the Spitzer IRAC 4.5-8 micron data for these galaxies. We find that all galaxies with alpha-IRAC <= 0 (> 0) are in the high- (low-) SSFR locus, as expected if high levels of star-forming activity power MIR emission from polycyclic aromatic hydrocarbon molecules and a hot dust continuum. Consistent with this finding, all elliptical/SO galaxies are in the low-SSFR locus, while 22 out of 24 spirals / irregulars are in the high-SSFR locus, with two borderline cases. We further divide our sample into three subsamples (I, II, and III) according to decreasing H I richness of the parent galaxy group to which a galaxy belongs. Consistent with the SSFR and alpha-IRAC bimodality, 12 out of 15 type I (11 out of 12 type III) galaxies are in the high- (low-) SSFR locus, while type II galaxies span almost the full range of SSFR values. We use the Spitzer Infrared Nearby Galaxy

  18. Polymorphism Analysis Reveals Reduced Negative Selection and Elevated Rate of Insertions and Deletions in Intrinsically Disordered Protein Regions

    PubMed Central

    Khan, Tahsin; Douglas, Gavin M.; Patel, Priyenbhai; Nguyen Ba, Alex N.; Moses, Alan M.

    2015-01-01

    Intrinsically disordered protein regions are abundant in eukaryotic proteins and lack stable tertiary structures and enzymatic functions. Previous studies of disordered region evolution based on interspecific alignments have revealed an increased propensity for indels and rapid rates of amino acid substitution. How disordered regions are maintained at high abundance in the proteome and across taxa, despite apparently weak evolutionary constraints, remains unclear. Here, we use single nucleotide and indel polymorphism data in yeast and human populations to survey the population variation within disordered regions. First, we show that single nucleotide polymorphisms in disordered regions are under weaker negative selection compared with more structured protein regions and have a higher proportion of neutral non-synonymous sites. We also confirm previous findings that nonframeshifting indels are much more abundant in disordered regions relative to structured regions. We find that the rate of nonframeshifting indel polymorphism in intrinsically disordered regions resembles that of noncoding DNA and pseudogenes, and that large indels segregate in disordered regions in the human population. Our survey of polymorphism confirms patterns of evolution in disordered regions inferred based on longer evolutionary comparisons. PMID:26047845

  19. The radio continuum-star formation rate relation in WSRT sings galaxies

    SciTech Connect

    Heesen, Volker; Brinks, Elias; Leroy, Adam K.; Heald, George; Braun, Robert; Bigiel, Frank; Beck, Rainer E-mail: v.heesen@soton.ac.uk E-mail: heald@astron.nl E-mail: bigiel@uni-heidelberg.de

    2014-05-01

    We present a study of the spatially resolved radio continuum-star formation rate (RC-SFR) relation using state-of-the-art star formation tracers in a sample of 17 THINGS galaxies. We use SFR surface density (Σ{sub SFR}) maps created by a linear combination of GALEX far-UV (FUV) and Spitzer 24 μm maps. We use RC maps at λλ22 and 18 cm from the WSRT SINGS survey and Hα emission maps to correct for thermal RC emission. We compare azimuthally averaged radial profiles of the RC and FUV/mid-IR (MIR) based Σ{sub SFR} maps and study pixel-by-pixel correlations at fixed linear scales of 1.2 and 0.7 kpc. The ratio of the integrated SFRs from the RC emission to that of the FUV/MIR-based SF tracers is R{sub int}=0.78±0.38, consistent with the relation by Condon. We find a tight correlation between the radial profiles of the radio and FUV/MIR-based Σ{sub SFR} for the entire extent of the disk. The ratio R of the azimuthally averaged radio to FUV/MIR-based Σ{sub SFR} agrees with the integrated ratio and has only quasi-random fluctuations with galactocentric radius that are relatively small (25%). Pixel-by-pixel plots show a tight correlation in log-log diagrams of radio to FUV/MIR-based Σ{sub SFR}, with a typical standard deviation of a factor of two. Averaged over our sample we find (Σ{sub SFR}){sub RC}∝(Σ{sub SFR}){sub hyb}{sup 0.63±0.25}, implying that data points with high Σ{sub SFR} are relatively radio dim, whereas the reverse is true for low Σ{sub SFR}. We interpret this as a result of spectral aging of cosmic-ray electrons (CREs), which are diffusing away from the star formation sites where they are injected into the interstellar medium. This is supported by our finding that the radio spectral index is a second parameter in pixel-by-pixel plots: those data points dominated by young CREs are relatively radio dim, while those dominated by old CREs are slightly more RC bright than what would be expected from a linear extrapolation. We studied the ratio R of

  20. Three-dimensional Hydrodynamic Simulations of Multiphase Galactic Disks with Star Formation Feedback. I. Regulation of Star Formation Rates

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Goo; Ostriker, Eve C.; Kim, Woong-Tae

    2013-10-01

    The energy and momentum feedback from young stars has a profound impact on the interstellar medium (ISM), including heating and driving turbulence in the neutral gas that fuels future star formation. Recent theory has argued that this leads to a quasi-equilibrium self-regulated state, and for outer atomic-dominated disks results in the surface density of star formation ΣSFR varying approximately linearly with the weight of the ISM (or midplane turbulent + thermal pressure). We use three-dimensional numerical hydrodynamic simulations to test the theoretical predictions for thermal, turbulent, and vertical dynamical equilibrium, and the implied functional dependence of ΣSFR on local disk properties. Our models demonstrate that all equilibria are established rapidly, and that the expected proportionalities between mean thermal and turbulent pressures and ΣSFR apply. For outer disk regions, this results in ΣSFR ∝ Σ&sqrt;{ρsd}, where Σ is the total gas surface density and ρsd is the midplane density of the stellar disk (plus dark matter). This scaling law arises because ρsd sets the vertical dynamical time in our models (and outer disk regions generally). The coefficient in the star formation law varies inversely with the specific energy and momentum yield from massive stars. We find proportions of warm and cold atomic gas, turbulent-to-thermal pressure, and mean velocity dispersions that are consistent with solar-neighborhood and other outer disk observations. This study confirms the conclusions of a previous set of simulations, which incorporated the same physics treatment but was restricted to radial-vertical slices through the ISM.

  1. THREE-DIMENSIONAL HYDRODYNAMIC SIMULATIONS OF MULTIPHASE GALACTIC DISKS WITH STAR FORMATION FEEDBACK. I. REGULATION OF STAR FORMATION RATES

    SciTech Connect

    Kim, Chang-Goo; Ostriker, Eve C.; Kim, Woong-Tae E-mail: eco@astro.princeton.edu

    2013-10-10

    The energy and momentum feedback from young stars has a profound impact on the interstellar medium (ISM), including heating and driving turbulence in the neutral gas that fuels future star formation. Recent theory has argued that this leads to a quasi-equilibrium self-regulated state, and for outer atomic-dominated disks results in the surface density of star formation Σ{sub SFR} varying approximately linearly with the weight of the ISM (or midplane turbulent + thermal pressure). We use three-dimensional numerical hydrodynamic simulations to test the theoretical predictions for thermal, turbulent, and vertical dynamical equilibrium, and the implied functional dependence of Σ{sub SFR} on local disk properties. Our models demonstrate that all equilibria are established rapidly, and that the expected proportionalities between mean thermal and turbulent pressures and Σ{sub SFR} apply. For outer disk regions, this results in Σ{sub SFR}∝Σ√(ρ{sub sd}), where Σ is the total gas surface density and ρ{sub sd} is the midplane density of the stellar disk (plus dark matter). This scaling law arises because ρ{sub sd} sets the vertical dynamical time in our models (and outer disk regions generally). The coefficient in the star formation law varies inversely with the specific energy and momentum yield from massive stars. We find proportions of warm and cold atomic gas, turbulent-to-thermal pressure, and mean velocity dispersions that are consistent with solar-neighborhood and other outer disk observations. This study confirms the conclusions of a previous set of simulations, which incorporated the same physics treatment but was restricted to radial-vertical slices through the ISM.

  2. Current denudation rates in dolostone karst from central Spain: Implications for the formation of unroofed caves

    NASA Astrophysics Data System (ADS)

    Krklec, Kristina; Domínguez-Villar, David; Carrasco, Rosa M.; Pedraza, Javier

    2016-07-01

    depth, we consider that this is a more reliable denudation rate for the studied location during the studied period. The calculated weathering rate suggests that denudation has a limited contribution to the thinning of bedrock over caves at this site. Therefore, we consider that the formation of unroofed caves in this region most likely results from the thinning of bedrock cover over caves due to collapse of blocks from their ceilings.

  3. Global analysis of the root hair morphogenesis transcriptome reveals new candidate genes involved in root hair formation in barley.

    PubMed

    Kwasniewski, Miroslaw; Janiak, Agnieszka; Mueller-Roeber, Bernd; Szarejko, Iwona

    2010-09-01

    Root hairs are long tubular outgrowths of specialized root epidermal cells that play an important role in plant nutrition and water uptake. They are also an important model in studies of higher plant cell differentiation. In contrast to the model dicot Arabidopsis thaliana, currently very little is known about the genetic and molecular basis of root hair formation in monocots, including major cereals. To elucidate candidate genes controlling this developmental process in barley, we took advantage of the recently established Affymetrix GeneChip Barley1 Genome Array to carry out global transcriptome analyses of hairless and root hair primordia-forming roots of two barely mutant lines. Expression profiling of the root-hairless mutant rhl1.a and its wild type parent variety 'Karat' revealed 10 genes potentially involved in the early step of root hair formation in barley. Differential expression of all identified genes was confirmed by quantitative reverse transcription-polymerase chain reaction. The genes identified encode proteins associated with the cell wall and membranes, including one gene for xyloglucan endotransglycosylase, three for peroxidase enzymes and five for arabinogalactan protein, extensin, leucine-rich-repeat protein, phosphatidylinositol phosphatidylcholine transfer protein and a RhoGTPase GDP dissociation inhibitor, respectively. The molecular function of one gene is unknown at present. The expression levels of these genes were strongly reduced in roots of the root-hairless mutant rhl1.a compared to the parent variety, while expression of all 10 genes was similar in another mutant, i.e. rhp1.b, that has lost its ability to develop full root hairs but still forms hairs blocked at the primordium stage, and its wild type relative. This clearly indicates that the new genes identified are involved in the initiation of root hair morphogenesis in barley. PMID:20388575

  4. Comparative genomic and transcriptomic analysis revealed genetic characteristics related to solvent formation and xylose utilization in Clostridium acetobutylicum EA 2018

    PubMed Central

    2011-01-01

    Background Clostridium acetobutylicum, a gram-positive and spore-forming anaerobe, is a major strain for the fermentative production of acetone, butanol and ethanol. But a previously isolated hyper-butanol producing strain C. acetobutylicum EA 2018 does not produce spores and has greater capability of solvent production, especially for butanol, than the type strain C. acetobutylicum ATCC 824. Results Complete genome of C. acetobutylicum EA 2018 was sequenced using Roche 454 pyrosequencing. Genomic comparison with ATCC 824 identified many variations which may contribute to the hyper-butanol producing characteristics in the EA 2018 strain, including a total of 46 deletion sites and 26 insertion sites. In addition, transcriptomic profiling of gene expression in EA 2018 relative to that of ATCC824 revealed expression-level changes of several key genes related to solvent formation. For example, spo0A and adhEII have higher expression level, and most of the acid formation related genes have lower expression level in EA 2018. Interestingly, the results also showed that the variation in CEA_G2622 (CAC2613 in ATCC 824), a putative transcriptional regulator involved in xylose utilization, might accelerate utilization of substrate xylose. Conclusions Comparative analysis of C. acetobutylicum hyper-butanol producing strain EA 2018 and type strain ATCC 824 at both genomic and transcriptomic levels, for the first time, provides molecular-level understanding of non-sporulation, higher solvent production and enhanced xylose utilization in the mutant EA 2018. The information could be valuable for further genetic modification of C. acetobutylicum for more effective butanol production. PMID:21284892

  5. Site-directed Mutagenesis Reveals Regions Implicated in the Stability and Fiber Formation of Human λ3r Light Chains*

    PubMed Central

    Villalba, Miryam I.; Canul-Tec, Juan C.; Luna-Martínez, Oscar D.; Sánchez-Alcalá, Rosalba; Olamendi-Portugal, Timoteo; Rudiño-Piñera, Enrique; Rojas, Sonia; Sánchez-López, Rosana; Fernández-Velasco, Daniel A.; Becerril, Baltazar

    2015-01-01

    Light chain amyloidosis (AL) is a disease that affects vital organs by the fibrillar aggregation of monoclonal light chains. λ3r germ line is significantly implicated in this disease. In this work, we contrasted the thermodynamic stability and aggregation propensity of 3mJL2 (nonamyloidogenic) and 3rJL2 (amyloidogenic) λ3 germ lines. Because of an inherent limitation (extremely low expression), Cys at position 34 of the 3r germ line was replaced by Tyr reaching a good expression yield. A second substitution (W91A) was introduced in 3r to obtain a better template to incorporate additional mutations. Although the single mutant (C34Y) was not fibrillogenic, the second mutation located at CDR3 (W91A) induced fibrillogenesis. We propose, for the first time, that CDR3 (position 91) affects the stability and fiber formation of human λ3r light chains. Using the double mutant (3rJL2/YA) as template, other variants were constructed to evaluate the importance of those substitutions into the stability and aggregation propensity of λ3 light chains. A change in position 7 (P7D) boosted 3rJL2/YA fibrillogenic properties. Modification of position 48 (I48M) partially reverted 3rJL2/YA fibril aggregation. Finally, changes at positions 8 (P8S) or 40 (P40S) completely reverted fibril formation. These results confirm the influential roles of N-terminal region (positions 7 and 8) and the loop 40–60 (positions 40 and 48) on AL. X-ray crystallography revealed that the three-dimensional topology of the single and double λ3r mutants was not significantly altered. This mutagenic approach helped to identify key regions implicated in λ3 AL. PMID:25505244

  6. Offset of Latest Pleistocene Shoreface Reveals Slip Rate on the Hosgri Strike-Slip Fault, Offshore Central California

    NASA Astrophysics Data System (ADS)

    Johnson, S. Y.; Hartwell, S. R.; Dartnell, P.

    2014-12-01

    The Hosgri fault is the southern part of the regional Hosgri-San Gregorio dextral strike-slip fault system, which extends primarily in the offshore region for about 400 km in central California. Between Morro Bay and San Simeon, high-resolution multibeam bathymetry reveals that the eastern strand of the Hosgri fault is crossed by a ~265-m-wide slope interpreted as the shoreface of a relict sand spit that formed during a period of relatively slower sea-level rise (Younger Dryas stadial) in the latest Pleistocene. This sand spit crossed an embayment and connected a western fault-bounded bedrock peninsula and an eastern bedrock highland, a paleogeography similar to modern geomorphology along coastal segments of the San Andreas fault. Detailed analysis of the relict shoreface with slope profiles and slope maps indicates a lateral slip rate of 2.6 ± 0.9 mm/yr. Because the Hosgri fault locally includes an active western strand, and regionally converges with several other faults, this slip rate should be considered a minimum for the Hosgri fault in central California and should not be applied for the entire Hosgri-San Gregorio fault system. This slip rate indicates that the Hosgri system takes up the largest share of the strike-slip fault budget and is the most active strike-slip fault west of the San Andreas fault in central California. This result further demonstrates the value and potential of high-resolution bathymetry in earthquake-hazard characterization of active offshore faults.

  7. Mechanical response and microcrack formation in a fine-grained duplex TiAl at different strain rates and temperatures

    SciTech Connect

    Jin, Z.; Cady, C.; Gray, G.T. III; Kim, Y.-W.

    1996-10-01

    Compressive behavior of this alloy was studied at strain rates of 0. 001 and 2000 sec{sup -1} and temperatures from -196 C to 1200 C. Temperature dependence of yield stress was found to depend on strain rate: At the quasi-static strain rate, 0.001 sec{sup -1}, the yield stress decreases with temperature with a plateau between 200 and 800 C. At the high strain rate, 2000 sec{sup -1}, the yield stress exhibits a positive temperature dependence above 600 C. Strain hardening rate decreases dramatically with temperature in the very low and high temperature regions with a plateau at intermediate temperatures for both strain rates. As the strain rate increases, the strain hardening rate plateaus extended to higher temperatures. The strain rate sensitivity increases slightly with temperature (but less than 0.1) for strain rates above 0.001 sec{sup -1}. However, at a strain rate of 0.001 sec{sup -1}, there is a dramatic increase in the strain rate sensitivity with temperature; above 1100 C, the rate sensitivity becomes much larger. Microcracks occurring in grain interiors and at grain boundaries were observed at all strain rates and temperatures. Formation and distribution of microcracks were found to vary depending on strain rate and deformation temperature.

  8. Star Formation Rates in Resolved Galaxies: Calibrations with Near- and Far-infrared Data for NGC 5055 and NGC 6946

    NASA Astrophysics Data System (ADS)

    Li, Yiming; Crocker, Alison F.; Calzetti, Daniela; Wilson, Christine D.; Kennicutt, Robert C.; Murphy, Eric J.; Brandl, Bernhard R.; Draine, B. T.; Galametz, M.; Johnson, B. D.; Armus, L.; Gordon, K. D.; Croxall, K.; Dale, D. A.; Engelbracht, C. W.; Groves, B.; Hao, C.-N.; Helou, G.; Hinz, J.; Hunt, L. K.; Krause, O.; Roussel, H.; Sauvage, M.; Smith, J. D. T.

    2013-05-01

    We use the near-infrared Brγ hydrogen recombination line as a reference star formation rate (SFR) indicator to test the validity and establish the calibration of the Herschel/PACS 70 μm emission as a SFR tracer for sub-galactic regions in external galaxies. Brγ offers the double advantage of directly tracing ionizing photons and of being relatively insensitive to the effects of dust attenuation. For our first experiment, we use archival Canada-France-Hawaii Telescope Brγ and Ks images of two nearby galaxies: NGC 5055 and NGC 6946, which are also part of the Herschel program KINGFISH (Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel). We use the extinction corrected Brγ emission to derive the SFR(70) calibration for H II regions in these two galaxies. A comparison of the SFR(70) calibrations at different spatial scales, from 200 pc to the size of the whole galaxy, reveals that about 50% of the total 70 μm emission is due to dust heated by stellar populations that are unrelated to the current star formation. We use a simple model to qualitatively relate the increase of the SFR(70) calibration coefficient with decreasing region size to the star formation timescale. We provide a calibration for an unbiased SFR indicator that combines the observed Hα with the 70 μm emission, also for use in H II regions. We briefly analyze the PACS 100 and 160 μm maps and find that longer wavelengths are not as good SFR indicators as 70 μm, in agreement with previous results. We find that the calibrations show about 50% difference between the two galaxies, possibly due to effects of inclination. Based on observations obtained with WIRCam, a joint project of CFHT, Taiwan, Korea, Canada, France, and the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

  9. A Multiwavelength Approach to the Star Formation Rate Estimation in Galaxies at Intermediate Redshifts

    NASA Astrophysics Data System (ADS)

    Cardiel, N.; Elbaz, D.; Schiavon, R. P.; Willmer, C. N. A.; Koo, D. C.; Phillips, A. C.; Gallego, J.

    2003-02-01

    We use a sample of seven starburst galaxies at intermediate redshifts (z~0.4 and 0.8) with observations ranging from the observed ultraviolet to 1.4 GHz, to compare the star formation rate (SFR) estimators that are used in the different wavelength regimes. We find that extinction-corrected Hα underestimates the SFR, and the degree of this underestimation increases with the infrared luminosity of the galaxies. Galaxies with very different levels of dust extinction as measured with SFRIR/SFR(Hα, uncorrected for extinction) present a similar attenuation A[Hα], as if the Balmer lines probed a different region of the galaxy than the one responsible for the bulk of the IR luminosity for large SFRs. In addition, SFR estimates derived from [O II] λ3727 match very well those inferred from Hα after applying the metallicity correction derived from local galaxies. SFRs estimated from the UV luminosities show a dichotomic behavior, similar to that previously reported by other authors in galaxies at z<~0.4. Here we extend this result up to z~0.8. Finally, one of the studied objects is a luminous compact galaxy (LCG) that may be suffering similar dust-enshrouded star formation episodes. These results highlight the relevance of quantifying the actual LIR of LCGs, as well as that of a much larger and generic sample of luminous infrared galaxies, which will be possible after the launch of SIRTF. Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Based in part on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Based in part on

  10. Rate of formation and dissolution of mercury sulfide nanoparticles: The dual role of natural organic matter

    USGS Publications Warehouse

    Slowey, Aaron J.

    2010-01-01

    Mercury is a global contaminant of concern due to its transformation by microorganisms to form methylmercury, a toxic species that accumulates in biological tissues. The effect of dissolved organic matter (DOM) isolated from natural waters on reactions between mercury(II) (Hg) and sulfide (S(-II)) to form HgS(s) nanoparticles across a range of Hg and S(-II) concentrations was investigated. Hg was equilibrated with DOM, after which S(-II) was added. Dissolved Hg (Hgaq) was periodically quantified using ultracentrifugation and chemical analysis following the addition of S(-II). Particle size and identity were determined using dynamic light scattering and X-ray absorption spectroscopy. S(-II) reacts with Hg to form 20 to 200nm aggregates consisting of 1-2 nm HgS(s) subunits that are more structurally disordered than metacinnabar in the presence of 2 x 10-9 to 8 x 10-6M Hg and 10 (mg C)L-1 DOM. Some of the HgS(s) nanoparticle aggregates are subsequently dissolved by DOM and (re)precipitated by S(-II) over periods of hours to days. At least three fractions of Hg-DOM species were observed with respect to reactivity toward S(-II): 0.3 μmol reactive Hg per mmol C (60 percent), 0.1 μmol per mmol C (20 percent) that are kinetically hindered, and another 0.1 μmol Hg per mmol C (20 percent) that are inert to reaction with S(-II). Following an initial S(-II)-driven precipitation of HgS(s), HgS(s) was dissolved by DOM or organic sulfur compounds. HgS(s) formation during this second phase was counterintuitively favored by lower S(-II) concentrations, suggesting surface association of DOM moieties that are less capable of dissolving HgS(s). DOM partially inhibits HgS(s) formation and mediates reactions between Hg and S(-II) such that HgS(s) is susceptible to dissolution. These findings indicate that Hg accessibility to microorganisms could be controlled by kinetic (intermediate) species in the presence of S(-II) and DOM, undermining the premise that equilibrium Hg species

  11. Rates and Properties of Type Ia Supernovae as a Function of Mass and Star Formation in Their Host Galaxies

    NASA Astrophysics Data System (ADS)

    Sullivan, M.; Le Borgne, D.; Pritchet, C. J.; Hodsman, A.; Neill, J. D.; Howell, D. A.; Carlberg, R. G.; Astier, P.; Aubourg, E.; Balam, D.; Basa, S.; Conley, A.; Fabbro, S.; Fouchez, D.; Guy, J.; Hook, I.; Pain, R.; Palanque-Delabrouille, N.; Perrett, K.; Regnault, N.; Rich, J.; Taillet, R.; Baumont, S.; Bronder, J.; Ellis, R. S.; Filiol, M.; Lusset, V.; Perlmutter, S.; Ripoche, P.; Tao, C.

    2006-09-01

    We show that Type Ia supernovae (SNe Ia) are formed within both very young and old stellar populations, with observed rates that depend on the stellar mass and mean star formation rates (SFRs) of their host galaxies. Models in which the SN Ia rate depends solely on host galaxy stellar mass are ruled out with >99% confidence. Our analysis is based on 100 spectroscopically confirmed SNe Ia, plus 24 photometrically classified events, all from the Supernova Legacy Survey (SNLS) and distributed over 0.2rate per unit mass is proportional to the specific SFR of the parent galaxies-more vigorously star-forming galaxies host more SNe Ia per unit stellar mass, broadly equivalent to the trend of increasing SN Ia rate in later type galaxies seen in the local universe. Following earlier suggestions for a simple ``two-component'' model approximating the SN Ia rate, we find bivariate linear dependencies of the SN Ia rate on both the stellar masses and the mean SFRs of the host systems. We find that the SN Ia rate can be well represented as the sum of 5.3+/-1.1×10-14 SNe yr-1 Msolar-1 and 3.9+/-0.7×10-4 SNe yr-1 (Msolar yr-1)-1 of star formation. We also demonstrate a dependence of distant SN Ia light-curve shapes on star formation in the host galaxy, similar to trends observed locally. Passive galaxies, with no star formation, preferentially host faster declining/dimmer SNe Ia, while brighter events are found in systems with ongoing star formation.

  12. GAMMA-RAY BURST AND STAR FORMATION RATES: THE PHYSICAL ORIGIN FOR THE REDSHIFT EVOLUTION OF THEIR RATIO

    SciTech Connect

    Trenti, Michele; Perna, Rosalba; Tacchella, Sandro

    2013-08-20

    Gamma-ray bursts (GRBs) and galaxies at high redshift represent complementary probes of the star formation history of the universe. In fact, both the GRB rate and the galaxy luminosity density are connected to the underlying star formation. Here, we combine a star formation model for the evolution of the galaxy luminosity function from z = 0 to z = 10 with a metallicity-dependent efficiency for GRB formation to simultaneously predict the comoving GRB rate. Our model sheds light on the physical origin of the empirical relation often assumed between GRB rate and luminosity density-derived star formation rate: n-dot{sub GRB}(z)={epsilon}(z) Multiplication-Sign {rho}-dot{sup *}{sub obs}(z), with {epsilon}(z){proportional_to}(1 + z){sup 1.2}. At z {approx}< 4, {epsilon}(z) is dominated by the effects of metallicity evolution in the GRB efficiency. Our best-fitting model only requires a moderate preference for low-metallicity, that is a GRB rate per unit stellar mass about four times higher for log (Z/Z{sub Sun }) < -3 compared to log (Z/Z{sub Sun }) > 0. Models with total suppression of GRB formation at log (Z/Z{sub Sun }) {approx}> 0 are disfavored. At z {approx}> 4, most of the star formation happens in low-metallicity hosts with nearly saturated efficiency of GRB production per unit stellar mass. However, at the same epoch, galaxy surveys miss an increasing fraction of the predicted luminosity density because of flux limits, driving an accelerated evolution of {epsilon}(z) compared to the empirical power-law fit from lower z. Our findings are consistent with the non-detections of GRB hosts in ultradeep imaging at z > 5, and point toward current galaxy surveys at z > 8 only observing the top 15%-20% of the total luminosity density.

  13. Characterization and refinement of carbide coating formation rates and dissolution kinetics in the Ta-C system

    SciTech Connect

    Rodriguez, P.J.

    1996-10-01

    The interaction between carbide coating formation rates and dissolution kinetics in the tantalum-carbon system was investigated. The research was driven by the need to characterize carbide coating formation rates. The characterization of the carbide coating formation rates was required to engineer an optimum processing scheme for the fabrication of the ultracorrosion-resistant composite, carbon-saturated tantalum. A packed-bed carburization process was successfully engineered and employed. The packed-bed carburization process produced consistent, predictable, and repeatable carbide coatings. A digital imaging analysis measurement process for accurate and consistent measurement of carbide coating thicknesses was developed. A process for removing the chemically stable and extremely hard tantalum-carbide coatings was also developed in this work.

  14. Rate of Iron Transfer Through the Horse Spleen Ferritin Shell Determined by the Rate of Formation of Prussian Blue and Fe-desferrioxamine Within the Ferritin Cavity

    NASA Technical Reports Server (NTRS)

    Zhang, Bo; Watt, Richard K.; Galvez, Natividad; Dominquez-Vera, Jose M.; Watt, Gerald D.

    2005-01-01

    Iron (2+ and 3+) is believed to transfer through the three-fold channels in the ferritin shell during iron deposition and release in animal ferritins. However, the rate of iron transit in and out through these channels has not been reported. The recent synthesis of [Fe(CN)(sub 6)](3-), Prussian Blue (PB) and desferrioxamine (DES) all trapped within the horse spleen ferritin (HoSF) interior makes these measurements feasible. We report the rate of Fe(2+) penetrating into the ferritin interior by adding external Fe(2+) to [Fe(CN)(sub 6)](3-) encapsulated in the HoSF interior and measuring the rate of formation of the resulting encapsulated PB. The rate at which Fe(2+) reacts with [Fe(CN)(sub 6)](3-) in the HoSF interior is much slower than the formation of free PB in solution and is proceeded by a lag period. We assume this lag period and the difference in rate represent the transfer of Fe(2+) through the HoSF protein shell. The calculated diffusion coefficient, D approx. 5.8 x 10(exp -20) square meters per second corresponds to the measured lag time of 10-20 s before PB forms within the HoSF interior. The activation energy for Fe(2+) transfer from the outside solution through the protein shell was determined to be 52.9 kJ/mol by conducting the reactions at 10 to approximately 40 C. The reaction of Fe(3+) with encapsulated [Fe(CN)6](4-) also readily forms PB in the HoSF interior, but the rate is faster than the corresponding Fe(2+) reaction. The rate for Fe(3+) transfer through the ferritin shell was confirmed by measuring the rate of the formation of Fe-DES inside HoSF and an activation energy of 58.4 kJ/mol was determined. An attempt was made to determine the rate of iron (2+ and 3+) transit out from the ferritin interior by adding excess bipyridine or DES to PB trapped within the HoSF interior. However, the reactions are slow and occur at almost identical rates for free and HoSF-encapsulated PB, indicating that the transfer of iron from the interior through the

  15. The Star Formation Rate Density of the Universe at z = 0.24 and 0.4 from Halpha

    NASA Astrophysics Data System (ADS)

    Pascual, S.

    2005-01-01

    Knowledge of both the global star formation history of the universe and the nature of individual star-forming galaxies at different look-back times is essential to our understanding of galaxy formation and evolution. Deep redshift surveys suggest star-formation activity increases by an order of magnitude from z = 0 to ~1. As a direct test of whether substantial evolution in star-formation activity has occurred, we need to measure the star formation rate (SFR) density and the properties of the corresponding star-forming galaxy populations at different redshifts, using similar techniques. The main goal of this work is to extend the Universidad Complutense de Madrid (UCM) survey of emission-line galaxies to higher redshifts. (continues)

  16. Structural Analysis using SHALiPE to Reveal RNA G-Quadruplex Formation in Human Precursor MicroRNA.

    PubMed

    Kwok, Chun Kit; Sahakyan, Aleksandr B; Balasubramanian, Shankar

    2016-07-25

    RNA G-quadruplex (rG4) structures are of fundamental importance to biology. A novel approach is introduced to detect and structurally map rG4s at single-nucleotide resolution in RNAs. The approach, denoted SHALiPE, couples selective 2'-hydroxyl acylation with lithium ion-based primer extension, and identifies characteristic structural fingerprints for rG4 mapping. We apply SHALiPE to interrogate the human precursor microRNA 149, and reveal the formation of an rG4 structure in this non-coding RNA. Additional analyses support the SHALiPE results and uncover that this rG4 has a parallel topology, is thermally stable, and is conserved in mammals. An in vitro Dicer assay shows that this rG4 inhibits Dicer processing, supporting the potential role of rG4 structures in microRNA maturation and post-transcriptional regulation of mRNAs. PMID:27355429

  17. Super resolution microscopy is poised to reveal new insights into the formation and maturation of dendritic spines

    PubMed Central

    Robinson, Cristina M.; Patel, Mikin R.; Webb, Donna J.

    2016-01-01

    Dendritic spines and synapses are critical for neuronal communication, and they are perturbed in many neurological disorders; however, the study of these structures in living cells has been hindered by their small size. Super resolution microscopy, unlike conventional light microscopy, is diffraction unlimited and thus is well suited for imaging small structures, such as dendritic spines and synapses. Super resolution microscopy has already revealed important new information about spine and synapse morphology, actin remodeling, and nanodomain composition in both healthy cells and diseased states. In this review, we highlight the advancements in probes that make super resolution more amenable to live-cell imaging of spines and synapses. We also discuss recent data obtained by super resolution microscopy that has advanced our knowledge of dendritic spine and synapse structure, organization, and dynamics in both healthy and diseased contexts. Finally, we propose a series of critical questions for understanding spine and synapse formation and maturation that super resolution microscopy is poised to answer. PMID:27408691

  18. Hydroxyl radical in/on illuminated polar snow: formation rates, lifetimes, and steady-state concentrations

    NASA Astrophysics Data System (ADS)

    Chen, Zeyuan; Chu, Liang; Galbavy, Edward S.; Ram, Keren; Anastasio, Cort

    2016-08-01

    While the hydroxyl radical (OH) in the snowpack is likely a dominant oxidant for organic species and bromide, little is known about the kinetics or steady-state concentrations of OH on/in snow and ice. Here we measure the formation rate, lifetime, and concentration of OH for illuminated polar snow samples studied in the laboratory and in the field. Laboratory studies show that OH kinetics and steady-state concentrations are essentially the same for a given sample studied as ice and liquid; this is in contrast to other photooxidants, which show a concentration enhancement in ice relative to solution as a result of kinetic differences in the two phases. The average production rate of OH in samples studied at Summit, Greenland, is 5 times lower than the average measured in the laboratory, while the average OH lifetime determined in the field is 5 times higher than in the laboratory. These differences indicate that the polar snows we studied in the laboratory are affected by contamination, despite significant efforts to prevent this; our results suggest similar contamination may be a widespread problem in laboratory studies of ice chemistry. Steady-state concentrations of OH in clean snow studied in the field at Summit, Greenland, range from (0.8 to 3) × 10-15 M, comparable to values reported for midlatitude cloud and fog drops, rain, and deliquesced marine particles, even though impurity concentrations in the snow samples are much lower. Partitioning of firn air OH to the snow grains will approximately double the steady-state concentration of snow-grain hydroxyl radical, leading to an average [OH] in near-surface, summer Summit snow of approximately 4 × 10-15 M. At this concentration, the OH-mediated lifetimes of organics and bromide in Summit snow grains are approximately 3 days and 7 h, respectively, suggesting that hydroxyl radical is a major

  19. Formation rate of ammonium nitrate in the off-gas line of SRAT and SME in DWPF

    SciTech Connect

    Lee, L.

    1992-02-25

    A mathematical model for the formation rate of ammonium nitrate in the off-gas line of the Sludge Receipt and Adjustment Tank (SRAT) and the Slurry Mixed Evaporator (SME) in DWPF has been developed. The formation rate of ammonium nitrate in the off-gas line depends on pH, temperature, volume and total concentration of ammonia and ammonium ion. Based on a typical SRAT and SME cycle in DWPF, this model predicts the SRAT contributes about 50 lbs of ammonium nitrate while SME contributes about 60 lbs of ammonium nitrate to the off-gas line.

  20. On the Reversal of Star formation Rate-Density Relation at z = 1: Insights from Simulations

    NASA Astrophysics Data System (ADS)

    Tonnesen, Stephanie; Cen, Renyue

    2014-06-01

    Recent surveys have found a reversal of the star formation rate (SFR)-density relation at z = 1 from that at z = 0, while the sign of the slope of the color-density relation remains unchanged. We use adaptive mesh refinement cosmological hydrodynamic simulations of a 21 × 24 × 20 h -3 Mpc3 region to examine the SFR-density and color-density relations of galaxies at z = 0 and z = 1. The local environmental density is defined by the dark matter mass in spheres of radius 1 h -1 Mpc, and we probe two decades of environmental densities. Our simulations produce a large increase of SFR with density at z = 1, as in the Elbaz et al. observations. We also find a significant evolution to z = 0, where the SFR-density relation is much flatter. The simulated color-density relation is consistent from z = 1 to z = 0, in agreement with observations. We find that the increase in SFR with local density at z = 1 is due to a growing population of star-forming galaxies in higher-density environments. At z = 0 and z = 1 both the SFR and cold gas mass are correlated with the galaxy halo mass, and therefore the correlation between median halo mass and local density is an important cause of the SFR-density relation at both redshifts. However, at z = 0 the local density on 1 h -1 Mpc scales affects galaxy SFRs as much as halo mass. Finally, we find indications that while at z = 0 high-density environments depress galaxy SFRs, at z = 1 high-density environments tend to increase SFRs.

  1. Observational evidence for the evolution of nuclear metallicity and star formation rate with the merger stage

    NASA Astrophysics Data System (ADS)

    Guo, Rui; Hao, Cai-Na; Xia, Xiao-Yang; Wei, Peng; Guo, Xin

    2016-07-01

    We investigate the evolution of nuclear gas-phase oxygen abundance and star formation rate (SFR) of local far-infrared selected star-forming galaxies along the merger sequence, as traced by their optical morphologies. The sample was drawn from a cross-correlation analysis of the IRAS Point Source Catalog Redshift Survey and 1 Jy ultraluminous infrared galaxy sample with the Sloan Digital Sky Survey Data Release 7 database. The investigation is done by comparing our sample to a control sample matched in the normalized redshift distribution in two diagnostics, which are the nuclear gas-phase metallicity vs. stellar mass and the nuclear SFR vs. stellar mass diagrams. Galaxies with different morphological types show different mass-metallicity relations (MZRs). Compared to the MZR defined by the control sample, isolated spirals have comparable metallicities with the control sample at a given stellar mass. Spirals in pairs and interacting galaxies with projected separations of r p > 20 kpc show a mild metallicity dilution of 0.02–0.03 dex. Interacting galaxies with r p < 20 kpc, pre-mergers and advanced mergers are underabundant by ∼ 0.06, ∼ 0.05 and ∼ 0.04 dex, respectively. This shows an evolutionary trend that the metallicity is increasingly depressed as the merging proceeds and it is diluted most dramatically when two galaxies are closely interacting. Afterwards, the interstellar medium (ISM) is enriched when the galaxies coalesce. This is the first time that such ISM enrichment at the final coalescence stage has been observed, which demonstrates the importance of supernova explosions in affecting the nuclear metallicity. Moreover, the central SFR enhancement relative to the control sample evolves simultaneously with the nuclear gas-phase oxygen abundance. Our results support the predictions from numerical simulations.

  2. Peroxy radical concentration and ozone formation rate at a rural site in the southeastern United States

    NASA Astrophysics Data System (ADS)

    Kleinman, Lawrence; Lee, Yin-Nan; Springston, Stephen R.; Lee, Jai H.; Nunnermacker, Linda; Weinstein-Lloyd, Judith; Zhou, Xianliang; Newman, Leonard

    1995-04-01

    As part of the Southern Oxidants Study, Brookhaven National Laboratory operated an intensive measurement site near Metter, Georgia, during parts of the summers of 1991 and 1992. Measurements were made of photochemically active trace gases and meteorological parameters relevant to determining causes for elevated ambient ozone concentration. The 1992 data set was used to calculate peroxy radical concentration and ozone formation rate based on determining the departure from the photostationary state (PSS) and based on a radical budget equation, such as applied previously to the 1991 data set. Averaged over the 28-day experimental period, we find maximum radical production occurring near noon at 2.5 ppb h-1, maximum peroxy radical concentration also occurring near noon at 80 ppt, and maximum ozone production of 8 ppb h-1 occurring near 1000 EST. Ozone photolysis accounts for 55% of radical production, HCHO and other carbonyl compounds about 40%. The radical budget and PSS methods depend in different ways on atmospheric photochemistry and a comparison between them affords a test of our understanding of the photochemical production of O3. We find that these methods agree to the extent expected based on uncertainty estimates. For the data set as a whole, the median estimate for fractional error in hourly average peroxy radical concentration determined from the radical budget method is approximately 30% and from the PSS method, 50%. Error estimates for the PSS method are highly variable, becoming infinite as peroxy radical concentration approaches zero. This behavior can be traced back to the difference form of the PSS equations. To conduct a meaningful comparison between the methods, the data set was segregated into subsets based on PSS uncertainty estimates. For the low-uncertainty subset, consisting of a third of the whole data set, we find that the ratio of peroxy radical concentration predicted from the PSS method to that predicted from the radical budget method to be

  3. The density structure and star formation rate of non-isothermal polytropic turbulence

    NASA Astrophysics Data System (ADS)

    Federrath, Christoph; Banerjee, Supratik

    2015-04-01

    The interstellar medium of galaxies is governed by supersonic turbulence, which likely controls the star formation rate (SFR) and the initial mass function (IMF). Interstellar turbulence is non-universal, with a wide range of Mach numbers, magnetic fields strengths and driving mechanisms. Although some of these parameters were explored, most previous works assumed that the gas is isothermal. However, we know that cold molecular clouds form out of the warm atomic medium, with the gas passing through chemical and thermodynamic phases that are not isothermal. Here we determine the role of temperature variations by modelling non-isothermal turbulence with a polytropic equation of state (EOS), where pressure and temperature are functions of gas density, P˜ ρ ^Γ, T ˜ ρΓ - 1. We use grid resolutions of 20483 cells and compare polytropic exponents Γ = 0.7 (soft EOS), Γ = 1 (isothermal EOS) and Γ = 5/3 (stiff EOS). We find a complex network of non-isothermal filaments with more small-scale fragmentation occurring for Γ < 1, while Γ > 1 smoothes out density contrasts. The density probability distribution function (PDF) is significantly affected by temperature variations, with a power-law tail developing at low densities for Γ > 1. In contrast, the PDF becomes closer to a lognormal distribution for Γ ≲ 1. We derive and test a new density variance-Mach number relation that takes Γ into account. This new relation is relevant for theoretical models of the SFR and IMF, because it determines the dense gas mass fraction of a cloud, from which stars form. We derive the SFR as a function of Γ and find that it decreases by a factor of ˜5 from Γ = 0.7 to 5/3.

  4. Brightest group galaxies: stellar mass and star formation rate (paper I)

    NASA Astrophysics Data System (ADS)

    Gozaliasl, Ghassem; Finoguenov, Alexis; Khosroshahi, Habib G.; Mirkazemi, Mohammad; Erfanianfar, Ghazaleh; Tanaka, Masayuki

    2016-05-01

    We study the distribution and evolution of the stellar mass and the star formation rate (SFR) of the brightest group galaxies (BGGs) over 0.04 < z < 1.3 using a large sample of 407 X-ray galaxy groups selected from the COSMOS, AEGIS, and XMM-LSS fields. We compare our results with predictions from the semi-analytic models based on the Millennium simulation. In contrast to model predictions, we find that, as the Universe evolves, the stellar mass distribution evolves towards a normal distribution. This distribution tends to skew to low-mass BGGs at all redshifts implying the presence of a star-forming population of the BGGs with MS ˜ 1010.5 M⊙ which results in the shape of the stellar mass distribution deviating from a normal distribution. In agreement with the models and previous studies, we find that the mean stellar mass of BGGs grows with time by a factor of ˜2 between z = 1.3 and z = 0.1, however, the significant growth occurs above z = 0.4. The BGGs are not entirely a dormant population of galaxies, as low-mass BGGs in low-mass haloes are more active in forming stars than the BGGs in more massive haloes, over the same redshift range. We find that the average SFR of the BGGs evolves steeply with redshift and fraction of the passive BGGs increases as a function of increasing stellar mass and halo mass. Finally, we show that the specific SFR of the BGGs within haloes with M200 ≤ 1013.4 M⊙ decreases with increasing halo mass at z < 0.4.

  5. On the reversal of star formation rate-density relation at z = 1: Insights from simulations

    SciTech Connect

    Tonnesen, Stephanie; Cen, Renyue E-mail: cen@astro.princeton.edu

    2014-06-20

    Recent surveys have found a reversal of the star formation rate (SFR)-density relation at z = 1 from that at z = 0, while the sign of the slope of the color-density relation remains unchanged. We use adaptive mesh refinement cosmological hydrodynamic simulations of a 21 × 24 × 20 h {sup –3} Mpc{sup 3} region to examine the SFR-density and color-density relations of galaxies at z = 0 and z = 1. The local environmental density is defined by the dark matter mass in spheres of radius 1 h {sup –1} Mpc, and we probe two decades of environmental densities. Our simulations produce a large increase of SFR with density at z = 1, as in the Elbaz et al. observations. We also find a significant evolution to z = 0, where the SFR-density relation is much flatter. The simulated color-density relation is consistent from z = 1 to z = 0, in agreement with observations. We find that the increase in SFR with local density at z = 1 is due to a growing population of star-forming galaxies in higher-density environments. At z = 0 and z = 1 both the SFR and cold gas mass are correlated with the galaxy halo mass, and therefore the correlation between median halo mass and local density is an important cause of the SFR-density relation at both redshifts. However, at z = 0 the local density on 1 h {sup –1} Mpc scales affects galaxy SFRs as much as halo mass. Finally, we find indications that while at z = 0 high-density environments depress galaxy SFRs, at z = 1 high-density environments tend to increase SFRs.

  6. Ozone-Induced Dissociation of Conjugated Lipids Reveals Significant Reaction Rate Enhancements and Characteristic Odd-Electron Product Ions

    NASA Astrophysics Data System (ADS)

    Pham, Huong T.; Maccarone, Alan T.; Campbell, J. Larry; Mitchell, Todd W.; Blanksby, Stephen J.

    2013-02-01

    Ozone-induced dissociation (OzID) is an alternative ion activation method that relies on the gas phase ion-molecule reaction between a mass-selected target ion and ozone in an ion trap mass spectrometer. Herein, we evaluated the performance of OzID for both the structural elucidation and selective detection of conjugated carbon-carbon double bond motifs within lipids. The relative reactivity trends for [M + X]+ ions (where X = Li, Na, K) formed via electrospray ionization (ESI) of conjugated versus nonconjugated fatty acid methyl esters (FAMEs) were examined using two different OzID-enabled linear ion-trap mass spectrometers. Compared with nonconjugated analogues, FAMEs derived from conjugated linoleic acids were found to react up to 200 times faster and to yield characteristic radical cations. The significantly enhanced reactivity of conjugated isomers means that OzID product ions can be observed without invoking a reaction delay in the experimental sequence (i.e., trapping of ions in the presence of ozone is not required). This possibility has been exploited to undertake neutral-loss scans on a triple quadrupole mass spectrometer targeting characteristic OzID transitions. Such analyses reveal the presence of conjugated double bonds in lipids extracted from selected foodstuffs. Finally, by benchmarking of the absolute ozone concentration inside the ion trap, second order rate constants for the gas phase reactions between unsaturated organic ions and ozone were obtained. These results demonstrate a significant influence of the adducting metal on reaction rate constants in the fashion Li > Na > K.

  7. Determination of the Rate of Formation of Hydroceramic Waste Forms made with INEEL Calcined Wastes

    SciTech Connect

    Barry Scheetz; Johnson Olanrewaju

    2001-10-15

    The formulation, synthesis, characterization and hydration kinetics of hydroceramic waste forms designed as potential hosts for existing INEEL calcine high-level wastes have been established as functions of temperature and processing time. Initial experimentations were conducted with several aluminosilicate pozzolanic materials, ranging from fly ash obtained from various power generating coal and other combustion industries to reactive alumina, natural clays and ground bottled glass powders. The final selection criteria were based on the ease of processing, excellent physical properties and chemical durability (low-leaching) determined from the PCT test produced in hydroceramic. The formulation contains vermiculite, Sr(NO32), CsC1, NaOH, thermally altered (calcined natural clay) and INEEL simulated calcine high-level nuclear wastes and 30 weight percent of fluorinel blend calcine and zirconia calcine. Syntheses were carried out at 75-200 degree C at autogeneous water pressure (100% relative humidity) at various time intervals. The resulting monolithic compact products were hard and resisted breaking when dropped from a 5 ft height. Hydroceramic host mixed with fluorinel blend calcine and processed at 75 degree C crumbled into rice hull-side grains or developed scaly flakes. However, the samples equally possessed the same chemical durability as their unbroken counterparts. Phase identification by XRD revealed that hydroceramic host crystallized type zeolite at 75-150 degree C and NaP1 at 175-200 degree C in addition to the presence of quartz phase originating from the clay reactant. Hydroceramic host mixed with either fluorinel blend calcine or zirconia calcine crystallized type A zeolite at 75-95 degree C, formed a mixture of type A zeolite and hydroxysodalite at 125-150 degree C and hydroxysodalite at 175-200 degree C. Quartz, calcium fluoride and zirconia phases from the clay reactant and the two calcine wastes were also detected. The PCT test solution

  8. Methane hydrate synthesis from ice: Influence of pressurization and ethanol on optimizing formation rates and hydrate yield

    USGS Publications Warehouse

    Chen, Po-Chun.; Huang, Wuu-Liang; Stern, Laura A.

    2010-01-01

    Polycrystalline methane gas hydrate (MGH) was synthesized using an ice-seeding method to investigate the influence of pressurization and ethanol on the hydrate formation rate and gas yield of the resulting samples. When the reactor is pressurized with CH4 gas without external heating, methane hydrate can be formed from ice grains with yields up to 25% under otherwise static conditions. The rapid temperature rise caused by pressurization partially melts the granular ice, which reacts with methane to form hydrate rinds around the ice grains. The heat generated by the exothermic reaction of methane hydrate formation buffers the sample temperature near the melting point of ice for enough time to allow for continuous hydrate growth at high rates. Surprisingly, faster rates and higher yields of methane hydrate were found in runs with lower initial temperatures, slower rates of pressurization, higher porosity of the granular ice samples, or mixtures with sediments. The addition of ethanol also dramatically enhanced the formation of polycrystalline MGH. This study demonstrates that polycrystalline MGH with varied physical properties suitable for different laboratory tests can be manufactured by controlling synthesis procedures or parameters. Subsequent dissociation experiments using a gas collection apparatus and flowmeter confirmed high methane saturation (CH 4·2O, with n = 5.82 ± 0.03) in the MGH. Dissociation rates of the various samples synthesized at diverse conditions may be fitted to different rate laws, including zero and first order.

  9. Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation

    USGS Publications Warehouse

    Reddy, Michael M.

    2012-01-01

    Increases in ocean surface water dissolved carbon dioxide (CO2) concentrations retard biocalcification by reducing calcite supersaturation (Ωc). Reduced calcification rates may influence growth-rate dependent magnesium ion (Mg) incorporation into biogenic calcite modifying the use of calcifying organisms as paleoclimate proxies. Fulvic acid (FA) at biocalcification sites may further reduce calcification rates. Calcite growth-rate inhibition by FA and Mg, two common constituents of seawater and soil water involved in the formation of biogenic calcite, was measured separately and in combination under identical, highly reproducible experimental conditions. Calcite growth rates (pH=8.5 and Ωc=4.5) are reduced by FA (0.5 mg/L) to 47% and by Mg (10−4 M) to 38%, compared to control experiments containing no added growth-rate inhibitor. Humic acid (HA) is twice as effective a calcite growth-rate inhibitor as FA. Calcite growth rate in the presence of both FA (0.5 mg/L) and Mg (10−4 M) is reduced to 5% of the control rate. Mg inhibits calcite growth rates by substitution for calcium ion at the growth site. In contrast, FA inhibits calcite growth rates by binding multiple carboxylate groups on the calcite surface. FA and Mg together have an increased affinity for the calcite growth sites reducing calcite growth rates.

  10. Use of Microfluidic Technology To Analyze Gene Expression during Staphylococcus aureus Biofilm Formation Reveals Distinct Physiological Niches

    PubMed Central

    Moormeier, Derek E.; Endres, Jennifer L.; Mann, Ethan E.; Sadykov, Marat R.; Horswill, Alexander R.; Rice, Kelly C.; Fey, Paul D.

    2013-01-01

    The Staphylococcus aureus cid and lrg operons play significant roles in the control of autolysis and accumulation of extracellular genomic DNA (eDNA) during biofilm development. Although the molecular mechanisms mediating this control are only beginning to be revealed, it is clear that cell death must be limited to a subfraction of the biofilm population. In the present study, we tested the hypothesis that cid and lrg expression varies during biofilm development as a function of changes in the availability of oxygen. To examine cid and lrg promoter activity during biofilm development, fluorescent reporter fusion strains were constructed and grown in a BioFlux microfluidic system, generating time-lapse epifluorescence images of biofilm formation, which allows the spatial and temporal localization of gene expression. Consistent with cid induction under hypoxic conditions, the cid::gfp fusion strain expressed green fluorescent protein predominantly within the interior of the tower structures, similar to the pattern of expression observed with a strain carrying a gfp fusion to the hypoxia-induced promoter controlling the expression of the lactose dehydrogenase gene. The lrg promoter was also expressed within towers but appeared more diffuse throughout the tower structures, indicating that it was oxygen independent. Unexpectedly, the results also demonstrated the existence of tower structures with different expression phenotypes and physical characteristics, suggesting that these towers exhibit different metabolic activities. Overall, the findings presented here support a model in which oxygen is important in the spatial and temporal control of cid expression within a biofilm and that tower structures formed during biofilm development exhibit metabolically distinct niches. PMID:23524683

  11. Pattern formation in the monocot embryo as revealed by NAM and CUC3 orthologues from Zea mays L.

    PubMed

    Zimmermann, Roman; Werr, Wolfgang

    2005-07-01

    All aerial parts of a higher plant originate from the shoot apical meristem (SAM), which is initiated during embryogenesis as a part of the basic body plan. In contrast to dicot species, the SAM in Zea mays is not established at an apico-central, but at a lateral position of the transition stage embryo. Genetic and molecular studies in dicots have revealed that members of the NAC gene family of plant-specific transcription factors such as NO APICAL MERISTEM (NAM) from Petunia or the CUP-SHAPED COTYLEDON (CUC) genes from Arabidopsis contribute essential functions to the establishment of the SAM and cotyledon separation. As an approach to the understanding of meristem formation in a monocot species, members of the maize NAC family highly related to the NAM/CUC genes were isolated and characterized. Our phylogenetic analysis indicates that two distinct NAM and CUC3 precursors already existed prior to the separation of mono- and dicot species. The allocation of the two maize paralogues, ZmNAM1 and ZmNAM2 together with PhNAM, AtCUC2 and AmCUP in one sub-branch and the corresponding expression patterns support their contribution to SAM establishment. In contrast, the ZmCUC3 orthologue is associated with boundary specification at the SAM periphery, where it visualizes which fraction of cells in the SAM is committed to a new leaf primordium. Other maize NAC gene family members are clearly positioned outside of this NAM/CUC3 branch and also exhibit highly cell type-specific expression patterns. PMID:16158242

  12. Star Formation Rates in Cooling Flow Clusters: A UV Pilot Study with Archival XMM-Newton Optical Monitor Data

    NASA Technical Reports Server (NTRS)

    Hicks, A. K.; Mushotzky, R.

    2006-01-01

    We have analyzed XMM-Newton Optical Monitor (OM) UV (180-400 nm) data for a sample of 33 galaxies. 30 are cluster member galaxies, and nine of these are central cluster galaxies (CCGs) in cooling flow clusters having mass deposition rates which span a range of 8 - 525 Solar Mass/yr. By comparing the ratio of UV to 2MASS J band fluxes, we find a significant UV excess in many, but not all, cooling flow CCGs, a finding consistent with the outcome of previous studies based on optical imaging data (McNamara & O'Connell 1989; Cardiel, Gorgas, & Aragon-Salamanca 1998; Crawford et al. 1999). This UV excess is a direct indication of the presence of young massive stars, and therefore recent star formation, in these galaxies. Using the Starburst99 spectral energy distribution (SED) model of continuous star formation over a 900 Myr period, we derive star formation rates of 0.2 - 219 solar Mass/yr for the cooling flow sample. For 2/3 of this sample it is possible to equate Chandra/XMM cooling flow mass deposition rates with UV inferred star formation rates, for a combination of starburst lifetime and IMF slope. This is a pilot study of the well populated XMM UV cluster archive and a more extensive follow up study is currently underway.

  13. Star Formation Rates in Cooling Flow Clusters: A UV Pilot Study with Archival XMM-Newton Optical Monitor Data

    NASA Technical Reports Server (NTRS)

    Hicks, A. K.; Mushotzky, R.

    2005-01-01

    We have analyzed XMM-Newton Optical Monitor (OM) UV (180-400 nm) data for a sample of 33 galaxies. 30 are cluster member galaxies, and nine of these are central cluster galaxies (CCGs) in cooling flow clusters having mass deposition rates which span a range of 8 - 525 solar mass per year. By comparing the ratio of UV to 2MASS J band fluxes, we find a significant UV excess in many, but not all, cooling flow CCGs, a finding consistent with the outcome of previous studies based on optical imaging data (McNamara & O Connell 1989; Cardiel, Gorgas, & Aragon-Salamanca 1998; Crawford et al. 1999). This UV excess is a direct indication of the presence of young massive stars, and therefore recent star formation, in these galaxies. Using the Starburst99 spectral energy distribution (SED) model of continuous star formation over a 900 Myr period, we derive star formation rates of 0.2 - 219 solar mass per year for the cooling flow sample. For 2/3 of this sample it is possible to equate Chandra/XMM cooling flow mass deposition rates with UV inferred star formation rates, for a combination of starburst lifetime and IMF slope. This is a pilot study of the well populated XMM UV cluster archive and a more extensive follow up study is currently underway.

  14. Multi-epoch very long baseline interferometric observations of the nuclear starburst region of NGC 253: Improved modeling of the supernova and star formation rates

    SciTech Connect

    Rampadarath, H.; Morgan, J. S.; Tingay, S. J.; Lenc, E.

    2014-01-01

    The results of multi-epoch observations of the southern starburst galaxy, NGC 253, with the Australian Long Baseline Array at 2.3 GHz are presented. As with previous radio interferometric observations of this galaxy, no new sources were discovered. By combining the results of this survey with Very Large Array observations at higher frequencies from the literature, spectra were derived and a free-free absorption model was fitted of 20 known sources in NGC 253. The results were found to be consistent with previous studies. The supernova remnant, 5.48-43.3, was imaged with the highest sensitivity and resolution to date, revealing a two-lobed morphology. Comparisons with previous observations of similar resolution give an upper limit of 10{sup 4} km s{sup –1} for the expansion speed of this remnant. We derive a supernova rate of <0.2 yr{sup –1} for the inner 300 pc using a model that improves on previous methods by incorporating an improved radio supernova peak luminosity distribution and by making use of multi-wavelength radio data spanning 21 yr. A star formation rate of SFR(M ≥ 5 M {sub ☉}) < 4.9 M {sub ☉} yr{sup –1} was also estimated using the standard relation between supernova and star formation rates. Our improved estimates of supernova and star formation rates are consistent with studies at other wavelengths. The results of our study point to the possible existence of a small population of undetected supernova remnants, suggesting a low rate of radio supernova production in NGC 253.

  15. Is There a Maximum Star Formation Rate in High-redshift Galaxies?

    NASA Astrophysics Data System (ADS)

    Barger, A. J.; Cowie, L. L.; Chen, C.-C.; Owen, F. N.; Wang, W.-H.; Casey, C. M.; Lee, N.; Sanders, D. B.; Williams, J. P.

    2014-03-01

    We use the James Clerk Maxwell Telescope's SCUBA-2 camera to image a 400 arcmin2 area surrounding the GOODS-N field. The 850 μm rms noise ranges from a value of 0.49 mJy in the central region to 3.5 mJy at the outside edge. From these data, we construct an 850 μm source catalog to 2 mJy containing 49 sources detected above the 4σ level. We use an ultradeep (11.5 μJy at 5σ) 1.4 GHz image obtained with the Karl G. Jansky Very Large Array together with observations made with the Submillimeter Array to identify counterparts to the submillimeter galaxies. For most cases of multiple radio counterparts, we can identify the correct counterpart from new and existing Submillimeter Array data. We have spectroscopic redshifts for 62% of the radio sources in the 9' radius highest sensitivity region (556/894) and 67% of the radio sources in the GOODS-N region (367/543). We supplement these with a modest number of additional photometric redshifts in the GOODS-N region (30). We measure millimetric redshifts from the radio to submillimeter flux ratios for the unidentified submillimeter sample, assuming an Arp 220 spectral energy distribution. We find a radio-flux-dependent K - z relation for the radio sources, which we use to estimate redshifts for the remaining radio sources. We determine the star formation rates (SFRs) of the submillimeter sources based on their radio powers and their submillimeter fluxes and find that they agree well. The radio data are deep enough to detect star-forming galaxies with SFRs >2000 M ⊙ yr-1 to z ~ 6. We find galaxies with SFRs up to ~6000 M ⊙ yr-1 over the redshift range z = 1.5-6, but we see evidence for a turn-down in the SFR distribution function above 2000 M ⊙ yr-1. The James Clerk Maxwell Telescope is operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the United Kingdom, the National Research Council of Canada, and (until 2013 March 31) the Netherlands Organisation for Scientific

  16. Is there a maximum star formation rate in high-redshift galaxies? , , ,

    SciTech Connect

    Barger, A. J.; Cowie, L. L.; Chen, C.-C.; Casey, C. M.; Lee, N.; Sanders, D. B.; Williams, J. P.; Owen, F. N.; Wang, W.-H.

    2014-03-20

    We use the James Clerk Maxwell Telescope's SCUBA-2 camera to image a 400 arcmin{sup 2} area surrounding the GOODS-N field. The 850 μm rms noise ranges from a value of 0.49 mJy in the central region to 3.5 mJy at the outside edge. From these data, we construct an 850 μm source catalog to 2 mJy containing 49 sources detected above the 4σ level. We use an ultradeep (11.5 μJy at 5σ) 1.4 GHz image obtained with the Karl G. Jansky Very Large Array together with observations made with the Submillimeter Array to identify counterparts to the submillimeter galaxies. For most cases of multiple radio counterparts, we can identify the correct counterpart from new and existing Submillimeter Array data. We have spectroscopic redshifts for 62% of the radio sources in the 9' radius highest sensitivity region (556/894) and 67% of the radio sources in the GOODS-N region (367/543). We supplement these with a modest number of additional photometric redshifts in the GOODS-N region (30). We measure millimetric redshifts from the radio to submillimeter flux ratios for the unidentified submillimeter sample, assuming an Arp 220 spectral energy distribution. We find a radio-flux-dependent K – z relation for the radio sources, which we use to estimate redshifts for the remaining radio sources. We determine the star formation rates (SFRs) of the submillimeter sources based on their radio powers and their submillimeter fluxes and find that they agree well. The radio data are deep enough to detect star-forming galaxies with SFRs >2000 M {sub ☉} yr{sup –1} to z ∼ 6. We find galaxies with SFRs up to ∼6000 M {sub ☉} yr{sup –1} over the redshift range z = 1.5-6, but we see evidence for a turn-down in the SFR distribution function above 2000 M {sub ☉} yr{sup –1}.

  17. Star formation rate and extinction in faint z ∼ 4 Lyman break galaxies

    SciTech Connect

    To, Chun-Hao; Wang, Wei-Hao; Owen, Frazer N.

    2014-09-10

    We present a statistical detection of 1.5 GHz radio continuum emission from a sample of faint z ∼ 4 Lyman break galaxies (LBGs). To constrain their extinction and intrinsic star formation rate (SFR), we combine the latest ultradeep Very Large Array 1.5 GHz radio image and the Hubble Space Telescope Advanced Camera for Surveys (ACS) optical images in the GOODS-N. We select a large sample of 1771 z ∼ 4 LBGs from the ACS catalog using B {sub F435W}-dropout color criteria. Our LBG samples have I {sub F775W} ∼ 25-28 (AB), ∼0-3 mag fainter than M{sub UV}{sup ⋆} at z ∼ 4. In our stacked radio images, we find the LBGs to be point-like under our 2'' angular resolution. We measure their mean 1.5 GHz flux by stacking the measurements on the individual objects. We achieve a statistical detection of S {sub 1.5} {sub GHz} = 0.210 ± 0.075 μJy at ∼3σ for the first time on such a faint LBG population at z ∼ 4. The measurement takes into account the effects of source size and blending of multiple objects. The detection is visually confirmed by stacking the radio images of the LBGs, and the uncertainty is quantified with Monte Carlo simulations on the radio image. The stacked radio flux corresponds to an obscured SFR of 16.0 ± 5.7 M {sub ☉} yr{sup –1}, and implies a rest-frame UV extinction correction factor of 3.8. This extinction correction is in excellent agreement with that derived from the observed UV continuum spectral slope, using the local calibration of Meurer et al. This result supports the use of the local calibration on high-redshift LBGs to derive the extinction correction and SFR, and also disfavors a steep reddening curve such as that of the Small Magellanic Cloud.

  18. Digestion of high rate activated sludge coupled to biochar formation for soil improvement in the tropics.

    PubMed

    Nansubuga, Irene; Banadda, Noble; Ronsse, Frederik; Verstraete, Willy; Rabaey, Korneel

    2015-09-15

    High rate activated sludge (HRAS) is well-biodegradable sludge enabling energy neutrality of wastewater treatment plants via anaerobic digestion. However, even through successful digestion a notable residue still remains. Here we investigated whether this residue can be converted to biochar, for its use as a fertilizer or as a solid fuel, and assessed its characteristics and overall process efficiency. In a first phase, HRAS was anaerobicaly digested under mesophilic conditions at a sludge retention time of 20 days. HRAS digested well (57.9 ± 6.2% VS degradation) producing on average 0.23 ± 0.04 L CH4 per gram VS fed. The digestate particulates were partially air-dried to mimic conditions used in developing countries, and subsequently converted to biochar by fixed-bed slow pyrolysis at a residence time of 15 min and at highest heating temperatures (HHT) of 300 °C, 400 °C and 600 °C. Subsequently, the produced chars were characterized by proximate analysis, CHN-elemental analysis, pH in solution and bomb calorimetry for higher heating value. The yield and volatile matter decreased with increasing HHT while ash content and fixed carbon increased with increasing HHT. The produced biochar showed properties optimal towards soil amendment when produced at a temperature of 600 °C with values of 5.91 wt%, 23.75 wt%, 70.35% on dry basis (db) and 0.44 for volatile matter, fixed carbon, ash content and H/C ratio, respectively. With regard to its use for energy purposes, the biochar represented a lower calorific value than the dried HRAS digestate likely due to high ash content. Based on these findings, it can be concluded that anaerobic digestion of HRAS and its subsequent biochar formation at HHT of 600 °C represents an attractive route for sludge management in tropic settings like in Uganda, coupling carbon capture to energy generation, carbon sequestration and nutrient recovery. PMID:26072019

  19. Narrow-band Imaging of Massive Star-Forming Regions: Tracing Outflows and the Rate of Star-Formation

    NASA Astrophysics Data System (ADS)

    Hall, Kendall; Willis, Sarah; Hora, Joseph L.

    2016-01-01

    Narrowband images targeting ionized hydrogen (Brackett gamma, 2.17 microns) and molecular hydrogen (2.12 microns) were obtained for six massive star-forming regions within the Milky Way, NGC 6334, G305, G3333, G3264, G3266, and G351. These regions are within 1-4 kpc from our solar system. The narrowband flux in Brackett gamma was used as a star-formation tracer to calculate a star-formation rate for each region. This is compared with other star-formation rates found using other methods such as the count of young stars and YSOs, and rates calculated from using other tracers (e.g. 70 micron monochromatic luminosity). The molecular hydrogen narrowband images were manually searched to locate outflows from young stars. Once these outflows are identified, it may help to get a better survey of the young stellar population. A better understanding of the stellar population distribution can lead to more accurate star-formation rates to compare to those calculated from star-formation tracers. We found the regions NGC 6334 and G3266 to have the highest levels of ongoing star formation activity as indicated by the number of molecular hydrogen objects (MHOs) detected. There are a total of 279 cataloged MHOs in 181 categorized systems for the six regions. There are a total of 150 identified potential driving sources.This work was supported in part by the NSF REU and DoD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution.

  20. Dissociation from the Oligomeric State Is the Rate-limiting Step in Fibril Formation by κ-Casein*

    PubMed Central

    Ecroyd, Heath; Koudelka, Tomas; Thorn, David C.; Williams, Danielle M.; Devlin, Glyn; Hoffmann, Peter; Carver, John A.

    2008-01-01

    Amyloid fibrils are aggregated and precipitated forms of protein in which the protein exists in highly ordered, long, unbranching threadlike formations that are stable and resistant to degradation by proteases. Fibril formation is an ordered process that typically involves the unfolding of a protein to partially folded states that subsequently interact and aggregate through a nucleation-dependent mechanism. Here we report on studies investigating the molecular basis of the inherent propensity of the milk protein, κ-casein, to form amyloid fibrils. Using reduced and carboxymethylated κ-casein (RCMκ-CN), we show that fibril formation is accompanied by a characteristic increase in thioflavin T fluorescence intensity, solution turbidity, and β-sheet content of the protein. However, the lag phase of RCMκ-CN fibril formation is independent of protein concentration, and the rate of fibril formation does not increase upon the addition of seeds (preformed fibrils). Therefore, its mechanism of fibril formation differs from the archetypal nucleation-dependent aggregation mechanism. By digestion with trypsin or proteinase K and identification by mass spectrometry, we have determined that the region from Tyr25 to Lys86 is incorporated into the core of the fibrils. We suggest that this region, which is predicted to be aggregation-prone, accounts for the amyloidogenic nature of κ-casein. Based on these data, we propose that fibril formation by RCMκ-CN occurs through a novel mechanism whereby the rate-limiting step is the dissociation of an amyloidogenic precursor from an oligomeric state rather than the formation of stable nuclei, as has been described for most other fibril-forming systems. PMID:18245081

  1. Dissociation from the oligomeric state is the rate-limiting step in fibril formation by kappa-casein.

    PubMed

    Ecroyd, Heath; Koudelka, Tomas; Thorn, David C; Williams, Danielle M; Devlin, Glyn; Hoffmann, Peter; Carver, John A

    2008-04-01

    Amyloid fibrils are aggregated and precipitated forms of protein in which the protein exists in highly ordered, long, unbranching threadlike formations that are stable and resistant to degradation by proteases. Fibril formation is an ordered process that typically involves the unfolding of a protein to partially folded states that subsequently interact and aggregate through a nucleation-dependent mechanism. Here we report on studies investigating the molecular basis of the inherent propensity of the milk protein, kappa-casein, to form amyloid fibrils. Using reduced and carboxymethylated kappa-casein (RCMkappa-CN), we show that fibril formation is accompanied by a characteristic increase in thioflavin T fluorescence intensity, solution turbidity, and beta-sheet content of the protein. However, the lag phase of RCMkappa-CN fibril formation is independent of protein concentration, and the rate of fibril formation does not increase upon the addition of seeds (preformed fibrils). Therefore, its mechanism of fibril formation differs from the archetypal nucleation-dependent aggregation mechanism. By digestion with trypsin or proteinase K and identification by mass spectrometry, we have determined that the region from Tyr(25) to Lys(86) is incorporated into the core of the fibrils. We suggest that this region, which is predicted to be aggregation-prone, accounts for the amyloidogenic nature of kappa-casein. Based on these data, we propose that fibril formation by RCMkappa-CN occurs through a novel mechanism whereby the rate-limiting step is the dissociation of an amyloidogenic precursor from an oligomeric state rather than the formation of stable nuclei, as has been described for most other fibril-forming systems. PMID:18245081

  2. Comparing FIR, UV and SED star formation rates for IR-luminous galaxies at 1≤z≤2 in CANDELS

    NASA Astrophysics Data System (ADS)

    Pforr, Janine; Dickinson, Mark; Kartaltepe, Jeyhan; Inami, Hanae; Penner, Kyle

    2015-08-01

    Galaxy formation and evolution studies rely on the robust determination of galaxy properties such as stellar masses and star formation rates (SFR). One the one hand these are important to distinguish between star bursting galaxies, normally star forming galaxies and those in the process of quenching and reveal the underlying processes causing these phenomena. On the other hand, they are crucial to derive reliable estimates of global properties like the star formation rate density of the Universe and the stellar mass assembly. We exploit the excellent multi-wavelength data in the GOODS-S, GOODS-N, UDS and COSMOS CANDELS fields ranging from deep ground and space-based optical data, deep-NIR HST data from CANDELS to the deepest FIR PACS data available from CANDELS-Herschel and Pep/GOODS-Herschel to estimate SFRs of IR-luminous galaxies between redshift 1 and 2. We determine SFRs in three different ways:1) from SED-fitting to the optical/IR multi-wavelength data, 2) from far-IR luminosities using 24 micron and Herschel PACS fluxes and 3) from UV slope and UV luminosity measurements. While for the majority of objects the different estimates agree very well, we find a subsample of outliers that are classified as pseudo-quiescent by the SED-fit. We present possible reasons for these misclassifications as well as potential remedies.

  3. Thermochemical pretreatment of lignocellulose to enhance methane fermentation. I. Monosaccharide and furfurals hydrothermal decomposition and product formation rates

    SciTech Connect

    Baugh, K.D.; McCarty, P.L.

    1988-01-01

    Over a pH range 1-4 and temperatures from 170 to 230/sup 0/C, the decomposition rates of xylose, galactose, mannose, glucose, 2-furfural, and 5-hydroxymethyl-2-furfural (5-HMF) were pseudo first order. The effect of temperature and pH on the pseudo first-order decomposition rate constants was modeled using the Arrhenius equation and acid-base catalysis, respectively. Decomposition rates of the monosaccharides were minimum at a pH 2-2.5. Above pH 2.5, the monosaccharide decomposition was base catalyzed, with acid catalysis occurring at a pH of less than 2 for glucose. The furfurals were subject to acid catalysis at below ca. pH 3.5. The hydrothermal conversion of glucose to its decomposition products during thermochemical pretreatment can be modeled as a combination of series and parallel reactions. The formation rates of identified soluble products from glucose decomposition, 5-HMF and levulinic acid, were also functions of temperature and pH. The rate of 5-HMF formation relative to glucose decomposition decreased as the pH increased from 2.0 to 4.0, with levulinic acid formation only detected when the pH was 2.5 or less. For glucose decomposition, humic solids accounted for ca. 20% of the decomposition products.

  4. Estimation of the ozone formation rate in the atmospheric boundary layer over a background region of Western Siberia

    NASA Astrophysics Data System (ADS)

    Antokhin, P. N.; Antokhina, O. Y.; Belan, B. D.

    2015-11-01

    The ozone formation rate in the atmospheric boundary layer (ABL) and the ozone inflow from the free atmosphere have been studied experimentally. The obtained estimates are based on the data of airborne sounding carried out over a background region of Western Siberia. As a result, it is obtained that the rate of ozone inflow from the upper atmospheric layers is only 20% of the rate of photochemical formation of ozone inside ABL. The vertical profiles of ozone flows in ABL have been additionally calculated based on the k-theory with the approach proposed by Troen and Mahrt. It has been shown in the calculations that the maximum of the ozone concentration in ABL is formed due to photochemical reactions from precursor gases.

  5. Herschel reveals the obscured star formation in HiZELS Hα emitters at z = 1.47

    NASA Astrophysics Data System (ADS)

    Ibar, E.; Sobral, D.; Best, P. N.; Ivison, R. J.; Smail, I.; Arumugam, V.; Berta, S.; Béthermin, M.; Bock, J.; Cava, A.; Conley, A.; Farrah, D.; Geach, J.; Ikarashi, S.; Kohno, K.; Le Floc'h, E.; Lutz, D.; Magdis, G.; Magnelli, B.; Marsden, G.; Oliver, S. J.; Page, M. J.; Pozzi, F.; Riguccini, L.; Schulz, B.; Seymour, N.; Smith, A. J.; Symeonidis, M.; Wang, L.; Wardlow, J.; Zemcov, M.

    2013-10-01

    We describe the far-infrared (far-IR; rest-frame 8-1000-μm) properties of a sample of 443 Hα-selected star-forming galaxies in the Cosmic Evolution Survey (COSMOS) and Ultra Deep Survey (UDS) fields detected by the High-redshift Emission Line Survey (HiZELS) imaging survey. Sources are identified using narrow-band filters in combination with broad-band photometry to uniformly select Hα (and [O II] if available) emitters in a narrow redshift slice at z = 1.47 ± 0.02. We use a stacking approach in Spitzer-MIPS mid-IR, Herschel-PACS/SPIRE far-IR [from the PACS Evolutionary Prove (PEP) and Herschel Multi-tiered Extragalactic Survey (HerMES)] and AzTEC mm-wave images to describe their typical far-IR properties. We find that HiZELS galaxies with observed Hα luminosities of L(Hα)obs ≈ 108.1-9.1 L⊙ ( ≈ 1041.7-42.7 erg s-1) have bolometric far-IR luminosities of typical luminous IR galaxies, L(8-1000 μ m)≈ 10^{11.41^{+0.04}_{-0.06}} L⊙. Combining the Hα and far-IR luminosities, we derive median star formation rates (SFRs) of SFRHα, FIR = 32 ± 5 M⊙ yr-1 and Hα extinctions of AHα = 1.0 ± 0.2 mag. Perhaps surprisingly, little difference is seen in typical HiZELS extinction levels compared to local star-forming galaxies. We confirm previous empirical stellar mass (M*) to AHα relations and the little or no evolution up to z = 1.47. For HiZELS galaxies (or similar samples) we provide an empirical parametrization of the SFR as a function of rest-frame (u - z) colours and 3.6-μm photometry - a useful proxy to aid in the absence of far-IR detections in high-z galaxies. We find that the observed Hα luminosity is a dominant SFR tracer when rest-frame (u - z) colours are ≲0.9 mag or when Spitzer-3.6-μm photometry is fainter than 22 mag (Vega) or when stellar masses are lower than 109.7 M⊙. We do not find any correlation between the [O II]/Hα and far-IR luminosity, suggesting that this emission line ratio does not trace the extinction of the most

  6. Genome-wide mutagenesis of Xanthomonas axonopodis pv. citri reveals novel genetic determinants and regulation mechanisms of biofilm formation.

    PubMed

    Li, Jinyun; Wang, Nian

    2011-01-01

    Xanthomonas axonopodis pv. citri (Xac) causes citrus canker disease, a major threat to citrus production worldwide. Accumulating evidence suggests that the formation of biofilms on citrus leaves plays an important role in the epiphytic survival of this pathogen prior to the development of canker disease. However, the process of Xac biofilm formation is poorly understood. Here, we report a genome-scale study of Xac biofilm formation in which we identified 92 genes, including 33 novel genes involved in biofilm formation and 7 previously characterized genes, colR, fhaB, fliC, galU, gumD, wxacO, and rbfC, known to be important for Xac biofilm formation. In addition, 52 other genes with defined or putative functions in biofilm formation were identified, even though they had not previously reported been to be associated with biofilm formation. The 92 genes were isolated from 292 biofilm-defective mutants following a screen of a transposon insertion library containing 22,000 Xac strain 306 mutants. Further analyses indicated that 16 of the novel genes are involved in the production of extracellular polysaccharide (EPS) and/or lipopolysaccharide (LPS), 7 genes are involved in signaling and regulatory pathways, and 5 genes have unknown roles in biofilm formation. Furthermore, two novel genes, XAC0482, encoding a haloacid dehalogenase-like phosphatase, and XAC0494 (designated as rbfS), encoding a two-component sensor protein, were confirmed to be biofilm-related genes through complementation assays. Our data demonstrate that the formation of mature biofilm requires EPS, LPS, both flagellum-dependent and flagellum-independent cell motility, secreted proteins and extracellular DNA. Additionally, multiple signaling pathways are involved in Xac biofilm formation. This work is the first report on a genome-wide scale of the genetic processes of biofilm formation in plant pathogenic bacteria. The report provides significant new information about the genetic determinants and

  7. On the Inconsistency between Cosmic Stellar Mass Density and Star Formation Rate up to z ∼ 8

    NASA Astrophysics Data System (ADS)

    Yu, H.; Wang, F. Y.

    2016-04-01

    In this paper, we test the discrepancy between the stellar mass density (SMD) and instantaneous star formation rate in the redshift range 0 < z < 8 using a large observational data sample. We first compile the measurements of SMDs up to z ∼ 8. Comparing the observed SMDs with the time-integral of instantaneous star formation history (SFH), we find that the observed SMDs are lower than that implied from the SFH at z < 4. We also use the Markov chain Monte Carlo (MCMC) method to derive the best-fitting SFH from the observed SMD data. At 0.5 < z < 6, the observed star formation rate densities are larger than the best-fitting one, especially at z ∼ 2 where they are larger by a factor of about two. However, at lower (z < 0.5) and higher redshifts (z > 6), the derived SFH is consistent with the observations. This is the first time that the discrepancy between the observed SMD and instantaneous star formation rate has been tested up to very high redshift z ≈ 8 using the MCMC method and a varying recycling factor. Several possible reasons for this discrepancy are discussed, such as underestimation of SMD, initial mass function, and evolution of cosmic metallicity.

  8. Steadily increasing star formation rates in galaxies observed at 3 ≲ z ≲ 5 in the CANDELS/GOODS-S field

    SciTech Connect

    Lee, Seong-Kook; Ferguson, Henry C.; Dahlen, Tomas; Somerville, Rachel S.; Giavalisco, Mauro; Wiklind, Tommy

    2014-03-10

    We investigate the star formation histories (SFHs) of high redshift (3 ≲ z ≲ 5) star-forming galaxies selected based on their rest-frame ultraviolet (UV) colors in the CANDELS/GOODS-S field. By comparing the results from the spectral-energy-distribution-fitting analysis with two different assumptions about the SFHs—i.e., exponentially declining SFHs as well as increasing ones, we conclude that the SFHs of high-redshift star-forming galaxies increase with time rather than exponentially decline. We also examine the correlations between the star formation rates (SFRs) and the stellar masses. When the galaxies are fit with rising SFRs, we find that the trend seen in the data qualitatively matches the expectations from a semi-analytic model of galaxy formation. The mean specific SFR is shown to increase with redshift, also in agreement with the theoretical prediction. From the derived tight correlation between stellar masses and SFRs, we derive the mean SFH of star-forming galaxies in the redshift range of 3 ≤ z ≤ 5, which shows a steep power-law (with power α = 5.85) increase with time. We also investigate the formation timescales and mean stellar population ages of these star-forming galaxies. Our analysis reveals that UV-selected star-forming galaxies have a broad range of the formation redshift. The derived stellar masses and the stellar population ages show positive correlation in a sense that more massive galaxies are on average older, but with significant scatter. This large scatter implies that the galaxies' mass is not the only factor which affects the growth or star formation of high-redshift galaxies.

  9. STAR FORMATION RATES FOR STARBURST GALAXIES FROM ULTRAVIOLET, INFRARED, AND RADIO LUMINOSITIES

    SciTech Connect

    Sargsyan, Lusine A.; Weedman, Daniel W. E-mail: dweedman@isc.astro.cornell.edu

    2009-08-20

    We present a comparison of star formation rates (SFR) determined from mid-infrared 7.7 {mu}m polycyclic aromatic hydrocarbon (PAH) luminosity [SFR(PAH)], from 1.4 GHz radio luminosity [SFR(radio)], and from far-ultraviolet luminosity [SFR(UV)] for a sample of 287 starburst galaxies with z < 0.5 having Spitzer IRS observations. The previously adopted relation log [SFR(PAH)] = log [{nu}L {sub {nu}}(7.7 {mu}m)] - 42.57 {+-} 0.2, for SFR in M{sub sun} yr{sup -1} and {nu}L {sub {nu}}(7.7 {mu}m) the luminosity at the peak of the 7.7 {mu}m PAH feature in erg s{sup -1}, is found to agree with SFR(radio). Comparing with SFR(UV) determined independently from ultraviolet observations of the same sources with the Galaxy Evolution Explorer mission (not corrected for dust extinction), the median log [SFR(PAH)/SFR(UV)] = 1.67, indicating that only 2% of the ultraviolet continuum typically escapes extinction by dust within a starburst. This ratio SFR(PAH)/SFR(UV) depends on infrared luminosity, with the form log [SFR(PAH)/SFR(UV)] = (0.53 {+-} 0.05)log [{nu}L{sub {nu}}(7.7 {mu}m)] - 21.5 {+-} 0.18, indicating that more luminous starbursts are also dustier. Using our adopted relation between {nu}L{sub {nu}}(7.7 {mu}m) and L {sub ir}, this becomes log [SFR(PAH)/SFR(UV)]= (0.53 {+-} 0.05)log L{sub ir} - 4.11 {+-} 0.18, for L{sub ir} in L{sub sun}. Only blue compact dwarf galaxies show comparable or greater SFR(UV) compared to SFR(PAH). We also find that the ratio SFR(PAH)/SFR(UV) is similar to that in infrared-selected starbursts for a sample of Markarian starburst galaxies originally selected using optical classification, which implies that there is no significant selection effect in SFR(PAH)/SFR(UV) using starburst galaxies discovered by Spitzer. These results indicate that SFRs determined with ultraviolet luminosities require dust corrections by a factor of {approx}10 for typical local starbursts but this factor increases to >700 for the most luminous starbursts at z {approx} 2

  10. Formation rates of complex organics in UV irradiated CH_3OH-rich ices. I. Experiments

    NASA Astrophysics Data System (ADS)

    Öberg, K. I.; Garrod, R. T.; van Dishoeck, E. F.; Linnartz, H.

    2009-09-01

    Context: Gas-phase complex organic molecules are commonly detected in the warm inner regions of protostellar envelopes, so-called hot cores. Recent models show that photochemistry in ices followed by desorption may explain the observed abundances. There is, however, a general lack of quantitative data on UV-induced complex chemistry in ices. Aims: This study aims to experimentally quantify the UV-induced production rates of complex organics in CH3OH-rich ices under a variety of astrophysically relevant conditions. Methods: The ices are irradiated with a broad-band UV hydrogen microwave-discharge lamp under ultra-high vacuum conditions, at 20-70 K, and then heated to 200 K. The reaction products are identified by reflection-absorption infrared spectroscopy (RAIRS) and temperature programmed desorption (TPD), through comparison with RAIRS and TPD curves of pure complex species, and through the observed effects of isotopic substitution and enhancement of specific functional groups, such as CH3, in the ice. Results: Complex organics are readily formed in all experiments, both during irradiation and during the slow warm-up of the ices after the UV lamp is turned off. The relative abundances of photoproducts depend on the UV fluence, the ice temperature, and whether pure CH3OH ice or CH3OH:CH4/CO ice mixtures are used. C2H6, CH3CHO, CH3CH2OH, CH3OCH3, HCOOCH3, HOCH2CHO and (CH2OH)2 are all detected in at least one experiment. Varying the ice thickness and the UV flux does not affect the chemistry. The derived product-formation yields and their dependences on different experimental parameters, such as the initial ice composition, are used to estimate the CH3OH photodissociation branching ratios in ice and the relative diffusion barriers of the formed radicals. At 20 K, the pure CH3OH photodesorption yield is 2.1(±1.0)×10-3 per incident UV photon, the photo-destruction cross section 2.6(±0.9)×10-18 cm^2. Conclusions: Photochemistry in CH3OH ices is efficient enough to

  11. Numerical Study of the Role of Magnetic Field Ramping Rate on the Structure Formation in Magnetorheological Fluids

    NASA Astrophysics Data System (ADS)

    Mohebi, M.; Jamasbi, N.; Flores, G. A.; Liu, Jing

    A molecular dynamics model is presented to understand the structural formation of MR fluids by including the thermal motion of the particles. The simulation results indicate that the complexity of the lateral pattern as viewed in the direction of the applied field increases with the rate of the application of external magnetic field. We have also found that the maximum range for attractive interaction (escape distance) for two initially straight chains increases with temperature. These results are relevant to understand the mechanisms and conditions for the formation of labyrinthine and columnar patterns found in MR fluids.

  12. Development of a Brief Rating Scale for the Formative Assessment of Positive Behaviors

    ERIC Educational Resources Information Center

    Cressey, James M.

    2010-01-01

    In order to provide effective social, emotional, and behavioral supports to all students, there is a need for formative assessment tools that can help determine the responsiveness of students to intervention. Schoolwide positive behavior support (SWPBS) is one framework that can provide evidence-based intervention within a 3-tiered model to reach…

  13. Another short-burst host galaxy with an optically obscured high star formation rate: The case of GRB 071227

    SciTech Connect

    Nicuesa Guelbenzu, A.; Klose, S.; Kann, D. A.; Rossi, A.; Schmidl, S.; Michałowski, M. J.; McKenzie, M. R. G.; Savaglio, S.; Greiner, J.; Hunt, L. K.; Gorosabel, J.

    2014-07-01

    We report on radio continuum observations of the host galaxy of the short gamma-ray burst 071227 (z = 0.381) with the Australia Telescope Compact Array. We detect the galaxy in the 5.5 GHz band with an integrated flux density of F {sub ν} = 43 ± 11 μJy, corresponding to an unobscured star-formation rate of about 24 M {sub ☉} yr{sup –1}, 40 times higher than what was found from optical emission lines. Among the ∼30 well-identified and studied host galaxies of short bursts this is the third case where the host is found to undergo an episode of intense star formation. This suggests that a fraction of all short-burst progenitors hosted in star-forming galaxies could be physically related to recent star formation activity, implying a relatively short merger timescale.

  14. The Relation between Star-Formation Rate and Stellar Mass of Galaxies at z ~ 1-4

    NASA Astrophysics Data System (ADS)

    Katsianis, A.; Tescari, E.; Wyithe, J. S. B.

    2016-07-01

    The relation between the star-formation Rate and stellar mass (M ⋆) of galaxies represents a fundamental constraint on galaxy formation, and has been studied extensively both in observations and cosmological hydrodynamic simulations. However, the observed amplitude of the star-formation rate-stellar mass relation has not been successfully reproduced in simulations, indicating either that the halo accretion history and baryonic physics are poorly understood/modelled or that observations contain biases. In this paper, we examine the evolution of the SFR - M ⋆ relation of z ~ 1-4 galaxies and display the inconsistency between observed relations that are obtained using different techniques. We employ cosmological hydrodynamic simulations from various groups which are tuned to reproduce a range of observables and compare these with a range of observed SFR - M ⋆ relations. We find that numerical results are consistent with observations that use Spectral Energy Distribution techniques to estimate star-formation rates, dust corrections, and stellar masses. On the contrary, simulations are not able to reproduce results that were obtained by combining only UV and IR luminosities (UV+IR). These imply star-formation rates at a fixed stellar mass that are larger almost by a factor of 5 than those of Spectral Energy Distribution measurements for z ~ 1.5-4. For z < 1.5, the results from simulations, Spectral Energy Distribution fitting techniques and IR+UV conversion agree well. We find that surveys that preferably select star-forming galaxies (e.g. by adopting Lyman-break or blue selection) typically predict a larger median/average star-formation rate at a fixed stellar mass especially for high mass objects, with respect to mass selected samples and hydrodynamic simulations. Furthermore, we find remarkable agreement between the numerical results from various authors who have employed different cosmological codes and run simulations with different resolutions. This is

  15. Research perspectives and role of lactose uptake rate revealed by its study using 14C-labelled lactose in whey fermentation.

    PubMed

    Golfinopoulos, Aristidis; Kopsahelis, Nikolaos; Tsaousi, Konstantina; Koutinas, Athanasios A; Soupioni, Magdalini

    2011-03-01

    The present investigation examines the effect of pH, temperature and cell concentration on lactose uptake rate, in relation with kinetics of whey fermentation using kefir and determines the optimum conditions of these parameters. Lactose uptake rate was measured by adding (14)C-labelled lactose in whey. The results reveal the role of lactose uptake rate, being the main factor that affects the rate of fermentation, in contrast to the activity of the enzymes involved in lactose bioconversion process. Lactose uptake rate results discussion showed that mainly Ca(2+) is responsible for the reduced whey fermentation rate in comparison with fermentations using synthetic media containing lactose. Likewise, the results draw up perspectives on whey fermentation research to improve whey fermentation rate. Those perspectives are research to remove Ca(2+) from whey, the use of nano and microtubular biopolymers and promoters such as γ-alumina pellets and volcan foaming rock kissiris in order to accelerate whey fermentation. PMID:21232943

  16. Stellar Masses and Start Formation Rates of Lensed Dusty Star-Forming Galaxies from the SPT Survey

    NASA Astrophysics Data System (ADS)

    Ma, Jingzhe; Gonzalez, Anthony; SPT SMG Collaboration

    2016-01-01

    To understand cosmic mass assembly in the Universe at early epochs, we primarily rely on measurements of stellar mass and star formation rate of distant galaxies. In this paper, we present stellar masses and star formation rates of six high-redshift (2.8 ≤ z ≤ 5.7) dusty, star-forming galaxies (DSFGs) that are strongly gravitationally lensed by foreground galaxies. These sources were first discovered by the South Pole Telescope (SPT) at millimeter wavelengths and all have spectroscopic redshifts and robust lens models derived from ALMA observations. We have conducted follow-up observations, obtaining multi-wavelength imaging data, using HST, Spitzer, Herschel and the Atacama Pathfinder EXperiment (APEX). We use the high-resolution HST/WFC3 images to disentangle the background source from the foreground lens in Spitzer/IRAC data. The detections and upper limits provide important constraints on the spectral energy distributions (SEDs) for these DSFGs, yielding stellar masses, IR luminosities, and star formation rates (SFRs). The SED fits of six SPT sources show that the intrinsic stellar masses span a range more than one order of magnitude with a median value ˜ 5 ×1010M⊙. The intrinsic IR luminosities range from 4×1012L⊙ to 4×1013L⊙. They all have prodigious intrinsic star formation rates of 510 to 4800 M⊙yr-1. Compared to the star-forming main sequence (MS), these six DSFGs have specific SFRs that all lie above the MS, including two galaxies that are a factor of 10 higher than the MS. Our results suggest that we are witnessing the ongoing strong starburst events which may be driven by major mergers.

  17. Estimating the carbon sequestration capacity of shale formations using methane production rates.

    PubMed

    Tao, Zhiyuan; Clarens, Andres

    2013-10-01

    Hydraulically fractured shale formations are being developed widely for oil and gas production. They could also represent an attractive repository for permanent geologic carbon sequestration. Shales have a low permeability, but they can adsorb an appreciable amount of CO2 on fracture surfaces. Here, a computational method is proposed for estimating the CO2 sequestration capacity of a fractured shale formation and it is applied to the Marcellus shale in the eastern United States. The model is based on historical and projected CH4 production along with published data and models for CH4/CO2 sorption equilibria and kinetics. The results suggest that the Marcellus shale alone could store between 10.4 and 18.4 Gt of CO2 between now and 2030, which represents more than 50% of total U.S. CO2 emissions from stationary sources over the same period. Other shale formations with comparable pressure-temperature conditions, such as Haynesville and Barnett, could provide significant additional storage capacity. The mass transfer kinetic results indicate that injection of CO2 would proceed several times faster than production of CH4. Additional considerations not included in this model could either reinforce (e.g., leveraging of existing extraction and monitoring infrastructure) or undermine (e.g., leakage or seismicity potential) this approach, but the sequestration capacity estimated here supports continued exploration into this pathway for producing carbon neutral energy. PMID:23988277

  18. Critical rate of electrolyte circulation for preventing zinc dendrite formation in a zinc-bromine redox flow battery

    NASA Astrophysics Data System (ADS)

    Yang, Hyeon Sun; Park, Jong Ho; Ra, Ho Won; Jin, Chang-Soo; Yang, Jung Hoon

    2016-09-01

    In a zinc-bromine redox flow battery, a nonaqueous and dense polybromide phase formed because of bromide oxidation in the positive electrolyte during charging. This formation led to complicated two-phase flow on the electrode surface. The polybromide and aqueous phases led to different kinetics of the Br/Br- redox reaction; poor mixing of the two phases caused uneven redox kinetics on the electrode surface. As the Br/Br- redox reaction was coupled with the zinc deposition reaction, the uneven redox reaction on the positive electrode was accompanied by nonuniform zinc deposition and zinc dendrite formation, which degraded battery stability. A single-flow cell was operated at varying electrolyte circulation rates and current densities. Zinc dendrite formation was observed after cell disassembly following charge-discharge testing. In addition, the flow behavior in the positive compartment was observed by using a transparent version of the cell. At low rate of electrolyte circulation, the polybromide phase clearly separated from the aqueous phase and accumulated at the bottom of the flow frame. In the corresponding area on the negative electrode, a large amount of zinc dendrites was observed after charge-discharge testing. Therefore, a minimum circulation rate should be considered to avoid poor mixing of the positive electrolyte.

  19. Whole genome sequencing of Mycobacterium tuberculosis reveals slow growth and low mutation rates during latent infections in humans.

    PubMed

    Colangeli, Roberto; Arcus, Vic L; Cursons, Ray T; Ruthe, Ali; Karalus, Noel; Coley, Kathy; Manning, Shannon D; Kim, Soyeon; Marchiano, Emily; Alland, David

    2014-01-01

    Very little is known about the growth and mutation rates of Mycobacterium tuberculosis during latent infection in humans. However, studies in rhesus macaques have suggested that latent infections have mutation rates that are higher than that observed during active tuberculosis disease. Elevated mutation rates are presumed risk factors for the development of drug resistance. Therefore, the investigation of mutation rates during human latency is of high importance. We performed whole genome mutation analysis of M. tuberculosis isolates from a multi-decade tuberculosis outbreak of the New Zealand Rangipo strain. We used epidemiological and phylogenetic analysis to identify four cases of tuberculosis acquired from the same index case. Two of the tuberculosis cases occurred within two years of exposure and were classified as recently transmitted tuberculosis. Two other cases occurred more than 20 years after exposure and were classified as reactivation of latent M. tuberculosis infections. Mutation rates were compared between the two recently transmitted pairs versus the two latent pairs. Mean mutation rates assuming 20 hour generation times were 5.5 X 10(-10) mutations/bp/generation for recently transmitted tuberculosis and 7.3 X 10(-11) mutations/bp/generation for latent tuberculosis. Generation time versus mutation rate curves were also significantly higher for recently transmitted tuberculosis across all replication rates (p = 0.006). Assuming identical replication and mutation rates among all isolates in the final two years before disease reactivation, the u 20 hr mutation rate attributable to the remaining latent period was 1.6 × 10(-11) mutations/bp/generation, or approximately 30 fold less than that calculated during the two years immediately before disease. Mutations attributable to oxidative stress as might be caused by bacterial exposure to the host immune system were not increased in latent infections. In conclusion, we did not find any evidence to suggest

  20. Whole Genome Sequencing of Mycobacterium tuberculosis Reveals Slow Growth and Low Mutation Rates during Latent Infections in Humans

    PubMed Central

    Colangeli, Roberto; Arcus, Vic L.; Cursons, Ray T.; Ruthe, Ali; Karalus, Noel; Coley, Kathy; Manning, Shannon D.; Kim, Soyeon; Marchiano, Emily; Alland, David

    2014-01-01

    Very little is known about the growth and mutation rates of Mycobacterium tuberculosis during latent infection in humans. However, studies in rhesus macaques have suggested that latent infections have mutation rates that are higher than that observed during active tuberculosis disease. Elevated mutation rates are presumed risk factors for the development of drug resistance. Therefore, the investigation of mutation rates during human latency is of high importance. We performed whole genome mutation analysis of M. tuberculosis isolates from a multi-decade tuberculosis outbreak of the New Zealand Rangipo strain. We used epidemiological and phylogenetic analysis to identify four cases of tuberculosis acquired from the same index case. Two of the tuberculosis cases occurred within two years of exposure and were classified as recently transmitted tuberculosis. Two other cases occurred more than 20 years after exposure and were classified as reactivation of latent M. tuberculosis infections. Mutation rates were compared between the two recently transmitted pairs versus the two latent pairs. Mean mutation rates assuming 20 hour generation times were 5.5X10−10 mutations/bp/generation for recently transmitted tuberculosis and 7.3X10−11 mutations/bp/generation for latent tuberculosis. Generation time versus mutation rate curves were also significantly higher for recently transmitted tuberculosis across all replication rates (p = 0.006). Assuming identical replication and mutation rates among all isolates in the final two years before disease reactivation, the u20hr mutation rate attributable to the remaining latent period was 1.6×10−11 mutations/bp/generation, or approximately 30 fold less than that calculated during the two years immediately before disease. Mutations attributable to oxidative stress as might be caused by bacterial exposure to the host immune system were not increased in latent infections. In conclusion, we did not find any evidence to suggest

  1. Bluff formation and long-term recession rates, southwestern Lake Michigan

    SciTech Connect

    Rovey, C.W. II )

    1992-01-01

    Where eroding cohesive sediments are present, Lake Michigan bluffs range up to 140 ft. in height and expose multiple stratigraphic units. According to the model presented here, bluffs form as a wave cut terrace erodes inland from a point near the original shoreline. The erosion plane is nearly horizontal, in contrast with the eastward dip of the glacial units inherited from underlying bedrock. Therefore, terraces eroding inland (west) produce progressively higher bluffs and expose successively older units at the toe and beneath the lake. This process repeated several times as lake levels sequentially dropped to their modern stage. The initial modern shoreline, and hence the width of the wave cut terrace, was determined from 4 offshore seismic profiles. It is picked as an inflection point in the slope of the lake bed, occurring offshore of dipping reflectors intersecting the lake bottom. The calculated average recession rate over the 2,500 year duration of the modern stage is 5 ft/yr in contrast to average rates of 2 ft/yr measured over the last century. Thus rates decrease through time as the terrace widens and wave energy is damped. By correlating bluff height to amount of recession of modern bluffs, a third rate of 12 ft/yr of the first 800 years of a recession is calculated for relict bluffs formed at the Nipissing II level. The 3 rates define a steeply decaying exponential curve in early stages of bluff retreat, flattening into a nearly linear function after 1,000 years.

  2. The VMC survey - XIV. First results on the look-back time star formation rate tomography of the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Rubele, Stefano; Girardi, Léo; Kerber, Leandro; Cioni, Maria-Rosa L.; Piatti, Andrés E.; Zaggia, Simone; Bekki, Kenji; Bressan, Alessandro; Clementini, Gisella; de Grijs, Richard; Emerson, Jim P.; Groenewegen, Martin A. T.; Ivanov, Valentin D.; Marconi, Marcella; Marigo, Paola; Moretti, Maria-Ida; Ripepi, Vincenzo; Subramanian, Smitha; Tatton, Benjamin L.; van Loon, Jacco Th.

    2015-05-01

    We analyse deep images from the VISTA survey of the Magellanic Clouds in the YJ{K_s} filters, covering 14 deg2 (10 tiles), split into 120 subregions, and comprising the main body and Wing of the Small Magellanic Cloud (SMC). We apply a colour-magnitude diagram reconstruction method that returns their best-fitting star formation rate SFR(t), age-metallicity relation (AMR), distance and mean reddening, together with 68 per cent confidence intervals. The distance data can be approximated by a plane tilted in the East-West direction with a mean inclination of 39°, although deviations of up to ±3 kpc suggest a distorted and warped disc. After assigning to every observed star a probability of belonging to a given age-metallicity interval, we build high-resolution population maps. These dramatically reveal the flocculent nature of the young star-forming regions and the nearly smooth features traced by older stellar generations. They document the formation of the SMC Wing at ages <0.2 Gyr and the peak of star formation in the SMC Bar at ˜40 Myr. We clearly detect periods of enhanced star formation at 1.5 and 5 Gyr. The former is possibly related to a new feature found in the AMR, which suggests ingestion of metal-poor gas at ages slightly larger than 1 Gyr. The latter constitutes a major period of stellar mass formation. We confirm that the SFR(t) was moderately low at even older ages.

  3. GAMMA-RAY BURST HOST GALAXY SURVEYS AT REDSHIFT z {approx}> 4: PROBES OF STAR FORMATION RATE AND COSMIC REIONIZATION

    SciTech Connect

    Trenti, Michele; Perna, Rosalba; Levesque, Emily M.; Shull, J. Michael; Stocke, John T.

    2012-04-20

    Measuring the star formation rate (SFR) at high redshift is crucial for understanding cosmic reionization and galaxy formation. Two common complementary approaches are Lyman break galaxy (LBG) surveys for large samples and gamma-ray burst (GRB) observations for sensitivity to SFR in small galaxies. The z {approx}> 4 GRB-inferred SFR is higher than the LBG rate, but this difference is difficult to understand, as both methods rely on several modeling assumptions. Using a physically motivated galaxy luminosity function model, with star formation in dark matter halos with virial temperature T{sub vir} {approx}> 2 Multiplication-Sign 10{sup 4} K (M{sub DM} {approx}> 2 Multiplication-Sign 10{sup 8} M{sub Sun }), we show that GRB- and LBG-derived SFRs are consistent if GRBs extend to faint galaxies (M{sub AB} {approx}< -11). To test star formation below the detection limit L{sub lim} {approx} 0.05L*{sub z=3} of LBG surveys, we propose to measure the fraction f{sub det}(L > L{sub lim}, z) of GRB hosts with L > L{sub lim}. This fraction quantifies the missing star formation fraction in LBG surveys, constraining the mass-suppression scale for galaxy formation, with weak dependence on modeling assumptions. Because f{sub det}(L > L{sub lim}, z) corresponds to the ratio of SFRs derived from LBG and GRB surveys, if these estimators are unbiased, measuring f{sub det}(L > L{sub lim}, z) also constrains the redshift evolution of the GRB production rate per unit mass of star formation. Our analysis predicts significant success for GRB host detections at z {approx} 5 with f{sub det}(L > L{sub lim}, z) {approx} 0.4, but rarer detections at z > 6. By analyzing the upper limits on host galaxy luminosities of six z > 5 GRBs from literature data, we infer that galaxies with M{sub AB} > -15 were present at z > 5 at 95% confidence, demonstrating the key role played by very faint galaxies during reionization.

  4. Slow Evolution of the Specific Star Formation Rate at z > 2: The Impact of Dust, Emission Lines, and a Rising Star Formation History

    NASA Astrophysics Data System (ADS)

    González, Valentino; Bouwens, Rychard; Illingworth, Garth; Labbé, Ivo; Oesch, Pascal; Franx, Marijn; Magee, Dan

    2014-01-01

    We measure the evolution of the specific star formation rate (sSFR = SFR/M stellar) between redshift 4 and 6 to assess the reported "constant" sSFR at z > 2. We derive stellar masses and star formation rates (SFRs) for a large sample of 750 z ~ 4-6 galaxies in the GOODS-S field by fitting stellar population models to their spectral energy distributions. Dust extinction is derived from the observed UV colors. We evaluate different star formation histories (SFHs, constant and rising with time) and the impact of optical emission lines. The SFR and M stellar values are insensitive to whether the SFH is constant or rising. The derived sSFR is very similar (within 0.1 dex) in two M stellar bins centered at 1 and 5 × 109 M ⊙. The effect of emission lines was, however, quite pronounced. Assuming no contribution from emission lines, the sSFR for galaxies at 5 × 109 M ⊙ evolves weakly at z > 2 (sSFR(z)vprop(1 + z)0.6 ± 0.1), consistent with previous results. When emission lines are included in the rest-frame optical bands, consistent with the observed Infrared Array Camera [3.6] and [4.5] fluxes, the sSFR shows higher values at high redshift following sSFR(z)vprop(1 + z)1.0 ± 0.1, i.e., the best-fit evolution shows a sSFR ~2.3 × higher at z ~ 6 than at z ~ 2. This is, however, a substantially weaker trend than that found at z < 2 and even than that expected from current models for z > 2 (sSFR(z)vprop(1 + z)2.5). Even accounting for emission lines, the observed sSFR(z) trends at z > 2 are still in tension with theoretical expectations.

  5. Astrophysical reaction rate for Be9 formation within a three-body approach

    NASA Astrophysics Data System (ADS)

    Casal, J.; Rodríguez-Gallardo, M.; Arias, J. M.; Thompson, I. J.

    2014-10-01

    The structure of the Borromean nucleus Be9 (α+α+n) is addressed within a three-body approach using the analytical transformed harmonic oscillator method. The three-body formalism provides an accurate description of the radiative capture reaction rate for the entire temperature range relevant in astrophysics. At high temperatures, results match the calculations based on two-step sequential processes. At low temperatures, where the particles have no access to intermediate two-body resonances, the three-body direct capture leads to reaction rates larger than the sequential processes. These results support the reliability of the method for systems with several charged particles.

  6. Fault Mirror Formation and Destruction Correlates With Slip Rates on Carbonate Faults

    NASA Astrophysics Data System (ADS)

    Siman-Tov, S.; Aharonov, E.; Boneh, Y.; Reches, Z.

    2014-12-01

    Glossy, highly smooth surfaces, recently termed Fault Mirrors (FMs), are commonly observed on exposed fault-zones. At least for carbonate faults, TEM investigation of FMs indicates that they are composed of a thin layer of ultra-fine, nano-size grains (Siman-Tov et al., 2013). Recent carbonate shearing experiments suggest FMs form during seismic slip and may serve as seismic indicators. To explore the formation and destruction of FMs we performed rotary shear experiments on experimental fault surfaces in three types of limestone. The experiments were conducted at slip-velocities ranging between V=0.001-0.7 m/s, and normal stress up to 1.5 MPa. FMs started to develop when the slip velocity exceeded a few cm/s, and fault coverage by FMs increased systematically with velocity, reaching ~ 50% of fault surface at V=0.6 m/s. No FMs developed at V~<3 cm/s, and importantly, pre-existing FMs were destroyed at these low velocities. The measured friction coefficient, μ, was found to be inversely correlated with the FM coverage: μ~0.8 for no-FM, low velocity, and μ~0.4 for 50% FMs coverage at high velocity. The analysis of the experimental thermal conditions and SEM FM images suggests that the FMs form by sintering of gouge nano-grains in a process similar to industrial 'hot pressing'. We propose that formation and destruction of FMs is indicative of a thermally and mechanically controlled brittle-ductile transition: destruction of the highly smoothed fault mirrors is caused by brittle wear at relatively low temperature, while their formation is controlled by ductile deformation at higher temperature. We further suggest that the observed velocity weakening at high velocity is caused by formation of an extremely localized and ductile nano-slip zone that reduces friction. Based on these results we conclude that the presence of fault mirrors along natural carbonate faults indicates that the fault slipped at seismic velocities and had weakened during the slip event, and also in

  7. CONNECTING THE GAMMA RAY BURST RATE AND THE COSMIC STAR FORMATION HISTORY: IMPLICATIONS FOR REIONIZATION AND GALAXY EVOLUTION

    SciTech Connect

    Robertson, Brant E.; Ellis, Richard S.

    2012-01-10

    The contemporary discoveries of galaxies and gamma ray bursts (GRBs) at high redshift have supplied the first direct information on star formation when the universe was only a few hundred million years old. The probable origin of long duration GRBs in the deaths of massive stars would link the universal GRB rate to the redshift-dependent star formation rate (SFR) density, although exactly how is currently unknown. As the most distant GRBs and star-forming galaxies probe the reionization epoch, the potential reward of understanding the redshift-dependent ratio {Psi}(z) of the GRB rate to SFR is significant and includes addressing fundamental questions such as incompleteness in rest-frame UV surveys for determining the SFR at high redshift and time variations in the stellar initial mass function. Using an extensive sample of 112 GRBs above a fixed luminosity limit drawn from the Second Swift Burst Alert Telescope catalog and accounting for uncertainty in their redshift distribution by considering the contribution of 'dark' GRBs, we compare the cumulative redshift distribution N(< z) of GRBs with the star formation density {rho}-dot{sub *}(z) measured from UV-selected galaxies over 0 < z <4. Strong evolution (e.g., {Psi}(z){proportional_to}(1 + z){sup 1.5}) is disfavored (Kolmogorov-Smirnov test P < 0.07). We show that more modest evolution (e.g., {Psi}(z){proportional_to}(1 + z){sup 0.5}) is consistent with the data (P Almost-Equal-To 0.9) and can be readily explained if GRBs occur primarily in low-metallicity galaxies which are proportionally more numerous at earlier times. If such trends continue beyond z {approx_equal} 4, we find that the discovery rate of distant GRBs implies an SFR density much higher than that inferred from UV-selected galaxies. While some previous studies of the GRB-SFR connection have concluded that GRB-inferred star formation at high redshift would be sufficient to maintain cosmic reionization over 6

  8. Quantifying rind formation and chemical weathering rates in weathering clasts with uranium-series isotopes: a case study from Basse-Terre Island, Guadeloupe

    NASA Astrophysics Data System (ADS)

    Ma, L.; Chabaux, F. J.; Pelt, E.; Granet, M.; Sak, P. B.; Gaillardet, J.; Lebedeva, M.; Brantley, S. L.

    2011-12-01

    Weathering of tropical volcanic islands is rapid because of the reactive nature of the volcanic rock and the hot humid climate. In the tropics, rock fragments in the regolith zone commonly form alteration rinds. Weathering rinds are excellent samples to understand key chemical weathering processes. To quantify rock weathering rates in a tropical climate and to understand the environmental factors that control these rates, we combined a novel U-series isotopic technique with chemical and electron microprobe analyses to study weathering rinds formed at Basse-Terre Island, Guadeloupe. U-series isotopes and element concentrations were analyzed in a basaltic/andesitic weathering rind collected from the Bras David watershed on Basse-Terre Island. From the clast, core and rind samples were obtained by drilling along two linear profiles. Elemental profiles reveal that elemental loss varies in the order of Ca, Na, Sr > K, Mg, Rb > Mn > Si > Ba > Al > Fe, and Ti =0 across the core-rind interface, consistent with relative reactivity of phases in the clast from plagioclase ≈ pyroxene ≈ glass matrix > apatite > ilmenite. Elemental profiles also reveal conservative behavior of Th and external addition of U into the rind during clast weathering. Measured (234U/238U) activity ratios of the rind samples (1.001 to 1.031) are mostly higher than the core samples (average at ~1.003). Measured (238U/232Th) and (230Th/232Th) activity ratios of the core and rind samples range from 0.973 to 1.817, and 0.971 to 1.375, respectively. Most importantly, both (238U/232Th) and (230Th/232Th) activity ratios increase systematically from the core into the weathering rind for the two profiles. The elemental profiles and electronic microprobe observations suggest that weathering reactions include dissolution of pyroxene, plagioclase, and glass matrix, and formation of Fe oxyhydroxides, gibbsite and minor kaolinite. The dissolution of plagioclase leads to significant porosity growth within the rind

  9. The Mechanism of Fibril Formation of a Non-inhibitory Serpin Ovalbumin Revealed by the Identification of Amyloidogenic Core Regions*

    PubMed Central

    Tanaka, Naoki; Morimoto, Yumi; Noguchi, Yurika; Tada, Tomoko; Waku, Tomonori; Kunugi, Shigeru; Morii, Takashi; Lee, Yin-Fai; Konno, Takashi; Takahashi, Nobuyuki

    2011-01-01

    Ovalbumin (OVA), a non-inhibitory member of the serpin superfamily, forms fibrillar aggregates upon heat-induced denaturation. Recent studies suggested that OVA fibrils are generated by a mechanism similar to that of amyloid fibril formation, which is distinct from polymerization mechanisms proposed for other serpins. In this study, we provide new insights into the mechanism of OVA fibril formation through identification of amyloidogenic core regions using synthetic peptide fragments, site-directed mutagenesis, and limited proteolysis. OVA possesses a single disulfide bond between Cys73 and Cys120 in the N-terminal helical region of the protein. Heat treatment of disulfide-reduced OVA resulted in the formation of long straight fibrils that are distinct from the semiflexible fibrils formed from OVA with an intact disulfide. Computer predictions suggest that helix B (hB) of the N-terminal region, strand 3A, and strands 4–5B are highly β-aggregation-prone regions. These predictions were confirmed by the fact that synthetic peptides corresponding to these regions formed amyloid fibrils. Site-directed mutagenesis of OVA indicated that V41A substitution in hB interfered with the formation of fibrils. Co-incubation of a soluble peptide fragment of hB with the disulfide-intact full-length OVA consistently promoted formation of long straight fibrils. In addition, the N-terminal helical region of the heat-induced fibril of OVA was protected from limited proteolysis. These results indicate that the heat-induced fibril formation of OVA occurs by a mechanism involving transformation of the N-terminal helical region of the protein to β-strands, thereby forming sequential intermolecular linkages. PMID:21156792

  10. Modeling of the cooling rate effect on the residual stress formation in the cantala fiber/recycled HDPE composites

    NASA Astrophysics Data System (ADS)

    Probotinanto, Yosafat C.; Raharjo, Wijang W.; Budiana, Eko P.

    2016-03-01

    Residual stress has great influence on the mechanical properties of polymer composites. Therefore, its formation during the manufacturing process needs to be investigated. The aim of this study is to investigate the influences of cooling rate on the residual stress distribution of the cantala/rHDPE composite by simulation. The simulation was done by using a SOLID227 element type of ANSYS. The cooling rates that used in this study are 0.5°C/minute, 1°C/minute, and 60°C/minute. The values of the residual stress correspond to the increasing of the cooling rate are 1171.31 kPa, 1171.42 kPa, 1172.36 kPa. In the radial direction, the residual stress was tensile inside the fibers, while in the longitudinal direction, the tensile residual stress occurred in the matrix zones and compressive in the fiber zones.

  11. Action Potential Energetics at the Organismal Level Reveal a Trade-Off in Efficiency at High Firing Rates

    PubMed Central

    Gilmour, Kathleen M.; Moorhead, Mayron J.; Perry, Steve F.; Markham, Michael R.

    2014-01-01

    The energetic costs of action potential (AP) production constrain the evolution of neural codes and brain networks. Cellular-level estimates of AP-related costs are typically based on voltage-dependent Na+ currents that drive active transport by the Na+/K+ ATPase to maintain the Na+ and K+ ion concentration gradients necessary for AP production. However, these estimates of AP cost have not been verified at the organismal level. Electric signaling in the weakly electric fish Eigenmannia virescens requires that specialized cells in an electric organ generate APs with large Na+ currents at high rates (200–600 Hz). We measured these currents using a voltage-clamp protocol and then estimated the energetic cost at the cellular level using standard methods. We then used this energy-intensive signaling behavior to measure changes in whole-animal energetics for small changes in electric discharge rate. At low rates, the whole-animal measure of AP cost was similar to our cellular-level estimates. However, AP cost increased nonlinearly with increasing firing rates. We show, with a biophysical model, that this nonlinearity can arise from the increasing cost of maintaining AP amplitude at high rates. Our results confirm that estimates of energetic costs based on Na+ influx are appropriate for low baseline firing rates, but that extrapolating to high firing rates may underestimate true costs in cases in which AP amplitude does not decrease. Moreover, the trade-off between energetic cost and firing rate suggests an additional constraint on the evolution of high-frequency signaling in neuronal systems. PMID:24381281

  12. Comparison of the aggregation of homologous β2-microglobulin variants reveals protein solubility as a key determinant of amyloid formation

    PubMed Central

    Pashley, Clare L.; Hewitt, Eric W.; Radford, Sheena E.

    2016-01-01

    The mouse and human β2-microglobulin protein orthologs are 70 % identical in sequence and share 88 % sequence similarity. These proteins are predicted by various algorithms to have similar aggregation and amyloid propensities. However, whilst human β2m (hβ2m) forms amyloid-like fibrils in denaturing conditions (e.g. pH 2.5) in the absence of NaCl, mouse β2m (mβ2m) requires the addition of 0.3 M NaCl to cause fibrillation. Here, the factors which give rise to this difference in amyloid propensity are investigated. We utilise structural and mutational analyses, fibril growth kinetics and solubility measurements under a range of pH and salt conditions, to determine why these two proteins have different amyloid propensities. The results show that, although other factors influence the fibril growth kinetics, a striking difference in the solubility of the proteins is a key determinant of the different amyloidogenicity of hβ2m and mβ2m. The relationship between protein solubility and lag time of amyloid formation is not captured by current aggregation or amyloid prediction algorithms, indicating a need to better understand the role of solubility on the lag time of amyloid formation. The results demonstrate the key contribution of protein solubility in determining amyloid propensity and lag time of amyloid formation, highlighting how small differences in protein sequence can have dramatic effects on amyloid formation. PMID:26780548

  13. Comparison of the aggregation of homologous β2-microglobulin variants reveals protein solubility as a key determinant of amyloid formation.

    PubMed

    Pashley, Clare L; Hewitt, Eric W; Radford, Sheena E

    2016-02-13

    The mouse and human β2-microglobulin protein orthologs are 70% identical in sequence and share 88% sequence similarity. These proteins are predicted by various algorithms to have similar aggregation and amyloid propensities. However, whilst human β2m (hβ2m) forms amyloid-like fibrils in denaturing conditions (e.g. pH2.5) in the absence of NaCl, mouse β2m (mβ2m) requires the addition of 0.3M NaCl to cause fibrillation. Here, the factors which give rise to this difference in amyloid propensity are investigated. We utilise structural and mutational analyses, fibril growth kinetics and solubility measurements under a range of pH and salt conditions, to determine why these two proteins have different amyloid propensities. The results show that, although other factors influence the fibril growth kinetics, a striking difference in the solubility of the proteins is a key determinant of the different amyloidogenicity of hβ2m and mβ2m. The relationship between protein solubility and lag time of amyloid formation is not captured by current aggregation or amyloid prediction algorithms, indicating a need to better understand the role of solubility on the lag time of amyloid formation. The results demonstrate the key contribution of protein solubility in determining amyloid propensity and lag time of amyloid formation, highlighting how small differences in protein sequence can have dramatic effects on amyloid formation. PMID:26780548

  14. Rate constant for formation of chlorine nitrate by the reaction ClO + NO2 + M

    NASA Technical Reports Server (NTRS)

    Leu, M. T.; Lin, C. L.; Demore, W. B.

    1977-01-01

    The pseudo-first-order decay of ClO in a large excess of NO2 was monitored in a discharge flow/mass-spectrometer apparatus in order to measure the rate constant of the reaction ClO + NO2 + M yields ClONO2 + M for M = He, Ar, and N2 over the temperature range from 248 to 417 K. Numerical results are given for He at 248, 299, 360, and 417 K (1 to 9 torr); for Ar at 298 K (1 to 4 torr); and for N2 at 299, 360, and 417 K (1 to 6 torr). Systematic errors are estimated, and identification of the reaction product is discussed. The results obtained are shown to be in excellent agreement with other recent measurements of the same rate constant.

  15. The rate of planet formation and the solar system's small bodies

    NASA Technical Reports Server (NTRS)

    Safronov, Viktor S.

    1991-01-01

    The evolution of random velocities and the mass distribution of preplanetary body at the early stage of accumulation are currently under review. Arguments were presented for and against the view of an extremely rapid, runaway growth of the largest bodies at this stage with parameter values of Theta approximately greater than 10(exp 3). Difficulties are encountered assuming such a large Theta: (1) bodies of the Jovian zone penetrate the asteroid zone too late and do not have time to hinder the formation of a normal-sized planet in the asteroidal zone and thereby remove a significant portion of the mass of solid matter and (2) Uranus and Neptune cannot eject bodies from the solar system into the cometary cloud. Therefore, the values Theta less than 10(exp 2) appear to be preferable.

  16. Nanovoid formation in cross-linked epoxy and poly(dicyclopentadiene) networks during high strain rate deformation

    NASA Astrophysics Data System (ADS)

    Elder, Robert M.; Knorr, Daniel B., Jr.; Lenhart, Joseph L.; Andzelm, Jan W.; Sirk, Timothy W.

    2015-03-01

    Cross-linked polymer networks are widely used as structural and protective materials under extremes of temperature, pressure, or strain rate. In particular, substantial effort has been devoted to improving the high strain rate impact resistance of epoxy resins. Although epoxy resins are widely used in applications requiring impact resistance, epoxy resins with the strength and stiffness necessary in structural applications typically have poor toughness. Recent work showed that other chemistries in cross-linked polymers can overcome this trade-off between strength and toughness. Specifically, cross-linked polydicyclopentadiene (pDCPD) was found to have exceptional performance compared to epoxy resins, which is related to the high toughness of pDCPD. Based on the physicochemical properties of epoxy and pDCPD, it was hypothesized that the excellent toughness of pDCPD was due to the formation and growth of nanovoids during impact events. Void growth dissipates energy that otherwise would contribute to failure. We use atomistic molecular dynamics simulations to quantify void formation in these cross-linked polymer networks and to examine the molecular-level properties of the voids. Our findings suggest methods to increase void formation and growth, which may improve toughness.

  17. Spectroelectrochemical investigation of intramolecular and interfacial electron-transfer rates reveals differences between nitrite reductase at rest and during turnover.

    PubMed

    Krzemiński, Łukasz; Ndamba, Lionel; Canters, Gerard W; Aartsma, Thijs J; Evans, Stephen D; Jeuken, Lars J C

    2011-09-28

    A combined fluorescence and electrochemical method is described that is used to simultaneously monitor the type-1 copper oxidation state and the nitrite turnover rate of a nitrite reductase (NiR) from Alcaligenes faecalis S-6. The catalytic activity of NiR is measured electrochemically by exploiting a direct electron transfer to fluorescently labeled enzyme molecules immobilized on modified gold electrodes, whereas the redox state of the type-1 copper site is determined from fluorescence intensity changes caused by Förster resonance energy transfer (FRET) between a fluorophore attached to NiR and its type-1 copper site. The homotrimeric structure of the enzyme is reflected in heterogeneous interfacial electron-transfer kinetics with two monomers having a 25-fold slower kinetics than the third monomer. The intramolecular electron-transfer rate between the type-1 and type-2 copper site changes at high nitrite concentration (≥520 μM), resulting in an inhibition effect at low pH and a catalytic gain in enzyme activity at high pH. We propose that the intramolecular rate is significantly reduced in turnover conditions compared to the enzyme at rest, with an exception at low pH/nitrite conditions. This effect is attributed to slower reduction rate of type-2 copper center due to a rate-limiting protonation step of residues in the enzyme's active site, gating the intramolecular electron transfer. PMID:21863850

  18. Plastid genomes reveal support for deep phylogenetic relationships and extensive rate variation among palms and other commelinid monocots.

    PubMed

    Barrett, Craig F; Baker, William J; Comer, Jason R; Conran, John G; Lahmeyer, Sean C; Leebens-Mack, James H; Li, Jeff; Lim, Gwynne S; Mayfield-Jones, Dustin R; Perez, Leticia; Medina, Jesus; Pires, J Chris; Santos, Cristian; Wm Stevenson, Dennis; Zomlefer, Wendy B; Davis, Jerrold I

    2016-01-01

    Despite progress based on multilocus, phylogenetic studies of the palms (order Arecales, family Arecaceae), uncertainty remains in resolution/support among major clades and for the placement of the palms among the commelinid monocots. Palms and related commelinids represent a classic case of substitution rate heterogeneity that has not been investigated in the genomic era. To address questions of relationships, support and rate variation among palms and commelinid relatives, 39 plastomes representing the palms and related family Dasypogonaceae were generated via genome skimming and integrated within a monocot-wide matrix for phylogenetic and molecular evolutionary analyses. Support was strong for 'deep' relationships among the commelinid orders, among the five palm subfamilies, and among tribes of the subfamily Coryphoideae. Additionally, there was extreme heterogeneity in the plastid substitution rates across the commelinid orders indicated by model based analyses, with c. 22 rate shifts, and significant departure from a global clock. To date, this study represents the most comprehensively sampled matrix of plastomes assembled for monocot angiosperms, providing genome-scale support for phylogenetic relationships of monocot angiosperms, and lays the phylogenetic groundwork for comparative analyses of the drivers and correlates of such drastic differences in substitution rates across a diverse and significant clade. PMID:26350789

  19. Reduction of Tubular Flow Rate as a Mechanism of Oliguria in the Early Phase of Endotoxemia Revealed by Intravital Imaging.

    PubMed

    Nakano, Daisuke; Doi, Kent; Kitamura, Hiroaki; Kuwabara, Takashige; Mori, Kiyoshi; Mukoyama, Masashi; Nishiyama, Akira

    2015-12-01

    Urine output is widely used as a criterion for the diagnosis of AKI. Although several potential mechanisms of septic AKI have been identified, regulation of urine flow after glomerular filtration has not been evaluated. This study evaluated changes in urine flow in mice with septic AKI. The intratubular urine flow rate was monitored in real time by intravital imaging using two-photon laser microscopy. The tubular flow rate, as measured by freely filtered dye (FITC-inulin or Lucifer yellow), time-dependently declined after LPS injection. At 2 hours, the tubular flow rate was slower in mice injected with LPS than in mice injected with saline, whereas BP and GFR were similar in the two groups. Importantly, fluorophore-conjugated LPS selectively accumulated in the proximal tubules that showed reduced tubular flow at 2 hours and luminal obstruction with cell swelling at 24 hours. Delipidation of LPS or deletion of Toll-like receptor 4 in mice abolished these effects, whereas neutralization of TNF-α had little effect on LPS-induced tubular flow retention. Rapid intravenous fluid resuscitation within 6 hours improved the tubular flow rate only when accompanied by the dilation of obstructed proximal tubules with accumulated LPS. These findings suggest that LPS reduces the intratubular urine flow rate during early phases of endotoxemia through a Toll-like receptor 4-dependent mechanism, and that the efficacy of fluid resuscitation may depend on the response of tubules with LPS accumulation. PMID:25855781

  20. iTRAQ-based analysis of developmental dynamics in the soybean leaf proteome reveals pathways associated with leaf photosynthetic rate.

    PubMed

    Qin, Jun; Zhang, Jianan; Liu, Duan; Yin, Changcheng; Wang, Fengmin; Chen, Pengyin; Chen, Hao; Ma, Jinbing; Zhang, Bo; Xu, Jin; Zhang, Mengchen

    2016-08-01

    Photosynthetic rate which acts as a vital limiting factor largely affects the potential of soybean production, especially during the senescence phase. However, the physiological and molecular mechanisms that underlying the change of photosynthetic rate during the developmental process of soybean leaves remain unclear. In this study, we compared the protein dynamics during the developmental process of leaves between the soybean cultivar Hobbit and the high-photosynthetic rate cultivar JD 17 using the iTRAQ (isobaric tags for relative and absolute quantification) method. A total number of 1269 proteins were detected in the leaves of these two cultivars at three different developmental stages. These proteins were classified into nine expression patterns depending on the expression levels at different developmental stages, and the proteins in each pattern were also further classified into three large groups and 20 small groups depending on the protein functions. Only 3.05-6.53 % of the detected proteins presented a differential expression pattern between these two cultivars. Enrichment factor analysis indicated that proteins involved in photosynthesis composed an important category. The expressions of photosynthesis-related proteins were also further confirmed by western blotting. Together, our results suggested that the reduction in photosynthetic rate as well as chloroplast activity and composition during the developmental process was a highly regulated and complex process which involved a serial of proteins that function as potential candidates to be targeted by biotechnological approaches for the improvement of photosynthetic rate and production. PMID:27048574

  1. Potential temperature, upwelling rate and eclogite in the formation of the North Atlantic large igneous province

    NASA Astrophysics Data System (ADS)

    Brown, E. L.; Lesher, C. E.

    2010-12-01

    The volumes and compositions of basalts generated by adiabatic decompression melting of the Earth’s mantle depend on mantle potential temperature (T_P), upwelling rate and the fertility of the mantle source. The relative importance of these factors in generating the high productivity magmatism of the Paleogene - Recent North Atlantic large igneous province (NAIP) remains controversial. Each has been proposed as a primary factor in the region. To assess the significance of these mechanisms in NAIP magmatism, we apply our forward melting model, REEBOX PRO, which simulates the melting of a heterogeneous source comprised of peridotite and eclogite lithologies. The model accounts for the thermodynamics of adiabatic decompression melting of a heterogeneous source using constraints from laboratory melting experiments. Input values of T_P and eclogite abundance are used to calculate the buoyancy of the mantle source and maximum upwelling rates. Source buoyancy constrains the maximum amount of eclogite in the mantle source that can ascend beneath the rift axis. All melts generated within the melting regime are pooled to form magmatic crust according to the residual column method. Using the model, variations in magmatic crustal thickness (from geophysics) as a function of eclogite content (from geochemistry) can be related to T_P and upwelling rate. Models with no thermal anomaly, that call on either enhanced upwelling rates due to plate separation (edge - driven convection) or the melting of abundant (> 30%) eclogite at “ambient” T_P (1325 °C), cannot generate the observed igneous crustal thicknesses around the province. Rather, elevated mantle T_P (minimum thermal anomaly ~ 85 - 195 °C) and associated buoyancy - driven upwelling are needed to explain the volume of igneous crust in the province. Involvement of eclogite, while necessary to explain the compositions of many NAIP lavas, does not significantly enhance melt production. These factors, coupled with the long

  2. Rate of Biochemical oxygen demand during formation of hypoxia in Amur Bay, Sea of Japan

    NASA Astrophysics Data System (ADS)

    Tishchenko, P. P.; Tishchenko, P. Ya.; Zvalinskii, V. I.; Semkin, P. Yu.

    2014-12-01

    In May 2011, a Water Quality Monitor (WQM) hydrological station was maintained in the hypoxia area of Amur Bay one meter above the bottom, at the depth of 19 m. The temperature, electric conductivity, pressure, and content of dissolved oxygen were registered every four hours for more than three months. On the basis of these data, it was found that the period of hypoxia at the observation point lasted 93 days and a model of calculation of the rate of biochemical oxygen demand and the velocity of ventilation of the bottom waters is suggested.

  3. Formation of fine particle emulsions by high-dose-rate polymerization

    SciTech Connect

    Hayashi, K.; Kijima, T.; Okamura, S.; Egusa, S.; Makuuchi, K.

    1982-12-01

    Emulsion of chloroprene, acrylic acid, styrene, n-butyl methacrylate, and 2-hydroxyethyl methacrylate monomers mixed with sodium lauryl sulfate as an emulsifier were polymerized or copolymerized in a flow system for control of temperature and for mixing of the emulsion under irradiation. Electron beams of a dose rate of 0.1 to 10 Mrad/s was used as a radiation source to produce very fine particle emulsions. Significant decreases in particle diameter were noted for polymers aged for as much as 5 weeks. (BLM)

  4. Star-formation rates, molecular clouds, and the origin of the far-infrared luminosity of isolated and interacting galaxies

    NASA Technical Reports Server (NTRS)

    Solomon, P. M.; Sage, L. J.

    1988-01-01

    The CO luminosities of 93 galaxies have been determined and are compared with their IRAS FIR luminosities. Strongly interacting/merging galaxies have L(FIR)/L(CO) substantially higher than that of isolated galaxies or galactic giant molecular clouds (GMCs). Galaxies with tidal tails/bridges are the most extreme type with L(FIR)/L(CO) nine times as high as isolated galaxies. Interactions between close pairs of galaxies do not have much effect on the molecular content and global star-formation rate. If the high ratio L(FIR)/L(CO) in strongly interacting galaxies is due to star formation then the efficiency of this process is higher than that of any galactic GMC. Isolated galaxies, distant pairs, and close pairs have an FIR/CO luminosity ratio which is within a factor of two of galactic GMCs with H II regions. The CO luminosities of FIR-luminous galaxies are among the highest observed for any spiral galaxies.

  5. ZFOURGE catalogue of AGN candidates: an enhancement of 160-μm-derived star formation rates in active galaxies to z = 3.2

    NASA Astrophysics Data System (ADS)

    Cowley, Michael J.; Spitler, Lee R.; Tran, Kim-Vy H.; Rees, Glen A.; Labbé, Ivo; Allen, Rebecca J.; Brammer, Gabriel B.; Glazebrook, Karl; Hopkins, Andrew M.; Juneau, Stéphanie; Kacprzak, Glenn G.; Mullaney, James R.; Nanayakkara, Themiya; Papovich, Casey; Quadri, Ryan F.; Straatman, Caroline M. S.; Tomczak, Adam R.; van Dokkum, Pieter G.

    2016-03-01

    We investigate active galactic nuclei (AGN) candidates within the FourStar Galaxy Evolution Survey (ZFOURGE) to determine the impact they have on star formation in their host galaxies. We first identify a population of radio, X-ray, and infrared-selected AGN by cross-matching the deep Ks-band imaging of ZFOURGE with overlapping multiwavelength data. From this, we construct a mass-complete (log(M_{{*}}/M_{{⊙}}) ≥9.75), AGN luminosity limited sample of 235 AGN hosts over z = 0.2-3.2. We compare the rest-frame U - V versus V - J (UVJ) colours and specific star formation rates (sSFRs) of the AGN hosts to a mass-matched control sample of inactive (non-AGN) galaxies. UVJ diagnostics reveal AGN tend to be hosted in a lower fraction of quiescent galaxies and a higher fraction of dusty galaxies than the control sample. Using 160 μm Herschel PACS data, we find the mean specific star formation rate of AGN hosts to be elevated by 0.34 ± 0.07 dex with respect to the control sample across all redshifts. This offset is primarily driven by infrared-selected AGN, where the mean sSFR is found to be elevated by as much as a factor of ˜5. The remaining population, comprised predominantly of X-ray AGN hosts, is found mostly consistent with inactive galaxies, exhibiting only a marginal elevation. We discuss scenarios that may explain these findings and postulate that AGN are less likely to be a dominant mechanism for moderating galaxy growth via quenching than has previously been suggested.

  6. The Concordance Cosmic Star Formation Rate: Implications from and for the supernova neutrino and gamma ray backgrounds

    SciTech Connect

    Strigari, Louis E.; Beacom, John F.; Walker, Terry P.; Zhang, Pengjie; /Fermilab

    2005-02-01

    We constrain the Cosmic Star Formation Rate (CSFR) by requiring that massive stars produce the observed UV, optical, and IR light while at the same time not overproduce the Diffuse Supernova Neutrino Background as bounded by Super-Kamiokande. With the massive star component so constrained we then show that a reasonable choice of stellar Initial Mass Function and other parameters results in SNIa rates and iron yields in good agreement with data. In this way we define a ''concordance'' CSFR that predicts the optical SNII rate and the SNIa contribution to the MeV Cosmic Gamma-Ray Background. The CSFR constrained to reproduce these and other proxies of intermediate and massive star formation is more clearly delineated than if it were measured by any one technique and has the following testable consequences: (1) SNIa contribute only a small fraction of the MeV Cosmic Gamma-Ray Background, (2) massive star core-collapse is nearly always accompanied by a successful optical SNII, and (3) the Diffuse Supernova Neutrino Background is tantalizingly close to detectability.

  7. Nucleation-dependent tau filament formation: the importance of dimerization and an estimation of elementary rate constants.

    PubMed

    Congdon, Erin E; Kim, Sohee; Bonchak, Jonathan; Songrug, Tanakorn; Matzavinos, Anastasios; Kuret, Jeff

    2008-05-16

    Filamentous inclusions composed of the microtubule-associated protein tau are found in Alzheimer disease and other tauopathic neurodegenerative diseases, but the mechanisms underlying their formation from full-length protein monomer under physiological conditions are unclear. To address this issue, the fibrillization of recombinant full-length four-repeat human tau was examined in vitro as a function of time and submicromolar tau concentrations using electron microscopy assay methods and a small-molecule inducer of aggregation, thiazine red. Data were then fit to a simple homogeneous nucleation model with rate constant constraints established from filament dissociation rate, critical concentration, and mass-per-unit length measurements. The model was then tested by comparing the predicted time-dependent evolution of length distributions to experimental data. Results indicated that once assembly-competent conformations were attained, the rate-limiting step in the fibrillization pathway was tau dimer formation. Filament elongation then proceeded by addition of tau monomers to nascent filament ends. Filaments isolated at reaction plateau contained approximately 2 tau protomers/beta-strand spacing on the basis of mass-per-unit length measurements. The model suggests four key steps in the aggregation pathway that must be surmounted for tau filaments to form in disease. PMID:18359772

  8. Transcriptome analysis of grain-filling caryopses reveals involvement of multiple regulatory pathways in chalky grain formation in rice

    PubMed Central

    2010-01-01

    Background Grain endosperm chalkiness of rice is a varietal characteristic that negatively affects not only the appearance and milling properties but also the cooking texture and palatability of cooked rice. However, grain chalkiness is a complex quantitative genetic trait and the molecular mechanisms underlying its formation are poorly understood. Results A near-isogenic line CSSL50-1 with high chalkiness was compared with its normal parental line Asominori for grain endosperm chalkiness. Physico-biochemical analyses of ripened grains showed that, compared with Asominori, CSSL50-1 contains higher levels of amylose and 8 DP (degree of polymerization) short-chain amylopectin, but lower medium length 12 DP amylopectin. Transcriptome analysis of 15 DAF (day after flowering) caryopses of the isogenic lines identified 623 differential expressed genes (P < 0.01), among which 324 genes are up-regulated and 299 down-regulated. These genes were classified into 18 major categories, with 65.3% of them belong to six major functional groups: signal transduction, cell rescue/defense, transcription, protein degradation, carbohydrate metabolism and redox homeostasis. Detailed pathway dissection demonstrated that genes involved in sucrose and starch synthesis are up-regulated, whereas those involved in non-starch polysaccharides are down regulated. Several genes involved in oxidoreductive homeostasis were found to have higher expression levels in CSSL50-1 as well, suggesting potential roles of ROS in grain chalkiness formation. Conclusion Extensive gene expression changes were detected during rice grain chalkiness formation. Over half of these differentially expressed genes are implicated in several important categories of genes, including signal transduction, transcription, carbohydrate metabolism and redox homeostasis, suggesting that chalkiness formation involves multiple metabolic and regulatory pathways. PMID:21192807

  9. Rates of utilization of glucose, glutamine and oleate and formation of end-products by mouse peritoneal macrophages in culture.

    PubMed Central

    Newsholme, P; Newsholme, E A

    1989-01-01

    1. The metabolism of mouse thioglycollate-elicited peritoneal macrophages was studied in culture for up to 96 h. 2. The rates of glycolysis, lactate formation and glutamine utilization were approximately linear with time for at least 80 h of culture. 3. The rates of glucose and glutamine utilization by cultured macrophages were approx. 500 and 90 nmol/h per mg of protein respectively. This rate of glucose utilization is at least 50% greater than that previously reported for macrophages during 60 min incubation in a shaking flask; and it is now increased by addition of glutamine to the culture medium. The rate of glutamine utilization in culture is similar to that previously reported for macrophages during 60 min incubation. The major end-product of glucose metabolism is lactate, and those of glutamine metabolism are CO2, glutamate, ammonia and alanine. 4. Oleate was utilized by these cells: 14C from [14C]oleate was incorporated into CO2 and cellular lipid. The highest rate of oleate utilization was observed when both glucose and glutamine were present in the culture medium. The presence of oleate in the culture medium did not affect the rates of utilization of either glucose or glutamine. Of the [14C]oleate incorporated into lipid, approx. 80% was incorporated into triacylglycerol and only 18% into phospholipid. 5. The turnover rate for the total ATP content of the macrophage in culture is about 10 times per minute: the value for the perfused isolated maximally working rat heart is 22. This indicates a high metabolic rate for macrophages, and consequently emphasizes the importance of the provision of fuels for their function in an immune response. PMID:2775207

  10. On the temperature dependence of the rate coefficient of formation of C2+ from C + CH+

    NASA Astrophysics Data System (ADS)

    Rampino, S.; Pastore, M.; Garcia, E.; Pacifici, L.; Laganà, A.

    2016-08-01

    We carry out quasi-classical trajectory calculations for the C + CH+→ C_2^+ + H reaction on an ad hoc computed high-level ab initio potential energy surface. Thermal rate coefficients at the temperatures of relevance in cold interstellar clouds are derived and compared with the assumed, temperature-independent estimates publicly available in kinetic data bases KIDA and UDfA. For a temperature of 10 K the data base value overestimates by a factor of 2 the one obtained by us (thus improperly enhancing the destruction route of CH+ in astrochemical kinetic models) which is seen to double in the temperature range 5-300 K with a sharp increase in the first 50 K. The computed values are fitted via the popular Arrhenius-Kooij formula and best-fitting parameters α = 1.32 × 10-9 cm3 s-1, β = 0.1 and γ = 2.19 K to be included in the online mentioned data bases are provided. Further investigation shows that the temperature dependence of the thermal rate coefficient better conforms to the recently proposed so-called `deformed Arrhenius' law by Aquilanti and Mundim.

  11. Hα Star-Formation Rates for the z=0.84 Galaxy Cluster CLJ0023+0423B

    NASA Astrophysics Data System (ADS)

    Finn, R. A.; Zaritsky, D.; McCarthy, D. W., Jr.

    2003-12-01

    We present Hα -derived star-formation rates (SFRs) for the galaxy cluster CL J0023+0423B at z = 0.845. Our 3σ flux limits corresponds to a star-formation rate of 0.24 h100-2 M⊙ yr-1, and our minimum reliable Hα + [N II] equivalent width is > 10 Å, demonstrating that near-infrared narrow-band imaging can sample the star-forming galaxy population in distant clusters. Comparison with spectroscopy shows that the number of false detections is low (9 ± 6%) and that our Hα equivalent widths are correlated with spectroscopically determined [O II] equivalent widths. A magnitude-limited spectroscopic survey conducted over the same area missed 70% of the star-forming galaxies and 65% of the integrated star formation. Using Hubble Space Telescope Wide Field Planetary Camera 2 Archive images, we fit Sersic profiles to all galaxies with significant narrow-band equivalent widths and find that equivalent width decreases as the steepness of galaxy profile increases. We find no significant population of early type galaxies with ongoing star formation. The integrated SFR per cluster mass of CLJ0023+0423B is a factor of ten higher than that of the three z ˜ 0.2 clusters in the literature with available Hα observations. A larger sample of z ˜ 0.8 clusters spanning a range of cluster masses is needed to determine whether this variation is due to a difference in cluster mass or redshift. RAF acknowledges support from the NASA Graduate Student Researchers Program through NASA Training Grant NGT5-50283 and from an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-0301328. DZ acknowledges support from the David and Lucile Packard Fellowship.

  12. Evolution of star formation in the UKIDSS Ultra Deep Survey field - I. Luminosity functions and cosmic star formation rate out to z = 1.6

    NASA Astrophysics Data System (ADS)

    Drake, Alyssa B.; Simpson, Chris; Collins, Chris A.; James, Phil A.; Baldry, Ivan K.; Ouchi, Masami; Jarvis, Matt J.; Bonfield, David G.; Ono, Yoshiaki; Best, Philip N.; Dalton, Gavin B.; Dunlop, James S.; McLure, Ross J.; Smith, Daniel J. B.

    2013-07-01

    We present new results on the cosmic star formation history in the Subaru/XMM-Newton Deep Survey (SXDS)-Ultra Deep Survey (UDS) field out to z = 1.6. We compile narrow-band data from the Subaru Telescope and the Visible and Infrared Survey Telescope for Astronomy (VISTA) in conjunction with broad-band data from the SXDS and UDS, to make a selection of 5725 emission-line galaxies in 12 redshift slices, spanning 10 Gyr of cosmic time. We determine photometric redshifts for the sample using 11-band photometry, and use a spectroscopically confirmed subset to fine tune the resultant redshift distribution. We use the maximum-likelihood technique to determine luminosity functions in each redshift slice and model the selection effects inherent in any narrow-band selection statistically, to obviate the retrospective corrections ordinarily required. The deep narrow-band data are sensitive to very low star formation rates (SFRs), and allow an accurate evaluation of the faint end slope of the Schechter function, α. We find that α is particularly sensitive to the assumed faintest broad-band magnitude of a galaxy capable of hosting an emission line, and propose that this limit should be empirically motivated. For this analysis, we base our threshold on the limiting observed equivalent widths of emission lines in the local Universe. We compute the characteristic SFR of galaxies in each redshift slice, and the integrated SFR density, ρSFR. We find our results to be in good agreement with the literature and parametrize the evolution of the SFR density as ρSFR ∝ (1 + z)4.58 confirming a steep decline in star formation activity since z ˜ 1.6.

  13. An uncertainty framework to estimate dense water formation rates : case study in the Northwestern Mediterranean.

    NASA Astrophysics Data System (ADS)

    Waldman, Robin; Somot, Samuel; Herrmann, Marine; Sevault, Florence; Estournel, Claude; Testor, Pierre

    2015-04-01

    The Northwestern Mediterranean (NWMed) sea is a key region for the Mediterranean thermohaline circulation as it includes the main deep water formation sites of the Western Mediterranean. The Mediterranean Ocean Observing System for the Environment (MOOSE) has been implemented since 2007 over that region to characterize the space and time variability of the main water masses up to interannual (yearly summer cruises) scale. However, despite a large covering of the NWMed region, the limited number of conductivity, temperature and depth (CTD) casts leads to subsampling errors and advocates for an uncertainty assessment of large-scale hydrology estimates. This study aims at estimating the error related to subsampling in time and space. For that purpose, an Observing System Simulation Experiment (OSSE) is performed with an eddy-permitting Mediterranean sea model (NEMOMED12) and an eddy-resolving NWMed sea model (SYMPHONIE). A subsampling of the full model fields in time and space allows for an error estimate in terms of large-scale hydrology. The methodology is applied to dense water volume estimates for the period july 2012 - july 2013. Secondly, an optimization framework is proposed to evaluate and improve MOOSE network's performances under a series of scientific constraints. The results will be discussed for an application in MOOSE observing network, as well as the main assumptions, the stakes and limitations of this framework.

  14. Formation Rate-Limited Pharmacokinetics of Biologically Active Epoxy Transformers of Prodrug Treosulfan.

    PubMed

    Romański, Michał; Kasprzyk, Anna; Karbownik, Agnieszka; Szałek, Edyta; Główka, Franciszek K

    2016-05-01

    A prodrug treosulfan (TREO) is being evaluated in clinical trials as a myeloablative agent before hematopoietic stem cell transplantation. The active derivatives of TREO, monoepoxide (EBDM), and diepoxide (DEB) are formed in a pH-dependent nonenzymatic reaction. The aim of the study was to investigate pharmacokinetics of the TREO epoxy transformers in a rabbit model and explain the causes of low plasma concentrations of EBDM and DEB observed in patients receiving high-dose TREO before hematopoietic stem cell transplantation. New Zealand white rabbits (n = 5 per cohort) received an intravenous infusion of TREO (group I), injection of DEB (group II), and injection of a solution containing EBDM (group III). When EBDM and DEB were administered to the rabbits, they underwent a very rapid elimination (half-life 0.069 and 0.046 h) associated with a high systemic clearance (10.0 and 14.0 L h(-1) kg(-1)). After administration of TREO, the t1/2 of EBDM was statistically equal to the t1/2 of the prodrug (1.6 h). To conclude, after administration of TREO, its epoxy transformers demonstrate a formation-limited elimination. Then EBDM and DEB have the same elimination half-life as TREO, but the levels of EBDM and DEB in the body, including plasma, are much lower than TREO on account of their inherently high clearance. PMID:27044946

  15. Pore-scale insights to the rate of organic carbon degradation and biofilm formation under variable hydro-biogeochemical conditions in soils and sediments

    NASA Astrophysics Data System (ADS)

    Liu, C.; Yan, Z.; Liu, Y.; Li, M.; Bailey, V. L.

    2015-12-01

    Biogeochemical processes that control microbial growth, organic carbon degradation, and CO2 production and migration are fundamentally occur at the pore scale. In this presentation, we will describe our recent results of a pore-scale simulation research to investigate: 1) how moisture content and distribution affects oxygen delivery, organic carbon availability, and microbial activities that regulate the rate of organic carbon degradation and CO2 production in aerobic systems; and 2) how pore-scale reactive transport processes affect local microbial growth, biofilm formation, and overall rate of microbial reactions in anoxic systems. The results revealed that there is an optimal moisture content for aerobic bacterial respiration and CO2 production. When moisture is below the optimal value, organic carbon availability limits its degradation due to diffusion and osmotic stress to bacterial reactivity; and when moisture is above the optimal value, oxygen delivery limits microbial respiration. The optimal moisture condition is, however, a function of soil texture and physical heterogeneity, bioavailable soil organic carbon, and microbial community function. In anoxic and saturated system, simulation results show that biofilm preferentially forms in concave areas around sand particles and macro aggregates where cross-directional fluxes of organic carbon and electron acceptors (e.g., nitrate) favor microbial growth and attachment. The results provide important insights to the establishment of constitutive relationships between the macroscopic rates of soil organic carbon degradation and moisture content, and to the development of biogeochemical reactive transport models that incorporate biofilm structures and physio-chemical heterogeneity in soils and sediments.

  16. Controlling growth rate anisotropy for formation of continuous ZnO thin films from seeded substrates.

    PubMed

    Zhang, R H; Slamovich, E B; Handwerker, C A

    2013-05-17

    Solution-processed zinc oxide (ZnO) thin films are promising candidates for low-temperature-processable active layers in transparent thin film electronics. In this study, control of growth rate anisotropy using ZnO nanoparticle seeds, capping ions, and pH adjustment leads to a low-temperature (90 ° C) hydrothermal process for transparent and high-density ZnO thin films. The common 1D ZnO nanorod array was grown into a 2D continuous polycrystalline film using a short-time pure solution method. Growth rate anisotropy of ZnO crystals and the film morphology were tuned by varying the chloride (Cl(-)) ion concentration and the initial pH of solutions of zinc nitrate and hexamethylenetetramine (HMTA), and the competitive adsorption effects of Cl(-) ions and HMTA ligands on the anisotropic growth behavior of ZnO crystals were proposed. The lateral growth of nanorods constituting the film was promoted by lowering the solution pH to accelerate the hydrolysis of HMTA, thereby allowing the adsorption effects from Cl(-) to dominate. By optimizing the growth conditions, a dense ∼100 nm thickness film was fabricated in 15 min from a solution of [Cl(-)]/[Zn(2+)] = 1.5 and pH=  4.8 ± 0.1. This film shows >80% optical transmittance and a field-effect mobility of 2.730 cm(2) V(-1) s(-1) at zero back-gate bias. PMID:23595114

  17. Slow evolution of the specific star formation rate at z > 2: the impact of dust, emission lines, and a rising star formation history

    SciTech Connect

    González, Valentino; Illingworth, Garth; Oesch, Pascal; Magee, Dan; Bouwens, Rychard; Labbé, Ivo; Franx, Marijn

    2014-01-20

    We measure the evolution of the specific star formation rate (sSFR = SFR/M {sub stellar}) between redshift 4 and 6 to assess the reported 'constant' sSFR at z > 2. We derive stellar masses and star formation rates (SFRs) for a large sample of 750 z ∼ 4-6 galaxies in the GOODS-S field by fitting stellar population models to their spectral energy distributions. Dust extinction is derived from the observed UV colors. We evaluate different star formation histories (SFHs, constant and rising with time) and the impact of optical emission lines. The SFR and M {sub stellar} values are insensitive to whether the SFH is constant or rising. The derived sSFR is very similar (within 0.1 dex) in two M {sub stellar} bins centered at 1 and 5 × 10{sup 9} M {sub ☉}. The effect of emission lines was, however, quite pronounced. Assuming no contribution from emission lines, the sSFR for galaxies at 5 × 10{sup 9} M {sub ☉} evolves weakly at z > 2 (sSFR(z)∝(1 + z){sup 0.6} {sup ±} {sup 0.1}), consistent with previous results. When emission lines are included in the rest-frame optical bands, consistent with the observed Infrared Array Camera [3.6] and [4.5] fluxes, the sSFR shows higher values at high redshift following sSFR(z)∝(1 + z){sup 1.0} {sup ±} {sup 0.1}, i.e., the best-fit evolution shows a sSFR ∼2.3 × higher at z ∼ 6 than at z ∼ 2. This is, however, a substantially weaker trend than that found at z < 2 and even than that expected from current models for z > 2 (sSFR(z)∝(1 + z){sup 2.5}). Even accounting for emission lines, the observed sSFR(z) trends at z > 2 are still in tension with theoretical expectations.

  18. Revealing rate-limiting steps in complex disease biology: The crucial importance of studying rare, extreme-phenotype families.

    PubMed

    Chakravarti, Aravinda; Turner, Tychele N

    2016-06-01

    The major challenge in complex disease genetics is to understand the fundamental features of this complexity and why functional alterations at multiple independent genes conspire to lead to an abnormal phenotype. We hypothesize that the various genes involved are all functionally united through gene regulatory networks (GRN), and that mutant phenotypes arise from the consequent perturbation of one or more rate-limiting steps that affect the function of the entire GRN. Understanding a complex phenotype thus entails unraveling the details of each GRN, namely, the transcription factors that bind to cis regulatory elements affected by sequence variants altering transcription of specific genes, and their mutual feedback relationships. These GRNs can be identified through their rate-limiting steps and are best uncovered by genomic analyses of rare, extreme phenotype families, thus providing a coherent molecular basis to complex traits and disorders. PMID:27062178

  19. Multigenerational exposure to ocean acidification during food limitation reveals consequences for copepod scope for growth and vital rates.

    PubMed

    Pedersen, Sindre A; Håkedal, Ole Jacob; Salaberria, Iurgi; Tagliati, Alice; Gustavson, Liv Marie; Jenssen, Bjørn Munro; Olsen, Anders J; Altin, Dag

    2014-10-21

    The copepod Calanus finmarchicus is a key component of northern Atlantic food webs, linking energy-transfer from phytoplankton to higher trophic levels. We examined the effect of different ocean acidification (OA) scenarios (i.e., ambient, 1080, 2080, and 3080 μatm CO2) over two subsequent generations under limited food availability. Determination of metabolic and feeding rates, and estimations of the scope for growth, suggests that negative effects observed on vital rates (ontogenetic development, somatic growth, fecundity) may be a consequence of energy budget constraints due to higher maintenance costs under high pCO2-environments. A significant delay in development rate among the parental generation animals exposed to 2080 μatm CO2, but not in the following F1 generation under the same conditions, suggests that C. finmarchicus may have adaptive potential to withstand the direct long-term effects of even the more pessimistic future OA scenarios but underlines the importance of transgenerational experiments. The results also indicate that in a more acidic ocean, increased energy expenditure through rising respiration could lower the energy transfer to higher trophic levels and thus hamper the productivity of the northern Atlantic ecosystem. PMID:25225957

  20. Analysis of Candida albicans Mutants Defective in the Cdk8 Module of Mediator Reveal Links between Metabolism and Biofilm Formation

    PubMed Central

    Lindsay, Allia K.; Morales, Diana K.; Liu, Zhongle; Grahl, Nora; Zhang, Anda; Willger, Sven D.; Myers, Lawrence C.; Hogan, Deborah A.

    2014-01-01

    Candida albicans biofilm formation is a key virulence trait that involves hyphal growth and adhesin expression. Pyocyanin (PYO), a phenazine secreted by Pseudomonas aeruginosa, inhibits both C. albicans biofilm formation and development of wrinkled colonies. Using a genetic screen, we identified two mutants, ssn3Δ/Δ and ssn8Δ/Δ, which continued to wrinkle in the presence of PYO. Ssn8 is a cyclin-like protein and Ssn3 is similar to cyclin-dependent kinases; both proteins are part of the heterotetrameric Cdk8 module that forms a complex with the transcriptional co-regulator, Mediator. Ssn3 kinase activity was also required for PYO sensitivity as a kinase dead mutant maintained a wrinkled colony morphology in the presence of PYO. Furthermore, similar phenotypes were observed in mutants lacking the other two components of the Cdk8 module—Srb8 and Srb9. Through metabolomics analyses and biochemical assays, we showed that a compromised Cdk8 module led to increases in glucose consumption, glycolysis-related transcripts, oxidative metabolism and ATP levels even in the presence of PYO. In the mutant, inhibition of respiration to levels comparable to the PYO-treated wild type inhibited wrinkled colony development. Several lines of evidence suggest that PYO does not act through Cdk8. Lastly, the ssn3 mutant was a hyperbiofilm former, and maintained higher biofilm formation in the presence of PYO than the wild type. Together these data provide novel insights into the role of the Cdk8 module of Mediator in regulation of C. albicans physiology and the links between respiratory activity and both wrinkled colony and biofilm development. PMID:25275466

  1. Ancient and recent clay formation on Mars as revealed from a global survey of hydrous minerals in crater central peaks

    NASA Astrophysics Data System (ADS)

    Sun, Vivian Z.; Milliken, Ralph E.

    2015-12-01

    Clay minerals on Mars have commonly been interpreted as the remnants of pervasive water-rock interaction during the Noachian period (>3.7 Ga). This history has been partly inferred by observations of clays in central peaks of impact craters, which often are presumed uplifted from depth. However, combined mineralogical and morphological analyses of individual craters have shown that some central peak clays may represent post-impact, possibly authigenic processes. Here we present a global survey of 633 central peaks to assess their hydrous minerals and the prevalence of uplifted, detrital, and authigenic clays. Central peak regions are examined using high-resolution Compact Reconnaissance Imaging Spectrometer for Mars and High Resolution Imaging Science Experiment data to identify hydrous minerals and place their detections in a stratigraphic and geologic context. We find that many occurrences of Fe/Mg clays and hydrated silica are associated with potential impact melt deposits. Over 35% of central peak clays are not associated with uplifted rocks; thus, caution must be used when inferring deeper crustal compositions from surface mineralogy of central peaks. Uplifted clay-bearing rocks suggest the Martian crust hosts clays to depths of at least 7 km. We also observe evidence for increasing chloritization with depth, implying the presence of fluids in the upper portions of the crust. Our observations are consistent with widespread Noachian/Early Hesperian clay formation, but a number of central peak clays are also suggestive of clay formation during the Amazonian. These results broadly support current paradigms of Mars' aqueous history while adding insight to global crustal and diagenetic processes associated with clay mineral formation and stability.

  2. Gingival fibromatosis with significant de novo formation of fibrotic tissue and a high rate of recurrence.

    PubMed

    Gawron, Katarzyna; Łazarz-Bartyzel, Katarzyna; Fertala, Andrzej; Plakwicz, Paweł; Potempa, Jan; Chomyszyn-Gajewska, Maria

    2016-01-01

    BACKGROUND Hereditary gingival fibromatosis is characterized by slowly progressive enlargement of the gingiva that can present as an isolated condition or present as part of various syndromes. CASE REPORT An 11-year-old female reported with a gingival lesion that caused masticatory problems and poor oral hygiene. Periodontal examination revealed a dense tissue covering 30% of her teeth crowns within both jaws. Panoramic x-ray showed a normal bone height and teeth positioning. The patient did not use any medications, but a similar condition was also present in other family members. The patient was diagnosed with hereditary gingival fibromatosis. Surgery was carried out to remove excess of gingival tissue. Post-surgical healing was uneventful, but four weeks after the first surgery, the condition recurred amounting to 45% of the initial tissue volume presenting in the mandible, and 25% in the maxilla. Two months later, no significant growth was noted in the mandible, while in the maxilla, growth increased to 40% of the preoperative state. Analysis by polarized microscope showed a significant increase of thin fibrotic fibrils that contributed 80% of the total pool of collagen fibrils in the patient's gingiva, but only 25% in healthy gingiva. The patient was receiving outpatient care for follow-up every three months and surgical intervention had not been planned as long as her periodontal health was not be compromised.  CONCLUSIONS It is currently not clear whether the extent of the fibrosis had a mechanistic association with the ratio of gingival tissue re-growth in our case study. Further studies are needed to explain this association and improve the management of this condition. PMID:27609299

  3. Estimating The CO2 Sequestration Capacity of Fractured Shale Formations Using Methane Production Rates: The Case of the Utica Shale

    NASA Astrophysics Data System (ADS)

    Tao, Z.; Clarens, A. F.

    2014-12-01

    Fractured shale formations that have been drained of hydrocarbons could serve as attractive sites for geologic sequestration of CO2. Shales preferentially sorb CO2 enabling greater storage potential than would be expected based only on the pores vacated during CH4 production. Sequestration in shales could have a variety of other benefits because the intrinsically low permeability of the rock could help mitigate leakage risks and infrastructure resources could be leveraged to minimize costs. Here a modeling framework developed by the authors to estimate the sequestration capacity of fractured shale formations based on CH4 production rates was applied to the Utica Shale. The model is based on a unipore transport model, which assumes that diffusion of gases into and out of the kerogen matrix will control gas transport. The results from the Utica formation were compared to estimates for sequestration in the Marcellus shale to understand how the petrophysical characteristics of these two formations impact estimated sequestration capacity. A detailed sensitivity analysis was carried out to link modeling assumptions and key parameters with known physicochemical characteristics of these two shale formations. Modeling parameters were derived from published production data obtained from the state of Ohio. The model was found to be most sensitive to the equilibrium sorption parameters of CH4 and CO2, for which there is good literature data available. Published values for CO2 sorption varied considerably based on the composition of the shale. Improved experimental data is needed to provide the most accurate estimates of storage in different formations. Differences were observed in gas diffusivity estimates for the Marcellus and Utica shale that could be understood in terms of the petrophysical characteristics of the two formations. We also found important effects tied to the effective diffusion length out of an average pore in the kerogen. These results allow us to understand

  4. Regulation of Star Formation Rates in Multiphase Galactic Disks: Numerical Tests of the Thermal/Dynamical Equilibrium Model

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Goo; Kim, Woong-Tae; Ostriker, Eve C.

    2011-12-01

    We use vertically resolved numerical hydrodynamic simulations to study star formation and the interstellar medium (ISM) in galactic disks. We focus on outer-disk regions where diffuse H I dominates, with gas surface densities Σ = 3-20 M⊙ pc-2 and star-plus-dark matter volume densities ρsd = 0.003-0.5 M⊙ pc-3. Star formation occurs in very dense, self-gravitating clouds that form by mergers of smaller cold cloudlets. Turbulence, driven by momentum feedback from supernova events, destroys bound clouds and puffs up the disk vertically. Time-dependent radiative heating (FUV from recent star formation) offsets gas cooling. We use our simulations to test a new theory for self-regulated star formation. Consistent with this theory, the disks evolve to a state of vertical dynamical equilibrium and thermal equilibrium with both warm and cold phases. The range of star formation surface densities and midplane thermal pressures is ΣSFR ∼ 10-4 to 10-2 M⊙ kpc-2 yr-1 and P th/k B ∼ 102 to 104 cm-3 K. In agreement with observations, turbulent velocity dispersions are ~7 km s-1 and the ratio of the total (effective) to thermal pressure is Ptot/Pth ∼ 4-5, across this whole range (provided shielding is similar to the solar neighborhood). We show that ΣSFR is not well correlated with Σ alone, but rather with Σ ρsd1/2, because the vertical gravity from stars and dark matter dominates in outer disks. We also find that ΣSFR has a strong, nearly linear correlation with Ptot, which itself is within ~13% of the dynamical equilibrium estimate Ptot, DE. The quantitative relationships we find between &SigmaSFR and the turbulent and thermal pressures show that star formation is highly efficient for energy and momentum production, in contrast to the low efficiency of mass consumption. Star formation rates adjust until the ISM's energy and momentum losses are replenished by feedback within a dynamical time.

  5. Model simulation of solute leaching and its application for estimating the net rate of nitrate formation under field conditions

    NASA Astrophysics Data System (ADS)

    Otoma, Suehiro; Kuboi, Toru

    1985-12-01

    A model of the discrete type was built to describe unsteady infiltrations and redistributions of water and solutes in soil. The model was evaluated by comparing the measurements of the changes in chloride concentration in the field soil amended with sewage sludge with those obtained by simulation. The simulations showed that the amount of chloride adsorbed in the field was as small as 60% of that measured in the flask of the batch test, and that most of the chloride leached quickly through the upper zone of soil (0-20 cm) but stagnated in the lower zone (20-100 cm). The model was applied for estimating the daily net rate of nitrate formation. The estimation results indicated that the rate was accelerated remarkably by rainfall and abruptly slowed down soon after.

  6. CARBON-RICH MOLECULAR CHAINS IN PROTOPLANETARY AND PLANETARY ATMOSPHERES: QUANTUM MECHANISMS AND ELECTRON ATTACHMENT RATES FOR ANION FORMATION

    SciTech Connect

    Carelli, F.; Grassi, T.; Gianturco, F. A.; Satta, M.

    2013-09-10

    The elementary mechanisms through which molecular polyynes could form stable negative ions after interacting with free electrons in planetary atmospheres (e.g., Titan's) are analyzed using quantum scattering calculations and quantum structure methods. The case of radical species and of nonpolar partners are analyzed via specific examples for both the C{sub n}H and HC{sub n}H series, with n values from 4 to 12. We show that attachment processes to polar radicals are dominating the anionic production and that the mediating role of dipolar scattering states is crucial to their formation. The corresponding attachment rates are presented as calculated upper limits to their likely values and are obtained down to the low temperatures of interest. The effects of the computed rates, when used in simple evolutionary models, are also investigated and presented in detail.

  7. Fiber Bragg grating based notch filter for bit-rate-transparent NRZ to PRZ format conversion with two-degree-of-freedom optimization

    NASA Astrophysics Data System (ADS)

    Cao, Hui; Shu, Xuewen; Atai, Javid; Zuo, Jun; Xiong, Bangyun; Shen, Fangcheng; Liu, xin; Cheng, Jianqun

    2015-02-01

    We propose a novel notch-filtering scheme for bit-rate transparent all-optical NRZ-to-PRZ format conversion. The scheme is based on a two-degree-of-freedom optimally designed fiber Bragg grating. It is shown that a notch filter optimized for any specific operating bit rate can be used to realize high-Q-factor format conversion over a wide bit rate range without requiring any tuning.

  8. Using Uranium-Series Isotopes to Quantify Volcanic Soil Formation Rates Under a Tropical Climate: Basse-Terre, Guadeloupe

    NASA Astrophysics Data System (ADS)

    Pereyra, Y.; Ma, L.; Sak, P. B.; Gaillardet, J.; Buss, H. L.; Brantley, S. L.

    2014-12-01

    U-series isotopes fractionate during chemical weathering and their activity ratios have been used to determine timescales and rates of soil formation. Such soil formation rates are measured at soil profile scale and provide an important link to compare chemical weathering rates measured across different spatial scales. We analyzed U-series isotope compositions in a ~12m deep soil profile in Basse-Terre Island of French Guadeloupe. The tropical Bras David watershed is developed on andesitic pyroclastic flows. Field observations have shown heterogeneity in color and texture in this profile. However, major element chemistry and mineralogy show some general depth trends. First, Al, Fe, and Ti show a depletion profile relative to Th from 12m to 4m depth, an addition from 4m to 2m, and depletion from 2m to the surface. Second, mobile elements such as Ca, Mg, and Sr have undergone intensive weathering, therefore show almost complete depletion even in the deep profile, and an addition profile near the surface. This addition trend is most likely related to atmospheric dust and marine aerosol signatures. Finally, K, Mn, and Si show a partial depletion profile at depth. The main minerals present throughout the soil profile are halloysite and gibbsite. 238U/232Th ratios in this profile ranged from 0.374 to 1.696, while the 230Th/232Th ratios ranged from 0.367 to 1.701. A decrease of (238U/232Th) in the deep soil profile from 12m to 4m depth is observed, and an increase in the shallow profile from 4m to the surface. The (230Th /232Th) ratios showed a similar trend as (238U/232Th). Marine aerosols and atmospheric dust are responsible for the addition of U in shallow soils while intensive chemical weathering is responsible for the loss of U at depth. U-series chemical weathering model suggests that the weathering duration from 12m to 4m depth is about 250kyr, with a weathering advancing rate of ~30 m/Ma. The rate is also about one order of magnitude lower than the weathering rate

  9. Local structure formation in alkyl-imidazolium-based ionic liquids as revealed by linear and nonlinear Raman spectroscopy.

    PubMed

    Iwata, Koichi; Okajima, Hajime; Saha, Satyen; Hamaguchi, Hiro-O

    2007-11-01

    We show several pieces of Raman spectroscopic evidence that are indicative of local structure formation in imidazolium-based ionic liquids. Low-frequency Raman spectra of C n mimX, where C n mim stands for 1-alkyl(C n H 2 n+1 )-3-methylimidazolium cation and X represents the anion, exhibit broad bands assignable to collective modes of local structures. Spatial distributions of coherent anti-Stokes Raman scattering (CARS) signals from C n mim[PF 6] are consistent with local structures whose size increases with increasing n. Picosecond Raman spectra of S 1 trans-stilbene as a "picosecond Raman thermometer" show microscopic thermal inhomogeneity ascribable to local structure formation in C 2mimTf 2N and C 4mimTf 2N. We also describe two novel phenomena that we believe are relevant to extraordinary nanoenvironments generated by local structures in a magnetic ionic liquid C 4mim[FeCl 4]. PMID:17963358

  10. A Developmental Framework for Complex Plasmodesmata Formation Revealed by Large-Scale Imaging of the Arabidopsis Leaf Epidermis[W

    PubMed Central

    Fitzgibbon, Jessica; Beck, Martina; Zhou, Ji; Faulkner, Christine; Robatzek, Silke; Oparka, Karl

    2013-01-01

    Plasmodesmata (PD) form tubular connections that function as intercellular communication channels. They are essential for transporting nutrients and for coordinating development. During cytokinesis, simple PDs are inserted into the developing cell plate, while during wall extension, more complex (branched) forms of PD are laid down. We show that complex PDs are derived from existing simple PDs in a pattern that is accelerated when leaves undergo the sink–source transition. Complex PDs are inserted initially at the three-way junctions between epidermal cells but develop most rapidly in the anisocytic complexes around stomata. For a quantitative analysis of complex PD formation, we established a high-throughput imaging platform and constructed PDQUANT, a custom algorithm that detected cell boundaries and PD numbers in different wall faces. For anticlinal walls, the number of complex PDs increased with increasing cell size, while for periclinal walls, the number of PDs decreased. Complex PD insertion was accelerated by up to threefold in response to salicylic acid treatment and challenges with mannitol. In a single 30-min run, we could derive data for up to 11k PDs from 3k epidermal cells. This facile approach opens the door to a large-scale analysis of the endogenous and exogenous factors that influence PD formation. PMID:23371949

  11. The Human SepSecS-tRNA[superscript Sec] Complex Reveals the Mechanism of Selenocysteine Formation

    SciTech Connect

    Palioura, Sotiria; Sherrer, R. Lynn; Steitz, Thomas A.; Söll, Dieter; Simonovic, Miljan

    2009-08-13

    Selenocysteine is the only genetically encoded amino acid in humans whose biosynthesis occurs on its cognate transfer RNA (tRNA). O-Phosphoseryl-tRNA:selenocysteinyl-tRNA synthase (SepSecS) catalyzes the final step of selenocysteine formation by a poorly understood tRNA-dependent mechanism. The crystal structure of human tRNA{sup Sec} in complex with SepSecS, phosphoserine, and thiophosphate, together with in vivo and in vitro enzyme assays, supports a pyridoxal phosphate-dependent mechanism of Sec-tRNA{sup Sec} formation. Two tRNA{sup Sec} molecules, with a fold distinct from other canonical tRNAs, bind to each SepSecS tetramer through their 13-base pair acceptor-T{Upsilon}C arm (where {Upsilon} indicates pseudouridine). The tRNA binding is likely to induce a conformational change in the enzyme's active site that allows a phosphoserine covalently attached to tRNA{sup Sec}, but not free phosphoserine, to be oriented properly for the reaction to occur.

  12. Sequence Comparisons of Odorant Receptors among Tortricid Moths Reveal Different Rates of Molecular Evolution among Family Members

    PubMed Central

    Carraher, Colm; Authier, Astrid; Steinwender, Bernd; Newcomb, Richard D.

    2012-01-01

    In insects, odorant receptors detect volatile cues involved in behaviours such as mate recognition, food location and oviposition. We have investigated the evolution of three odorant receptors from five species within the moth genera Ctenopseustis and Planotrotrix, family Tortricidae, which fall into distinct clades within the odorant receptor multigene family. One receptor is the orthologue of the co-receptor Or83b, now known as Orco (OR2), and encodes the obligate ion channel subunit of the receptor complex. In comparison, the other two receptors, OR1 and OR3, are ligand-binding receptor subunits, activated by volatile compounds produced by plants - methyl salicylate and citral, respectively. Rates of sequence evolution at non-synonymous sites were significantly higher in OR1 compared with OR2 and OR3. Within the dataset OR1 contains 109 variable amino acid positions that are distributed evenly across the entire protein including transmembrane helices, loop regions and termini, while OR2 and OR3 contain 18 and 16 variable sites, respectively. OR2 shows a high level of amino acid conservation as expected due to its essential role in odour detection; however we found unexpected differences in the rate of evolution between two ligand-binding odorant receptors, OR1 and OR3. OR3 shows high sequence conservation suggestive of a conserved role in odour reception, whereas the higher rate of evolution observed in OR1, particularly at non-synonymous sites, may be suggestive of relaxed constraint, perhaps associated with the loss of an ancestral role in sex pheromone reception. PMID:22701634

  13. Using U-series isotopes to quantify regolith formation and chemical weathering rates along a climosequence associated with the Susquehanna Shale Hills Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Ma, L.; Chabaux, F. J.; Dere, A. L.; White, T.; Jin, L.; Brantley, S. L.

    2012-12-01

    (sun-facing) slope are characterized by faster regolith production rates (~40-52 m/Myr) and shorter durations of chemical weathering in the regolith zone (~12-16 kyr). These results reveal the important control of hill-slope aspect on the rate of regolith formation at Shale Hills: we hypothesize that aspect creates microclimates that in turn affect slope stability and erosion, and set different regolith residence times. The difference in microclimate is inferred to have been important before and during the periglacial period that occurred at Shale Hills ~15 ka. Our ongoing investigation of the four additional gray shale watersheds in VA, TN, AL, and PR provides information on shale weathering along a climosequence at a much larger continental scale. Only ridge top sites were selected to limit the aspect effect. This systematic study will enable us to quantitatively model regolith formation and landscape development on gray shales and to consider the effects of ongoing climate change.

  14. Providing Stringent Star Formation Rate Limits of z ∼ 2 QSO Host Galaxies at High Angular Resolution

    NASA Astrophysics Data System (ADS)

    Vayner, Andrey; Wright, Shelley A.; Do, Tuan; Larkin, James E.; Armus, Lee; Gallagher, S. C.

    2016-04-01

    We present integral field spectrograph (IFS) with laser guide star adaptive optics (LGS-AO) observations of z ∼ 2 quasi-stellar objects (QSOs) designed to resolve extended nebular line emission from the host galaxy. Our data was obtained with W. M. Keck and Gemini North Observatories, using OSIRIS and NIFS coupled with the LGS-AO systems, respectively. We have conducted a pilot survey of five QSOs, three observed with NIFS+AO and two observed with OSIRIS+AO at an average redshift of z = 2.2. We demonstrate that the combination of AO and IFSs provides the necessary spatial and spectral resolutions required to separate QSO emission from its host. We present our technique for generating a point-spread function (PSF) from the broad-line region of the QSO and performing PSF subtraction of the QSO emission to detect the host galaxy emission at a separation of ∼0.″2 (∼1.4 kpc). We detect Hα narrow-line emission for two sources, SDSS J1029+6510 (zHα = 2.182) and SDSS J0925+0655 (zHα = 2.197), that have evidence for both star formation and extended narrow-line emission. Assuming that the majority of narrow-line Hα emission is from star formation, we infer a star formation rate (SFR) for SDSS J1029+6510 of 78.4 M⊙ yr‑1 originating from a compact region that is kinematically offset by 290–350 km s‑1. For SDSS J0925+0655 we infer a SFR of 29 M⊙ yr‑1 distributed over three clumps that are spatially offset by ∼7 kpc. The null detections on three of the QSOs are used to infer surface brightness limits and we find that at 1.4 kpc from the QSO the un-reddened star formation limit is ≲0.3 M⊙ yr‑1 kpc‑2. If we assume typical extinction values for z = 2 type-1 QSOs, the dereddened SFR for our null detections would be ≲0.6 M⊙ yr‑1 kpc‑2. These IFS observations indicate that while the central black hole is accreting mass at 10%–40% of the Eddington rate, if star formation is present in the host (1.4–20 kpc) it would have to occur diffusely

  15. Artificial Recharge Rates in Granites, Basalt, Sedimentary and Alluvial Formations of Andhra Pradesh, India, Using Injection Tritium Tracer

    NASA Astrophysics Data System (ADS)

    Rangarajan, R.; Muralidharan, D.; Hodlur, G. K.; Banerjee, Pallavi

    2010-05-01

    Rate of groundwater artificial recharge is a very unpredictable and complex phenomenon to understand. But it is a vital parameter to be known for groundwater budgeting and management. Percolation of a portion of the rainfall through the vadoze zone is the principal source of regional artificial recharge to the aquifer system. Tritium injection method based on the piston flow model is ideally suitable for quantifying the downward flux of moisture in the vadoes zone and for the measuring the artificial recharge rate under various hydrogeological conditions. Recharge rates due to monsoon rainfall were measured using injected tritium tracer technique in 17 watersheds / basins located in granite, basalt, sedimentary and alluvium formations of Andhra Pradesh during the last two and half decades. Recharge measurement were made at several sites in each watershed or basin area. At each site, tritiated water was injected at the depth of 60 cm below ground level before the onset of monsoon and vertical soil core profiles in 10 cm section were collected after the completion of monsoon. After laboratory process to measure the moisture content and tritium concentration, the recharge values are computed. The recharge rate measurements facilitate to demarcate favorable areas for taking up artificial recharge measures.

  16. Simulating the formation of massive seed black holes in the early Universe - II. Impact of rate coefficient uncertainties

    NASA Astrophysics Data System (ADS)

    Glover, Simon C. O.

    2015-11-01

    We investigate how uncertainties in the chemical and cooling rate coefficients relevant for a metal-free gas influence our ability to determine the critical ultraviolet field strength required to suppress H2 cooling in high-redshift atomic cooling haloes. The suppression of H2 cooling is a necessary prerequisite for the gas to undergo direct collapse and form an intermediate mass black hole. These black holes can then act as seeds for the growth of the supermassive black holes (SMBHs) observed at redshifts z ˜ 6. The viability of this model for SMBH formation depends on the critical ultraviolet field strength, Jcrit: if this is too large, then too few seeds will form to explain the observed number density of SMBHs. We show in this paper that there are five key chemical reactions whose rate coefficients are uncertain enough to significantly affect Jcrit. The most important of these is the collisional ionization of hydrogen by collisions with other hydrogen atoms, as the rate for this process is very poorly constrained at the low energies relevant for direct collapse. The total uncertainty introduced into Jcrit by this and the other four reactions could in the worst case approach a factor of five. We also show that the use of outdated or inappropriate values for the rates of some chemical reactions in previous studies of the direct collapse mechanism may have significantly affected the values of Jcrit determined by these studies.

  17. Sill intrusion driven fluid flow and vent formation in volcanic basins: Modeling rates of volatile release and paleoclimate effects

    NASA Astrophysics Data System (ADS)

    Iyer, Karthik; Schmid, Daniel

    2016-04-01

    Evidence of mass extinction events in conjunction with climate change occur throughout the geological record and may be accompanied by pronounced negative carbon isotope excursions. The processes that trigger such globally destructive changes are still under considerable debate. These include mechanisms such as poisoning from trace metals released during large volcanic eruptions (Vogt, 1972), CO2 released from lava degassing during the formation of Large Igneous Provinces (LIPs) (Courtillot and Renne, 2003) and CH4 release during the destabilization of sub-seafloor methane (Dickens et al., 1995), to name a few. Thermogenic methane derived from contact metamorphism associated with magma emplacement and cooling in sedimentary basins has been recently gaining considerable attention as a potential mechanism that may have triggered global climate events in the past (e.g. Svensen and Jamtveit, 2010). The discovery of hydrothermal vent complexes that are spatially associated with such basins also supports the discharge of greenhouse gases into the atmosphere (e.g. Jamtveit et al., 2004; Planke et al., 2005; Svensen et al., 2006). A previous study that investigated this process using a fluid flow model (Iyer et al., 2013) suggested that although hydrothermal plume formation resulting from sill emplacement may indeed release large quantities of methane at the surface, the rate at which this methane is released into the atmosphere is too slow to trigger, by itself, some of the negative δ13C excursions observed in the fossil record over short time scales observed in the fossil record. Here, we reinvestigate the rates of gas release during sill emplacement in a case study from the Harstad Basin off-shore Norway with a special emphasis on vent formation. The presented study is based on a seismic line that crosses multiple sill structures emplaced around 55 Ma within the Lower Cretaceous sediments. A single well-defined vent complex is interpreted above the termination of the

  18. Reconstruction of the ancestral plastid genome in Geraniaceae reveals a correlation between genome rearrangements, repeats, and nucleotide substitution rates.

    PubMed

    Weng, Mao-Lun; Blazier, John C; Govindu, Madhumita; Jansen, Robert K

    2014-03-01

    Geraniaceae plastid genomes are highly rearranged, and each of the four genera already sequenced in the family has a distinct genome organization. This study reports plastid genome sequences of six additional species, Francoa sonchifolia, Melianthus villosus, and Viviania marifolia from Geraniales, and Pelargonium alternans, California macrophylla, and Hypseocharis bilobata from Geraniaceae. These genome sequences, combined with previously published species, provide sufficient taxon sampling to reconstruct the ancestral plastid genome organization of Geraniaceae and the rearrangements unique to each genus. The ancestral plastid genome of Geraniaceae has a 4 kb inversion and a reduced, Pelargonium-like small single copy region. Our ancestral genome reconstruction suggests that a few minor rearrangements occurred in the stem branch of Geraniaceae followed by independent rearrangements in each genus. The genomic comparison demonstrates that a series of inverted repeat boundary shifts and inversions played a major role in shaping genome organization in the family. The distribution of repeats is strongly associated with breakpoints in the rearranged genomes, and the proportion and the number of large repeats (>20 bp and >60 bp) are significantly correlated with the degree of genome rearrangements. Increases in the degree of plastid genome rearrangements are correlated with the acceleration in nonsynonymous substitution rates (dN) but not with synonymous substitution rates (dS). Possible mechanisms that might contribute to this correlation, including DNA repair system and selection, are discussed. PMID:24336877

  19. Decadal trends reveal recent acceleration in the rate of recovery from acidification in the northeastern U.S.

    PubMed

    Strock, Kristin E; Nelson, Sarah J; Kahl, Jeffrey S; Saros, Jasmine E; McDowell, William H

    2014-05-01

    Previous reports suggest variable trends in recovery from acidification in northeastern U.S. surface waters in response to the Clean Air Act Amendments. Here we analyze recent trends in emissions, wet deposition, and lake chemistry using long-term data from a variety of lakes in the Adirondack Mountains and New England. Sulfate concentration in wet deposition declined by more than 40% in the 2000s and sulfate concentration in lakes declined at a greater rate from 2002 to 2010 than during the 1980s or 1990s (-3.27 μeq L(-1)year(-1) as compared to -1.26 μeq L(-1)year(-1)). During the 2000s, nitrate concentration in wet deposition declined by more than 50% and nitrate concentration in lakes, which had no linear trend prior to 2000, declined at a rate of -0.05 μeq L(-1)year(-1). Base cation concentrations, which decreased during the 1990s (-1.5 μeq L(-1) year(-1)), have stabilized in New England lakes. Although total aluminum concentrations increased since 1999 (2.57 μg L(-1) year(-1)), there was a shift to nontoxic, organic aluminum. Despite this recent acceleration in recovery in multiple variables, both ANC and pH continue to have variable trends. This may be due in part to variable trajectories in the concentrations of base cations and dissolved organic carbon among our study lakes. PMID:24669928

  20. Heavy water and (15) N labelling with NanoSIMS analysis reveals growth rate-dependent metabolic heterogeneity in chemostats.

    PubMed

    Kopf, Sebastian H; McGlynn, Shawn E; Green-Saxena, Abigail; Guan, Yunbin; Newman, Dianne K; Orphan, Victoria J

    2015-07-01

    To measure single-cell microbial activity and substrate utilization patterns in environmental systems, we employ a new technique using stable isotope labelling of microbial populations with heavy water (a passive tracer) and (15) N ammonium in combination with multi-isotope imaging mass spectrometry. We demonstrate simultaneous NanoSIMS analysis of hydrogen, carbon and nitrogen at high spatial and mass resolution, and report calibration data linking single-cell isotopic compositions to the corresponding bulk isotopic equivalents for Pseudomonas aeruginosa and Staphylococcus aureus. Our results show that heavy water is capable of quantifying in situ single-cell microbial activities ranging from generational time scales of minutes to years, with only light isotopic incorporation (∼0.1 atom % (2) H). Applying this approach to study the rates of fatty acid biosynthesis by single cells of S. aureus growing at different rates in chemostat culture (∼6 h, 1 day and 2 week generation times), we observe the greatest anabolic activity diversity in the slowest growing populations. By using heavy water to constrain cellular growth activity, we can further infer the relative contributions of ammonium versus amino acid assimilation to the cellular nitrogen pool. The approach described here can be applied to disentangle individual cell activities even in nutritionally complex environments. PMID:25655651

  1. Heavy water and 15N labeling with NanoSIMS analysis reveals growth-rate dependent metabolic heterogeneity in chemostats

    PubMed Central

    McGlynn, Shawn E.; Green-Saxena, Abigail

    2015-01-01

    To measure single cell microbial activity and substrate utilization patterns in environmental systems, we employ a new technique using stable isotope labeling of microbial populations with heavy water (a passive tracer) and 15N ammonium in combination with multi-isotope imaging mass spectrometry. We demonstrate simultaneous NanoSIMS analysis of hydrogen, carbon and nitrogen at high spatial and mass resolution, and report calibration data linking single cell isotopic compositions to the corresponding bulk isotopic equivalents for Pseudomonas aeruginosa and Staphylococcus aureus. Our results show that heavy water is capable of quantifying in situ single cell microbial activities ranging from generational time scales of minutes to years, with only light isotopic incorporation (∼0.1 atom % 2H). Applying this approach to study the rates of fatty acid biosynthesis by single cells of S. aureus growing at different rates in chemostat culture (∼6 hours, 1 day and 2 week generation times), we observe the greatest anabolic activity diversity in the slowest growing populations. By using heavy water to constrain cellular growth activity, we can further infer the relative contributions of ammonium vs. amino acid assimilation to the cellular nitrogen pool. The approach described here can be applied to disentangle individual cell activities even in nutritionally complex environments. PMID:25655651

  2. Comparison of Subantarctic Mode Water and Antarctic Intermediate Water formation rates in the South Pacific between NCAR-CCSM4 and observations

    SciTech Connect

    Hartin, Corinne A.; Fine, Rana A.; Kamenkovich, Igor; Sloyan, Bernadette M.

    2014-01-28

    Average formation rates for Subantarctic Mode (SAMW) and Antarctic Intermediate Waters (AAIW) in the South Pacific are calculated from the National Center for Atmospheric Research Community Climate System Model version 4 (NCAR-CCSM4), using chlorofluorocarbon inventories. CFC-12 inventories and formation rates are compared to ocean observations. CCSM4 accurately simulates the southeast Pacific as the main formation region for SAMW and AAIW. CCSM4 formation rates for SAMW are 3.4 Sv, about half of the observational rate. Shallow mixed layers and a thinner SAMW in CCSM4 are responsible for lower formation rates. A formation rate of 8.1 Sv for AAIW in CCSM4 is higher than observations. Higher inventories in CCSM4 in the southwest and central Pacific, and higher surface concentrations are the main reasons for higher formation rates of AAIW. This comparison of model and observations is useful for understanding the uptake and transport of other gases, e.g., CO2 by the model.

  3. Limits on the star formation rates of z>2 damped Lyα systems from Hα spectroscopy

    NASA Astrophysics Data System (ADS)

    Bunker, Andrew J.; Warren, Stephen J.; Clements, D. L.; Williger, Gerard M.; Hewett, Paul C.

    1999-11-01

    We present the results of a long-slit K-band spectroscopic search for Hα emission from eight damped Lyα absorbers (DLAs) at z>2 with the goal of measuring the star formation rates in these systems. For each system we searched for compact sources of Hα emission within a solid angle 11x2.5arcsec2 (44x10h-2kpc2, for q0=0.5, H0=100hkms-1Mpc-1). No Hα emission was detected above 3σ limits in the range (6.5-16)x10-20Wm-2, equivalent to star formation rates of 5.6-18h-2Msolaryr-1, for a standard initial mass function, assuming the lines are spectrally unresolved (<650kms-1 FWHM). We compare these results against the predictions of the models of Pei & Fall of the global history of star formation, under two different simplifying hypotheses: (i) the space density of DLAs at z=2.3 is equal to the space density of spiral galaxies today (implying DLA discs were larger in the past, the `large-disc' hypothesis); (ii) the sizes of DLAs at z=2.3 were the same as the gas sizes of spiral galaxies today (implying DLA discs were more common in the past, the `hierarchical' hypothesis). Compared with the previous most sensitive spectroscopic search, our sample is twice as large, our limits are a factor greater than two deeper, and the solid angle surveyed is over three times as great. Despite this, our results are not in conflict with either the large-disc hypothesis, because of the limited solid angle covered by the slit, or the hierarchical hypothesis, because of the limited sensitivity.

  4. Fast formation of aerobic granules by combining strong hydraulic selection pressure with overstressed organic loading rate.

    PubMed

    Liu, Yong-Qiang; Tay, Joo-Hwa

    2015-09-01

    The combined strong hydraulic selection pressure (HSP) with overstressed organic loading rate (OLR) as a fast granulation strategy was used to enhance aerobic granulation. To investigate the wide applicability of this strategy to different scenarios and its relevant mechanism, different settling times, different inoculums, different exchange ratios, different reactor configurations, and different shear force were used in this study. It was found that clear granules were formed within 24 h and steady state reached within three days when the fast granulation strategy was used in a lab-scale reactor seeded with well settled activated sludge (Reactor 2). However, granules appeared after 2-week operation and reached steady state after one month at the traditional step-wise decreased settling time from 20 to 2 min with OLR of 6 g COD/L·d (Reactor 1). With the fast granulation strategy, granules appeared within 24 h even with bulking sludge as seed to start up Reactor 3, but 6-day lag phase was observed compared with Reactor 2. Both Reactor 2 and Reactor 3 experienced sigmoidal growth curve in terms of biomass accumulation and granule size increase after granulation. In addition, the reproducible results in pilot-scale reactors (Reactor 5 and Reactor 6) with diameter of 20 cm and height/diameter ratio (H/D) of 4 further proved that reactor configuration and fluid flow pattern had no effect on the aerobic granulation when the fast granulation strategy was employed, but biomass accumulation experienced a short lag phase too in Reactor 5 and Reactor 6. Although overstressed OLR was favorable for fast granulation, it also led to the fluffy granules after around two-week operation. However, the stable 6-month operation of Reactor 3 demonstrated that the rapidly formed granules were able to maintain long-term stability by reducing OLR from 12 g COD/L·d to 6 g COD/L·d. A mechanism of fast granulation with the strategy of combined strong HSP and OLR was proposed to explain

  5. The three-dimensional folding of the α-globin gene domain reveals formation of chromatin globules.

    PubMed

    Baù, Davide; Sanyal, Amartya; Lajoie, Bryan R; Capriotti, Emidio; Byron, Meg; Lawrence, Jeanne B; Dekker, Job; Marti-Renom, Marc A

    2011-01-01

    We developed a general approach that combines chromosome conformation capture carbon copy (5C) with the Integrated Modeling Platform (IMP) to generate high-resolution three-dimensional models of chromatin at the megabase scale. We applied this approach to the ENm008 domain on human chromosome 16, containing the α-globin locus, which is expressed in K562 cells and silenced in lymphoblastoid cells (GM12878). The models accurately reproduce the known looping interactions between the α-globin genes and their distal regulatory elements. Further, we find using our approach that the domain folds into a single globular conformation in GM12878 cells, whereas two globules are formed in K562 cells. The central cores of these globules are enriched for transcribed genes, whereas nontranscribed chromatin is more peripheral. We propose that globule formation represents a higher-order folding state related to clustering of transcribed genes around shared transcription machineries, as previously observed by microscopy. PMID:21131981

  6. Prolonged Mantle Melting Revealed in the Curaçao Lava Formation: Implications for the Origin of the Caribbean Plateau

    NASA Astrophysics Data System (ADS)

    Krawl, K.; Duncan, R. A.; Kent, A. J.; Loewen, M.

    2013-12-01

    The Curaçao Lava Formation (CLF), a ~5 km thick section of submarine-erupted lava flows, hyaloclastites, dikes and sills, provides a ~30 Ma record of the magmatic processes involved in the formation of the Caribbean Large Igneous Province (CLIP). The CLF presents ol-tholeiitic and picritic compositions, exposed along the southern transform margin of the CLIP, that are typical of other in situ and tectonized pieces of this ocean plateau. The wide range of recently acquired 40Ar-39Ar ages (62 to 93 Ma) obtained for the Curaçao lavas contradicts previous proposals that the CLF formed over a relatively short period (1-2 million years), but is similar to extended volcanic histories recorded in Haiti (Dumisseau Fm) and at the Beata Ridge. Petrochemical modeling using MELTS indicates that the CLF rock compositions could have formed by fractional crystallization of high-MgO parental magmas with broadly similar major element contents, generated during multiple melting events over this prolonged period. The persistently flat rare earth element patterns in rocks spanning the full age range of the CLF can be reproduced by 10-30% partial melting of a predominantly depleted mantle source with a minor enriched component. The geochemical and age data and modeling results are consistent with a mantle dynamic model for the CLIP in which lateral displacement of mantle plume head material beneath the Caribbean plateau results from subduction-driven mantle flow, which allows for the generation of magmas from a continuously replenished mantle source over approximately 30 million years. While no subduction influence is seen in CLF compositions, the island does record intrusive, arc-related rocks.

  7. High Acidification Rate of Norwegian Sea Revealed by Boron Isotopes in the Deep-Sea Coral Madrepora Oculata

    NASA Astrophysics Data System (ADS)

    Gonzalez, C.; Douville, E.; Hall-Spencer, J.; Montagna, P.; Louvat, P.; Gaillardet, J.; Frank, N.; Bordier, L.; Juillet-Leclerc, A.

    2012-12-01

    Ocean acidification and global warming due to the increase of anthropogenic CO2 are major threats for marine calcifying organisms, such as deep-sea corals, particularly in high-latitude regions. In order to evaluate the current anthropogenic perturbation and to properly assess the impacts and responses of calcifiers to previous changes in pH it is critical to investigate past changes of the seawater carbonate system. Unfortunately, current instrumental records of oceanic pH are limited, covering only a few decades. Scleractinian coral skeletons record chemical parameters of the seawater in which they grow. However, pH variability over multidecadal timescales remains largely unknown in intermediate and deep seawater masses. Here we present a study that highlights the potential of deep-sea-corals to overcome the lack of long-term pH records and that emphasizes a rapid acidification of high latitude subsurface waters of Norwegian Sea during the past decades. We have reconstructed seawater pH and temperature from a well dated deep-sea coral specimen Madrepora oculata collected alive from Røst reef in Norwegian Sea (67°N, 9°E, 340 m depth). This large branching framework forming coral species grew its skeleton over more than four decades determined using AMS 14C and 210Pb dating (Sabatier et al. 2012). B-isotopes and Li/Mg ratios yield an acidification rate of about -0.0030±0.0008 pH-unit.year-1 and a warming of 0.3°C during the past four decades (1967-2007). Overall our reconstruction technique agrees well with previous pH calculations (Hönisch et al., 2007 vs. Trotter et al., 2011 and McCulloch et al., 2012, i.e. the iterative method), but additional corrections are here applied using stable isotope correlations (O, C, B) to properly address kinetic fractionation of boron isotopes used for pH reconstruction. The resulting pH curve strongly anti-correlates with the annual NAO index, which further strengthens our evidence for the ocean acidification rate

  8. Galaxy pairs in the Sloan Digital Sky Survey - X. Does gas content alter star formation rate enhancement in galaxy interactions?

    NASA Astrophysics Data System (ADS)

    Scudder, Jillian M.; Ellison, Sara L.; Momjian, Emmanuel; Rosenberg, Jessica L.; Torrey, Paul; Patton, David R.; Fertig, Derek; Mendel, J. Trevor

    2015-06-01

    New spectral line observations, obtained with the Jansky Very Large Array (VLA), of a sample of 34 galaxies in 17 close pairs are presented in this paper. The sample of galaxy pairs is selected to contain galaxies in close, major interactions (i.e. projected separations <30 h_{70}^{-1} kpc, and mass ratios less extreme than 4:1), while still having a sufficiently large angular separation that the VLA can spatially resolve both galaxies in the pair. Of the 34 galaxies, 17 are detected at >3σ. We compare the H I gas fraction of the galaxies with the triggered star formation present in that galaxy. When compared to the star formation rates (SFRs) of non-pair galaxies matched in mass, redshift, and local environment, we find that the star formation enhancement is weakly positively correlated (˜2.5σ) with H I gas fraction. In order to help understand the physical mechanisms driving this weak correlation, we also present results from a small suite of binary galaxy merger simulations with varying gas fractions. The simulated galaxies indicate that larger initial gas fractions are associated with lower levels of interaction-triggered star formation (relative to an identical galaxy in isolation), but also show that high gas fraction galaxies have higher absolute SFRs prior to an interaction. We show that when interaction-driven SFR enhancements are calculated relative to a galaxy with an average gas fraction for its stellar mass, the relationship between SFR and initial gas fraction dominates over the SFR enhancements driven by the interaction. Simulated galaxy interactions that are matched in stellar mass but not in gas fraction, like our VLA sample, yield the same general positive correlation between SFR enhancement and gas fraction that we observe.

  9. Mathematical modeling reveals the functional implications of the different nuclear shuttling rates of Erk1 and Erk2

    NASA Astrophysics Data System (ADS)

    Harrington, Heather A.; Komorowski, Michał; Beguerisse-Díaz, Mariano; Ratto, Gian Michele; Stumpf, Michael P. H.

    2012-06-01

    The mitogen-activated protein kinase (MAPK) family of proteins is involved in regulating cellular fates such as proliferation, differentiation and apoptosis. In particular, the dynamics of the Erk/Mek system, which has become the canonical example for MAPK signaling systems, have attracted considerable attention. Erk is encoded by two genes, Erk1 and Erk2, that until recently had been considered equivalent as they differ only subtly at the sequence level. However, these proteins exhibit radically different trafficking between cytoplasm and nucleus and this fact may have functional implications. Here we use spatially resolved data on Erk1/2 to develop and analyze spatio-temporal models of these cascades, and we discuss how sensitivity analysis can be used to discriminate between mechanisms. Our models elucidate some of the factors governing the interplay between signaling processes and the Erk1/2 localization in different cellular compartments, including competition between Erk1 and Erk2. Our approach is applicable to a wide range of signaling systems, such as activation cascades, where translocation of molecules occurs. Our study provides a first model of Erk1 and Erk2 activation and their nuclear shuttling dynamics, revealing a role in the regulation of the efficiency of nuclear signaling.

  10. Quantitative TCR:pMHC Dissociation Rate Assessment by NTAmers Reveals Antimelanoma T Cell Repertoires Enriched for High Functional Competence.

    PubMed

    Gannon, Philippe O; Wieckowski, Sébastien; Baumgaertner, Petra; Hebeisen, Michaël; Allard, Mathilde; Speiser, Daniel E; Rufer, Nathalie

    2015-07-01

    Experimental models demonstrated that therapeutic induction of CD8 T cell responses may offer protection against tumors or infectious diseases providing that T cells have sufficiently high TCR/CD8:pMHC avidity for efficient Ag recognition and consequently strong immune functions. However, comprehensive characterization of TCR/CD8:pMHC avidity in clinically relevant situations has remained elusive. In this study, using the novel NTA-His tag-containing multimer technology, we quantified the TCR:pMHC dissociation rates (koff) of tumor-specific vaccine-induced CD8 T cell clones (n = 139) derived from seven melanoma patients vaccinated with IFA, CpG, and the native/EAA or analog/ELA Melan-A(MART-1)(26-35) peptide, binding with low or high affinity to MHC, respectively. We observed substantial correlations between koff and Ca(2+) mobilization (p = 0.016) and target cell recognition (p < 0.0001), with the latter independently of the T cell differentiation state. Our strategy was successful in demonstrating that the type of peptide impacted on TCR/CD8:pMHC avidity, as tumor-reactive T cell clones derived from patients vaccinated with the low-affinity (native) peptide expressed slower koff rates than those derived from patients vaccinated with the high-affinity (analog) peptide (p < 0.0001). Furthermore, we observed that the low-affinity peptide promoted the selective differentiation of tumor-specific T cells bearing TCRs with high TCR/CD8:pMHC avidity (p < 0.0001). Altogether, TCR:pMHC interaction kinetics correlated strongly with T cell functions. Our study demonstrates the feasibility and usefulness of TCR/CD8:pMHC avidity assessment by NTA-His tag-containing multimers of naturally occurring polyclonal T cell responses, which represents a strong asset for the development of immunotherapy. PMID:26002978

  11. Effect of repulsive interactions on the rate of doublet formation of colloidal nanoparticles in the presence of convective transport.

    PubMed

    Lattuada, Marco; Morbidelli, Massimo

    2011-03-01

    In this work, we have performed a systematic investigation of the effect of electrostatic repulsive interactions on the aggregation rate of colloidal nanoparticles to from doublets in the presence of a convective transport mechanism. The aggregation rate has been computed by solving numerically the Fuchs-Smoluchowski diffusion-convection equation. Two convective transport mechanisms have been considered: extensional flow field and gravity-induced relative sedimentation. A broad range of conditions commonly encountered in the applications of colloidal dispersions has been analyzed. The relative importance of convective to diffusive contributions has been quantified by using the Peclet number Pe. The simulation results indicate that, in the presence of repulsive interactions, the evolution of the aggregation rate as a function of Pe can always be divided into three distinct regimes, no matter which convective mechanism is considered. At low Pe values the rate of aggregation is independent of convection and is dominated by repulsive interactions. At high Pe values, the rate of aggregation is dominated by convection, and independent of repulsive interactions. At intermediate Pe values, a sharp transition between these two regimes occurs. During this transition, which occurs usually over a 10-100-fold increase in Pe values, the aggregation rate can change by several orders of magnitude. The interval of Pe values where this transition occurs depends upon the nature of the convective transport mechanism, as well as on the height and characteristic lengthscale of the repulsive barrier. A simplified model has been proposed that is capable of quantitatively accounting for the simulations results. The obtained results reveal unexpected features of the effect of ionic strength and particle size on the stability of colloidal suspensions under shear or sedimentation, which have relevant consequences in industrial applications. PMID:21193203

  12. Decoupled crystallization and eruption histories of the rhyolite magmatic system at Tarawera volcano revealed by zircon ages and growth rates

    NASA Astrophysics Data System (ADS)

    Storm, Sonja; Shane, Phil; Schmitt, Axel K.; Lindsay, Jan M.

    2012-03-01

    We obtained U-Th disequilibrium age data on zircons from each of the four rhyolite eruptions that built Tarawera volcano in the last 22 ka within the Okataina Volcanic Center (OVC), caldera, New Zealand. Secondary ion mass spectrometry analyses on unpolished euhedral crystal faces that lack resorption features show that crystal growth variously terminated from near-eruption age to ~100 ka prior to eruption. Age-depth profiling of crystals reveals long periods of continuous (~34 ka) and discontinuous growth (~90 ka). Growth hiatuses of up to ~40 ka duration occur, but do not all relate to obvious resorption surfaces. Age differences up to similar magnitude are found on opposing faces of some crystals suggesting episodes of partial exposure to melts. These features are best explained by periodic, complete, or partial, sub-solidus storage and/or inclusion in larger crystal phases, followed by rapid liberation prior to eruption. This is supported by high abundances of U and Th (~500 - >2,000 ppm) in some zircons consistent with periods of high crystallinity (>70%) in the magmatic system, based on crystal/melt partitioning. Contemporaneous but contrasting rim-ward trends of these elements within crystals, even in the same lava hand sample, require synchronous growth in separate melt bodies and little connectivity within the system, but also significant crystal transport and mixing prior to eruption. Many crystals record continuity of growth through the preceding ~60 ka OVC caldera-collapse and subsequent eruptions from Tarawera. This demonstrates a decoupling between eruption triggers, such as shallow crustal extension and mafic intrusion, and the crystallization state of the OVC silicic magmatic system. The data highlights the need to distinguish between the time for accumulation of eruptible magma and the long-term magma residence time based on the age of crystals with high closure temperatures, when assessing the potential for catastrophic eruptions.

  13. Lactose uptake rate measurements by 14C-labelled lactose reveals promotional activity of porous cellulose in whey fermentation by kefir yeast.

    PubMed

    Golfinopoulos, Aristidis; Soupioni, Magdalini; Kopsahelis, Nikolaos; Tsaousi, Konstantina; Koutinas, Athanasios A

    2012-10-15

    Lactose uptake rate by kefir yeast, immobilized on tubular cellulose and gluten pellets during fermentation of lactose and whey, was monitored using (14)C-labelled lactose. Results illustrated that, in all cases, lactose uptake rate was strongly correlated with fermentation rate and the fermentation's kinetic parameters were improved by kefir yeast entrapped in tubular cellulose. As a result, twofold faster fermentations were achieved in comparison with kefir yeast immobilized on gluten. This is probably due to cluster and hydrogen bonds formation between cellulose and inhibitors, such as Ca(++) and generated lactic acid, by which they leave the liquid medium. The findings, regarding the promotional effect of cellulose, seem promising for application in industrial whey fermentations. PMID:23442646

  14. Galaxies undergoing ram-pressure stripping: the influence of the bulge on morphology and star formation rate

    NASA Astrophysics Data System (ADS)

    Steinhauser, D.; Haider, M.; Kapferer, W.; Schindler, S.

    2012-08-01

    Aims: We investigate the influence of stellar bulges on the star formation and morphology of disc galaxies that suffer from ram pressure. Several tree-SPH (smoothed particle hydrodynamics) simulations have been carried out to study the dependence of the star formation rate on the mass and size of a stellar bulge. In addition, different strengths of ram pressure and different alignments of the disc with respect to the intra-cluster medium (ICM) are applied. Methods: The simulations were carried out with the combined N-body/hydrodynamic code GADGET-2 with radiative cooling and a recipe for star formation. The same galaxy with different bulge sizes was used to accomplish 31 simulations with varying inclination angles and surrounding gas densities of 10-27g cm-3 and 10-28g cm-3. For all the simulations a relative velocity of 1000 km s-1 for the galaxies and an initial gas temperature for the ICM of 107K were applied. Besides galaxies flying edge-on and face-on through the surrounding gas, various disc tilt angles in between were used. To allow a comparison, the galaxies with the different bulges were also evolved in isolation to contrast the star formation rates. Furthermore, the influence of different disc gas mass fractions has been investigated. Results: As claimed in previous works, when ram pressure is acting on a galaxy, the star formation rate (SFR) is enhanced and rises up to four times with increasing ICM density compared to galaxies that evolve in isolation. However, a bulge suppresses the SFR when the same ram pressure is applied. Consequently, fewer new stars are formed because the SFR can be lowered by up to 2M⊙ yr-1. Furthermore, the denser the surrounding gas, the more interstellar medium (ISM) is stripped. While at an ICM density of 10-28g cm-3 about 30% of the ISM is stripped, the galaxy is almost completely (more than 90%) stripped when an ICM density of 10-27g cm-3 is applied. But again, a bulge prevents the stripping of the ISM and reduces the

  15. What does the fine-scale petrography of IDPs reveal about grain formation and evolution in the early solar system?

    NASA Technical Reports Server (NTRS)

    Bradley, John

    1994-01-01

    The 'pyroxene' interplanetary dust particles (IDP's) may be the best samples for investigation of primordial grain-forming reactions because they appear to have experienced negligible post-accretional alteration. They are likely to continue to yield information about gas-to-solid condensation and other grain-forming reactions that may have occurred either in the solar nebular or presolar interstellar environments. An immediate challenge lies in understanding the nanometer-scale petrography of the ultrafine-grained aggregates in 'pyroxene' IDP's. Whether these aggregates contain components from diverse grain-forming environments may ultimately be answered by systematic petrographic studies using electron microscopes capable of high spatial resolution microanalysis. It may be more difficult to decipher evidence of grain formation and evolution in 'olivine' and 'layer silicate' IDP's because they appear to have experienced post-accretional alteration. Most of the studied 'olivine' IDPs have been subjected to heating and equilibration, perhaps during atmospheric entry, while the 'layer silicate' IDP's have experienced aqueous alteration.

  16. Genomewide analysis of the Drosophila tetraspanins reveals a subset with similar function in the formation of the embryonic synapse

    PubMed Central

    Fradkin, Lee G.; Kamphorst, Jessica T.; DiAntonio, Aaron; Goodman, Corey S.; Noordermeer, Jasprina N.

    2002-01-01

    Tetraspanins encode a large conserved family of proteins that span the membrane four times and are expressed in a variety of eukaryotic tissues. They are part of membrane complexes that are involved in such diverse processes as intracellular signaling, cellular motility, metastasis, and tumor suppression. The single fly tetraspanin characterized to date, late bloomer (lbm), is expressed on the axons, terminal arbors, and growth cones of motoneurons. In embryos lacking Lbm protein, motoneurons reach their muscle targets, but initially fail to form synaptic terminals. During larval stages, however, functional contacts are formed. The newly available genomic sequence of Drosophila melanogaster indicates the existence of 34 additional members of the tetraspanin family in the fly. To address the possibility that other tetraspanins with functions that might compensate for a lack of lbm exist, we determined the expression domains of the Drosophila tetraspanin gene family members by RNA in situ analysis. We found two other tetraspanins also expressed in motoneurons and subsequently generated a small chromosomal deletion that removes all three motoneuron-specific tetraspanins. The deletion results in a significant enhancement in the lbm phenotype, indicating that the two additional motoneuron-expressed tetraspanins can, at least in part, compensate for the absence of lbm during the formation of the embryonic synapse. PMID:12370414

  17. Before the flood: Miocene otoliths from eastern Amazon Pirabas Formation reveal a Caribbean-type fish fauna

    NASA Astrophysics Data System (ADS)

    Aguilera, Orangel; Schwarzhans, Werner; Moraes-Santos, Heloísa; Nepomuceno, Aguinaldo

    2014-12-01

    The Pirabas Formation of Early Miocene age represents the final stage of the central western Atlantic carbonate platform in northeastern South America, predating the emplacement of the Amazon delta system. The otolith-based fossil fish fauna is represented by 38 species typical of a shallow marine environment. A total of 18 species are described new to science from the families Congridae, Batrachoididae, Bythitidae, Sciaenidae and Paralichthyidae. The fish fauna was associated with high benthic and planktic primary productivity including seagrass meadows, calcareous algae and suspension-feeders. The break of todays shallow marine bioprovince at the Amazonas delta mouth is not evident from the fish fauna of the Pirabas Fm., which shows good correlation with the Gatunian/proto-Caribbean bioprovince known from an only slightly younger time window in Trinidad and Venezuela. Differences observed to those Early Miocene faunal associations are interpreted to be mainly due to stratigraphic and geographic and not environmental differences. We postulate that the emergence of the Amazonas river mouth close to its present day location has terminated the carbonate cycle of the Pirabas Fm. and pushed back northwards a certain proportion of the fish fauna here described.

  18. Conditional knockdown of BCL2A1 reveals rate-limiting roles in BCR-dependent B-cell survival.

    PubMed

    Sochalska, M; Ottina, E; Tuzlak, S; Herzog, S; Herold, M; Villunger, A

    2016-04-01

    Bcl2 family proteins control mitochondrial apoptosis and its members exert critical cell type and differentiation stage-specific functions, acting as barriers against autoimmunity or transformation. Anti-apoptotic Bcl2a1/Bfl1/A1 is frequently deregulated in different types of blood cancers in humans but its physiological role is poorly understood as quadruplication of the Bcl2a1 gene locus in mice hampers conventional gene targeting strategies. Transgenic overexpression of A1, deletion of the A1-a paralogue or constitutive knockdown in the hematopoietic compartment of mice by RNAi suggested rate-limiting roles in lymphocyte development, granulopoiesis and mast cell activation. Here we report on the consequences of conditional knockdown of A1 protein expression using a reverse transactivator (rtTA)-driven approach that highlights a critical role for this Bcl2 family member in the maintenance of mature B-cell homeostasis. Furthermore, we define the A1/Bim (Bcl-2 interacting mediator of cell death) axis as a target of key kinases mediating B-cell receptor (BCR)-dependent survival signals, such as, spleen tyrosine kinase (Syk) and Brutons tyrosine kinase (Btk). As such, A1 represents a putative target for the treatment of B-cell-related pathologies depending on hyperactivation of BCR-emanating survival signals and loss of A1 expression accounts, in part, for the pro-apoptotic effects of Syk- or Btk inhibitors that rely on the 'BH3-only' protein Bim for cell killing. PMID:26450454

  19. Effect of internal cavities on folding rates and routes revealed by real-time pressure-jump NMR spectroscopy.

    PubMed

    Roche, Julien; Dellarole, Mariano; Caro, José A; Norberto, Douglas R; Garcia, Angel E; Garcia-Moreno, Bertrand; Roumestand, Christian; Royer, Catherine A

    2013-10-01

    The time required to fold proteins usually increases significantly under conditions of high pressure. Taking advantage of this general property of proteins, we combined P-jump experiments with NMR spectroscopy to examine in detail the folding reaction of staphylococcal nuclease (SNase) and of some of its cavity-containing variants. The nearly 100 observables that could be measured simultaneously collectively describe the kinetics of folding as a function of pressure and denaturant concentration with exquisite site-specific resolution. SNase variants with cavities in the central core of the protein exhibit a highly heterogeneous transition-state ensemble (TSE) with a smaller solvent-excluded void volume than the TSE of the parent SNase. This heterogeneous TSE experiences Hammond behavior, becoming more native-like (higher molar volume) with increasing denaturant concentration. In contrast, the TSE of the L125A variant, which has a cavity at the secondary core, is only slightly different from that of the parent SNase. Because pressure acts mainly to eliminate solvent-excluded voids, which are heterogeneously distributed throughout structures, it perturbs the protein more selectively than chemical denaturants, thereby facilitating the characterization of intermediates and the consequences of packing on folding mechanisms. Besides demonstrating how internal cavities can affect the routes and rates of folding of a protein, this study illustrates how the combination of P-jump and NMR spectroscopy can yield detailed mechanistic insight into protein folding reactions with exquisite site-specific temporal information. PMID:23987660

  20. The Phase Space of z=1.2 Clusters: Probing Dust Temperature and Star Formation Rate as a Function of Environment and Accretion History

    NASA Astrophysics Data System (ADS)

    Noble, Allison; SpARCS Collaboration

    2016-01-01

    Understanding the influence of environment is a fundamental goal in studies of galaxy formation and evolution, and galaxy clusters offer ideal laboratories with which to examine environmental effects on their constituent members. Clusters continually evolve and build up mass through the accumulation of galaxies and groups, resulting in distinct galaxy populations based on their accretion history. In Noble et al. 2013, we presented a novel definition for environment using the phase space of line-of-sight velocity and clustercentric radius, which probes the time-averaged density to which a galaxy has been exposed and traces out accretion histories. Using this dynamical definition of environment reveals a decline in specific star formation towards the cluster core in the earliest accreted galaxies, and was further shown to isolate post-starburst galaxies within clusters (Muzzin et al. 2014). We have now extended this work to higher-redshift clusters at z=1.2 using deep Herschel-PACS and -SPIRE data. With a sample of 120 spectroscopically-confirmed cluster members, we investigate various galaxy properties as a function of phase-space environment. Specifically, we use 5-band Herschel photometry to estimate the dust temperature and star formation rate for dynamically distinct galaxy populations, namely recent infalls and those that were accreted into the cluster at an earlier epoch (Noble et al. submitted). These properties are then compared to a field sample of star-forming galaxies at 1.1 < z < 1.2 to shed light on cluster-specific processes in galaxy evolution. In this talk I will discuss the various implications of a phase-space definition for environment, and present our most recent results, focusing on how this accretion-based definition aids our understanding of quenching mechanisms within z=1.2 galaxies.

  1. Structural reconstruction and spontaneous formation of Fe polynuclears: a self-assembly of Fe-porphyrin coordination chains on Au(111) revealed by scanning tunneling microscopy.

    PubMed

    Wang, Yuxu; Zhou, Kun; Shi, Ziliang; Ma, Yu-Qiang

    2016-06-01

    A self-assembled Fe-porphyrin coordination chain structure on a Au(111) surface is investigated by scanning tunneling microscopy (STM), revealing structural reconstruction resulting from an alternative change of molecular orientations and spontaneous formation of uniformly sized Fe polynuclears. The alternation of the molecular orientations is ascribed to the cooperation of the attractive coordination and the intermolecular steric repulsion as elucidated by high-resolution STM observations. Furthermore, chemical control experiments are carried out to determine the number of atoms in an Fe polynuclear, suggesting a tentative Fe dinuclear-module that serves not only as a coordination center to link porphyrin units together but also as a "dangling" site for further functionalization by a guest terpyridine ligand. The chain structure and the Fe polynuclears are stable up to 320 K as revealed by real-time STM scanning. Annealing at higher temperatures converts the chain structure into a two-dimensional coordination structure. PMID:27167835

  2. Spatially resolved physical conditions of molecular gas and potential star formation