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. 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.

  8. 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.

  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. 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.

  9. 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.

  10. 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.

  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. 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.

  16. 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.

  17. 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.

  18. 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).

  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. 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.…

  10. 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...

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  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

    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

  3. 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.

  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. 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

  9. 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

  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 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

  16. 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

  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

    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.

  19. 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

  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. 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...

  6. 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...

  7. 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...

  8. 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...

  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, 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...

  10. 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...

  11. 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

  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. 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

  5. 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

  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. 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.

  20. 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...

  1. 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.

  2. 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"…

  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. 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

  14. [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

  15. 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

  16. 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...

  17. 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...

  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, 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...

  19. 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...

  20. 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

  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. 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

  3. 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

  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. 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

  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. 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

  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. 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.

  17. 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

  18. 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

  19. 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%.

  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.

    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

  3. 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.

  4. 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.

  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. 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

  8. 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

  9. 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.

  10. 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.

  11. 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.

  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. 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

  15. 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

  16. 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

  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. 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

  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.

    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

  20. 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

  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. 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

  5. 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

  6. 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.

  7. 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

  8. 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

  9. 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

  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. 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.

  12. 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.

  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. 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.

  15. 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.

  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.