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  1. The VLT FLAMES Tarantula Survey

    NARCIS (Netherlands)

    Evans, C.; Taylor, W.; Sana, H.; Hénault-Brunet, V.; Bagnoli, T.; Bastian, N.; Bestenlehner, J.; Bonanos, A.; Bressert, E.; Brott, I.; Campbell, M.; Cantiello, M.; Carraro, G.; Clark, S.; Costa, E.; Crowther, P.; de Koter, A.; de Mink, S.; Doran, E.; Dufton, P.; Dunstall, P.; Garcia, M.; Gieles, M.; Gräfener, G.; Herrero, A.; Howarth, I.; Izzard, R.; Köhler, K.; Langer, N.; Lennon, D.; Maíz Apellániz, J.; Markova, N.; Najarro, P.; Puls, J.; Ramirez, O.; Sabín-Sanjulián, C.; Simón-Díaz, S.; Smartt, S.; Stroud, V.; van Loon, J.; Vink, J.S.; Walborn, N.

    2011-01-01

    We introduce the VLT FLAMES Tarantula Survey, an ESO Large Programme from which we have obtained optical spectroscopy of over 800 massive stars in the spectacular 30 Doradus region of the Large Magellanic Cloud. A key feature is the use of multi-epoch observations to provide strong constraints on

  2. The VLT-FLAMES Tarantula survey

    NARCIS (Netherlands)

    Taylor, W.D.; Evans, C.J.; Henault-Brunet, V.; Bastian, N.; Beletsky, Y.; Bestenlehner, J.; Brott, I.; Cantiello, M.; Carraro, G.; Clark, J.S.; Crowther, P.A.; de Koter, A.; de Mink, S.E.; Doran, E.; Dufton, P.L.; Dunstall, P.; Gieles, M.; Grafener, G.; Herrero, A.; Howarth, I.D.; Langer, N.; Lennon, D.J.; Maiz-Apellaniz, J; Markova, N.; Najarro, P.; Puls, J.; Sana, H.A.A.; Simon-Diaz, S.; Smartt, S.J.; Stroud, V.E.; van Loon, J.T.; Vink, J.S.; Walborn, N.R.

    2011-01-01

    The VLT-FLAMES Tarantula Survey is an ESO Large Programme that has provided multi-epoch spectroscopy of over 1000 stars in the 30 Doradus region in the Large Magellanic Cloud. Armed with this unique dataset the assembled consortium is now addressing a broad range of fundamental questions in both ste

  3. The VLT-FLAMES Tarantula survey

    NARCIS (Netherlands)

    Markova, N.; Evans, C.J.; Bastian, N.; Beletsky, Y.; Bestenlehner, J.; Brott, I.; Cantiello, M.; Carraro, G.; Clark, J.S.; Crowther, P.A.; de Koter, A.; de Mink, S.E.; Doran, E.; Dufton, P.L.; Dunstall, P.; Gieles, M.; Graefener, G.; Henault-Brunet, V.; Herrero, A.; Howarth, I.D.; Langer, N.; Lennon, D.J.; Maiz-Appellaniz, J.; Najarro, F.; Puls, J.; Sana, H.A.A.; Simon-Diaz, S.; Smartts, S.J.; Stroud, V.E.; Taylor, W.D.; van Loon, J.T.; Vink, J.S.; Walborn, N.R.

    2011-01-01

    The Tarantula survey is an ESO Large Programme which has obtained multi- epochs spectroscopy of over 800 massive stars in the 30 Dor region in the Large Magelanic Cloud. Here we briefly describe the main drivers of the survey and the observational material derived.

  4. The VLT-FLAMES Tarantula Survey

    NARCIS (Netherlands)

    Evans, C.J.; Bastian, N.; Beletsky, Y.; Brott, I.; Cantiello, M.; Clark, J.S.; Crowther, P.A.; de Koter, A.; de Mink, S.E.; Dufton, P.L.; Dunstall, P.; Gieles, M.; Gräfener, G.; Hénault-Brunet, V.; Herrero, A.; Howarth, I.D.; Langer, N.; Lennon, D.J.; Maíz Apellániz, J.; Markova, N.; Najarro, F.; Puls, J.; Sana, H.; Simón-Díaz, S.; Smartt, S.J.; Stroud, V.E.; Taylor, W.D.; Trundle, C.; van Loon, J.T.; Vink, J.S.; Walborn, N.R.

    2010-01-01

    The Tarantula Survey is an ambitious ESO Large Programme that has obtained multi-epoch spectroscopy of over 1000 massive stars in the 30 Doradus region in the Large Magellanic Cloud. Here, we introduce the scientific motivations of the survey and give an overview of the observational sample.

  5. The VLT-FLAMES Tarantula survey

    NARCIS (Netherlands)

    Markova, N.; Evans, C.J.; Bastian, N.; Beletsky, Y.; Bestenlehner, J.; Brott, I.; Cantiello, M.; Carraro, G.; Clark, J.S.; Crowther, P.A.; de Koter, A.; de Mink, S.E.; Doran, E.; Dufton, P.L.; Dunstall, P.; Gieles, M.; Graefener, G.; Henault-Brunet, V.; Herrero, A.; Howarth, I.D.; Langer, N.; Lennon, D.J.; Maiz-Appellaniz, J.; Najarro, F.; Puls, J.; Sana, H.A.A.; Simon-Diaz, S.; Smartts, S.J.; Stroud, V.E.; Taylor, W.D.; van Loon, J.T.; Vink, J.S.; Walborn, N.R.

    2011-01-01

    The Tarantula survey is an ESO Large Programme which has obtained multi- epochs spectroscopy of over 800 massive stars in the 30 Dor region in the Large Magelanic Cloud. Here we briefly describe the main drivers of the survey and the observational material derived.

  6. The VLT-FLAMES Tarantula Survey

    CERN Document Server

    Evans, C J; Beletsky, Y; Brott, I; Cantiello, M; Clark, J S; Crowther, P A; De Koter, A; de Mink, S; Dufton, P L; Dunstall, P; Gieles, M; Graefener, G; Henault-Brunet, V; Herrero, A; Howarth, I D; Langer, N; Lennon, D J; Apellaniz, J Maiz; Markova, N; Najarro, F; Puls, J; Sana, H; Simon-Diaz, S; Smartt, S J; Stroud, V E; Taylor, W D; Trundle, C; van Loon, J Th; Vink, J S; Walborn, N R

    2009-01-01

    The Tarantula Survey is an ambitious ESO Large Programme that has obtained multi-epoch spectroscopy of over 1,000 massive stars in the 30 Doradus region of the Large Magellanic Cloud. Here we introduce the scientific motivations of the survey and give an overview of the observational sample. Ultimately, quantitative analysis of every star, paying particular attention to the effects of rotational mixing and binarity, will be used to address fundamental questions in both stellar and cluster evolution.

  7. The VLT-FLAMES Tarantula Survey: I. Introduction and observational overview

    NARCIS (Netherlands)

    Evans, C.J.; Taylor, W.D.; Hénault-Brunet, V.; Sana, H.A.A.; de Koter, A.; Simón-Díaz, S.; Carraro, G.; Bagnoli, T.; Bastian, N.; Bestenlehner, J.M.; Bonanos, A.Z.; Bressert, E.; Brott, I.; Campbell, M.A.; Cantiello, M.; Clark, J.S.; Costa, E.; Crowther, P.A.; de Mink, S.E.; Doran, E.; Dufton, P.L.; Dunstall, P.R.; Friedrich, K.; Garcia, M.; Gieles, M.; Gräfener, G.; Herrero, A.; Howarth, I.D.; Izzard, R.G.; Langer, N.; Lennon, D.J.; Maiz Apellániz, J.; Markova, N.; Najarro, F.; Puls, J.; Ramirez, O.H.; Sabín-Sanjulián, C.; Smartt, S.J.; Stroud, V.E.; van Loon, J.T.; Vink, J.S.; Walborn, N.R.

    2011-01-01

    The VLT-FLAMES Tarantula Survey (VFTS) is an ESO Large Programme that has obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). Here we introduce our scientific motivations and give an overview of the survey targets, includi

  8. The VLT-FLAMES Tarantula Survey. I. Introduction and observational overview

    NARCIS (Netherlands)

    Evans, C.J.; Taylor, W.D.; de Koter, A.; Brott, I.; Walborn, N.R.

    2011-01-01

    The VLT-FLAMES Tarantula Survey (VFTS) is an ESO Large Programme that has obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). Here we introduce our scientific motivations and give an overview of the survey targets, includi

  9. The VLT-FLAMES Tarantula Survey. XXII. Multiplicity properties of the B-type stars

    NARCIS (Netherlands)

    Dunstall, P.R.; Dufton, P.L.; Sana, H.; Evans, C.J.; Howarth, I.D.; Simón-Díaz, S.; de Mink, S.E.; Langer, N.; Maíz Apellániz, J.; Taylor, W.D.

    2015-01-01

    We investigate the multiplicity properties of 408 B-type stars observed in the 30 Doradus region of the Large Magellanic Cloud with multi-epoch spectroscopy from the VLT-FLAMES Tarantula Survey (VFTS). We use a cross-correlation method to estimate relative radial velocities from the helium and metal

  10. VizieR Online Data Catalog: O-stars in VLT-FLAMES Tarantula Survey (Ramirez-Agudelo+ 2013)

    Science.gov (United States)

    Ramirez-Agudelo, O. H.; Simon-Diaz, S.; Sana, H.; de Koter, A.; Sabin-Sanjulian, C.; de Mink, S. E.; Dufton, P. L.; Grafener, G.; Evans, C. J.; Herrero, A.; Langer, N.; Lennon, D. J.; Maiz Apellaniz, J.; Markova, N.; Najarro, F.; Puls, J.; Vink, J. S.

    2013-09-01

    Projected rotational velocity measurements of 216 O-type stars observed at multi-epochs as part as the VLT-FLAMES Tarantula Survey. We measured projected rotational velocities by means of a Fourier transform method and a profile fitting method applied on a set of isolated spectral lines. (2 data files).

  11. The VLT-FLAMES Tarantula Survey XXI. Stellar spin rates of O-type spectroscopic binaries

    CERN Document Server

    Ramírez-Agudelo, O H; de Mink, S E; Hénault-Brunet, V; de Koter, A; Langer, N; Tramper, F; Gräfener, G; Evans, C J; Vink, J S; Dufton, P L; Taylor, W D

    2015-01-01

    The initial distribution of spin rates of massive stars is a fingerprint of their elusive formation process. It also sets a key initial condition for stellar evolution and is thus an important ingredient in stellar population synthesis. So far, most studies have focused on single stars. Most O stars are however found in multiple systems. By establishing the spin-rate distribution of a sizeable sample of O-type spectroscopic binaries and by comparing the distributions of binary sub-populations with one another as well as with that of presumed single stars in the same region, we aim to constrain the initial spin distribution of O stars in binaries, and to identify signatures of the physical mechanisms that affect the evolution of the massive stars spin rates. We use ground-based optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS) to establish the projected equatorial rotational velocities (\\vrot) for components of 114 spectroscopic binaries in 30 Doradus. The \\vrot\\ values a...

  12. The VLT-FLAMES Tarantula Survey XIV. The O-Type Stellar Content of 30 Doradus

    CERN Document Server

    Walborn, N R; Simon-Diaz, S; Apellaniz, J Maiz; Taylor, W D; Evans, C J; Markova, N; Lennon, D J; de Koter, A

    2014-01-01

    Detailed spectral classifications are presented for 352 O-B0 stars in the VLT-FLAMES Tarantula Survey, of which 213 O-type are of sufficient quality for further morphological analysis. Among them, six subcategories of special interest are distinguished. (1) Several new examples of the earliest spectral types O2-O3 have been found. (2) A group of extremely rapidly rotating main-sequence objects has been isolated, including the largest $v\\sin i$ values known, the spatial and radial-velocity distributions of which suggest ejection from the two principal ionizing clusters. (3) Several new examples of the evolved, rapidly rotating Onfp class show similar evidence. (4) No fewer than 48 members of the Vz category, hypothesized to be on or near the ZAMS, are found in this sample; in contrast to the rapid rotators, they are strongly concentrated to the ionizing clusters, supporting their interpretation as very young objects, as do their relatively faint absolute magnitudes. (5) A surprisingly large fraction of the mai...

  13. The VLT-FLAMES Tarantula Survey XII. Rotational velocities of the single O-type stars

    CERN Document Server

    Ramírez-Agudelo, O H; Sana, H; de Koter, A; Sabín-Sanjulían, C; de Mink, S E; Dufton, P L; Gräfener, G; Evans, C J; Herrero, A; Langer, N; Lennon, D J; Apellániz, J Maíz; Markova, N; Najarro, F; Puls, J; Taylor, W D; Vink, J S

    2013-01-01

    Aims. Using ground based multi-object optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS), we aim to establish the (projected) rotational velocity distribution for a sample of 216 presumably single O-type stars in 30 Doradus (30 Dor). Methods. We measured projected rotational velocities, \\vrot, by means of a Fourier transform method and a profile fitting method applied on a set of isolated spectral lines. We also used an iterative deconvolution procedure to infer the probability density, $\\rm{P(\\veq)}$, of the equatorial rotational velocity, \\veq. Results. The distribution of \\vrot\\ shows a two-component structure: a peak around 80 \\kms\\ and a high-velocity tail extending up to $\\sim$600 \\kms. This structure is also present in the inferred distribution $\\rm{P(\\veq)}$ with around 80% of the sample having 0 $<$ \\veq\\, $\\leq\\, 300$ \\kms\\ and the other 20% distributed in the high-velocity region. Conclusions. Most of the stars in our sample rotate with a rate less than 20%\\...

  14. The VLT-FLAMES Tarantula Survey I: Introduction and observational overview

    CERN Document Server

    Evans, C J; Henault-Brunet, V; Sana, H; de Koter, A; Simon-Diaz, S; Carraro, G; Bagnoli, T; Bastian, N; Bestenlehner, J M; Bonanos, A Z; Bressert, E; Brott, I; Campbell, M A; Cantiello, M; Clark, J S; Costa, E; Crowther, P A; de Mink, S E; Doran, E; Dufton, P L; Dunstall, P R; Friedrich, K; Garcia, M; Gieles, M; Graefener, G; Herrero, A; Howarth, I D; Izzard, R G; Langer, N; Lennon, D J; Apellaniz, J Maiz; Markova, N; Najarro, F; Puls, J; Ramirez, O H; Sabin, C; Smartt, S J; Stroud, V E; van Loon, J Th; Vink, J S; Walborn, N R

    2011-01-01

    The VLT-FLAMES Tarantula Survey (VFTS) is an ESO Large Programme that has obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). Here we introduce our scientific motivations and give an overview of the survey targets, including optical and near-infrared photometry and comprehensive details of the data reduction. One of the principal objectives was to detect massive binary systems via variations in their radial velocities, thus shaping the multi-epoch observing strategy. Spectral classifications are given for the massive emission-line stars observed by the survey, including the discovery of a new Wolf-Rayet star (VFTS 682, classified as WN5h), 2' to the northeast of R136. To illustrate the diversity of objects encompassed by the survey, we investigate the spectral properties of sixteen targets identified by Gruendl & Chu from Spitzer photometry as candidate young stellar objects or stars with notable mid-infrared excesses. Detailed ...

  15. The VLT-FLAMES Tarantula Survey II: R139 revealed as a massive binary system

    CERN Document Server

    Taylor, W D; Sana, H; Walborn, N R; de Mink, S E; Stroud, V E; Alvarez-Candal, A; Barbá, R H; Bestenlehner, J M; Bonanos, A Z; Brott, I; Crowther, P A; de Koter, A; Friedrich, K; Gräfener, G; Hénault-Brunet, V; Herrero, A; Kaper, L; Langer, N; Lennon, D J; Apellániz, J Maíz; Markova, N; Morrell, N; Monaco, L; Vink, J S

    2011-01-01

    We report the discovery that R139 in 30 Doradus is a massive spectroscopic binary system. Multi-epoch optical spectroscopy of R139 was obtained as part of the VLT-FLAMES Tarantula Survey, revealing a double-lined system. The two components are of similar spectral types; the primary exhibits strong C III 4650 emission and is classified as an O6.5 Iafc supergiant, while the secondary is an O6 Iaf supergiant. The radial-velocity variations indicate a highly eccentric orbit with a period of 153.9 days. Photometry obtained with the Faulkes Telescope South shows no evidence for significant variability within an 18 month period. The orbital solution yields lower mass limits for the components of M1sin^3 i = 78 \\pm 8 Msun and M2sin^3 i = 66 \\pm 7 Msun. As R139 appears to be the most massive binary system known to contain two evolved Of supergiants, it will provide an excellent test for atmospheric and evolutionary models.

  16. The VLT-FLAMES Tarantula Survey XXII. Multiplicity properties of the B-type stars

    CERN Document Server

    Dunstall, P R; Sana, H; Evans, C J; Howarth, I D; Simón-Díaz, S; de Mink, S E; Langer, N; Apellániz, J Maíz; Taylor, W D

    2015-01-01

    We investigate the multiplicity properties of 408 B-type stars observed in the 30 Doradus region of the Large Magellanic Cloud with multi-epoch spectroscopy from the VLT-FLAMES Tarantula Survey (VFTS). We use a cross-correlation method to estimate relative radial velocities from the helium and metal absorption lines for each of our targets. Objects with significant radial-velocity variations (and with an amplitude larger than 16 km/s) are classified as spectroscopic binaries. We find an observed spectroscopic binary fraction (defined by periods of 0.1) for the B-type stars, f_B(obs) = 0.25 +/- 0.02, which appears constant across the field of view, except for the two older clusters (Hodge 301 and SL 639). These two clusters have significantly lower fractions of 0.08 +/- 0.08 and 0.10 +/- 0.09, respectively. Using synthetic populations and a model of our observed epochs and their potential biases, we constrain the intrinsic multiplicity properties of the dwarf and giant (i.e. relatively unevolved) B-type stars ...

  17. The VLT-FLAMES Tarantula Survey. VIII. Multiplicity properties of the O-type star population

    Science.gov (United States)

    Sana, H.; de Koter, A.; de Mink, S. E.; Dunstall, P. R.; Evans, C. J.; Hénault-Brunet, V.; Maíz Apellániz, J.; Ramírez-Agudelo, O. H.; Taylor, W. D.; Walborn, N. R.; Clark, J. S.; Crowther, P. A.; Herrero, A.; Gieles, M.; Langer, N.; Lennon, D. J.; Vink, J. S.

    2013-02-01

    Context. The Tarantula Nebula in the Large Magellanic Cloud is our closest view of a starburst region and is the ideal environment to investigate important questions regarding the formation, evolution and final fate of the most massive stars. Aims: We analyze the multiplicity properties of the massive O-type star population observed through multi-epoch spectroscopy in the framework of the VLT-FLAMES Tarantula Survey. With 360 O-type stars, this is the largest homogeneous sample of massive stars analyzed to date. Methods: We use multi-epoch spectroscopy and variability analysis to identify spectroscopic binaries. We also use a Monte-Carlo method to correct for observational biases. By modeling simultaneously the observed binary fraction, the distributions of the amplitudes of the radial velocity variations and the distribution of the time scales of these variations, we constrain the intrinsic current binary fraction and period and mass-ratio distributions. Results: We observe a spectroscopic binary fraction of 0.35 ± 0.03, which corresponds to the fraction of objects displaying statistically significant radial velocity variations with an amplitude of at least 20 km s-1. We compute the intrinsic binary fraction to be 0.51 ± 0.04. We adopt power-laws to describe the intrinsic period and mass-ratio distributions: f(log 10P/d) ~ (log 10P/d)π (with log 10P/d in the range 0.15-3.5) and f(q) ~ qκ with 0.1 ≤ q = M2/M1 ≤ 1.0. The power-law indexes that best reproduce the observed quantities are π = -0.45 ± 0.30 and κ = -1.0 ± 0.4. The period distribution that we obtain thus favours shorter period systems compared to an Öpik law (π = 0). The mass ratio distribution is slightly skewed towards low mass ratio systems but remains incompatible with a random sampling of a classical mass function (κ = -2.35). The binary fraction seems mostly uniform across the field of view and independent of the spectral types and luminosity classes. The binary fraction in the outer

  18. The VLT-FLAMES Tarantula Survey. XII. Rotational velocities of the single O-type stars

    Science.gov (United States)

    Ramírez-Agudelo, O. H.; Simón-Díaz, S.; Sana, H.; de Koter, A.; Sabín-Sanjulían, C.; de Mink, S. E.; Dufton, P. L.; Gräfener, G.; Evans, C. J.; Herrero, A.; Langer, N.; Lennon, D. J.; Maíz Apellániz, J.; Markova, N.; Najarro, F.; Puls, J.; Taylor, W. D.; Vink, J. S.

    2013-12-01

    Context. The 30 Doradus (30 Dor) region of the Large Magellanic Cloud, also known as the Tarantula nebula, is the nearest starburst region. It contains the richest population of massive stars in the Local Group, and it is thus the best possible laboratory to investigate open questions on the formation and evolution of massive stars. Aims: Using ground-based multi-object optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS), we aim to establish the (projected) rotational velocity distribution for a sample of 216 presumably single O-type stars in 30 Dor. The sample is large enough to obtain statistically significant information and to search for variations among subpopulations - in terms of spectral type, luminosity class, and spatial location - in the field of view. Methods: We measured projected rotational velocities, νesini, by means of a Fourier transform method and a profile fitting method applied to a set of isolated spectral lines. We also used an iterative deconvolution procedure to infer the probability density, P(νe), of the equatorial rotational velocity, νe. Results: The distribution of νesini shows a two-component structure: a peak around 80 kms-1 and a high-velocity tail extending up to ~600 kms-1. This structure is also present in the inferred distribution P(νe) with around 80% of the sample having 0 low-velocity peak is consistent with what has been found in other studies for late O- and early B-type stars. Conclusions: Most of the stars in our sample rotate with a rate less than 20% of their break-up velocity. For the bulk of the sample, mass loss in a stellar wind and/or envelope expansion is not efficient enough to significantly spin down these stars within the first few Myr of evolution. If massive-star formation results in stars rotating at birth with a large portion of their break-up velocities, an alternative braking mechanism, possibly magnetic fields, is thus required to explain the present

  19. The VLT-FLAMES Tarantula Survey VI: Evidence for rotation of the young massive cluster R136

    CERN Document Server

    Hénault-Brunet, V; Evans, C J; Sana, H; Bastian, N; Apellániz, J Maíz; Taylor, W D; Markova, N; Bressert, E; de Koter, A; van Loon, J Th

    2012-01-01

    Although it has important ramifications for both the formation of star clusters and their subsequent dynamical evolution, rotation remains a largely unexplored characteristic of young star clusters (few Myr). Using multi-epoch spectroscopic data of the inner regions of 30 Doradus in the Large Magellanic Cloud (LMC) obtained as part of the VLT-FLAMES Tarantula Survey, we search for rotation of the young massive cluster R136. From the radial velocities of 36 apparently single O-type stars within a projected radius of 10 pc from the centre of the cluster, we find evidence, at the 95% confidence level, for rotation of the cluster as a whole. We use a maximum likelihood method to fit simple rotation curves to our data and find a typical rotational velocity of ~3 km/s. When compared to the low velocity dispersion of R136, our result suggests that star clusters may form with at least ~20% of the kinetic energy in rotation.

  20. The VLT-FLAMES Tarantula Survey. XV. VFTS\\,822: a candidate Herbig B[e] star at low metallicity

    CERN Document Server

    Kalari, V M; Dufton, P L; Evans, C J; Dunstall, P R; Sana, H; Clark, J S; Ellerbroek, L; de Koter, A; Lennon, D J; Taylor, W D

    2014-01-01

    We report the discovery of the B[e] star VFTS 822 in the 30 Doradus star-forming region of the Large Magellanic Cloud, classified by optical spectroscopy from the VLT-FLAMES Tarantula Survey and complementary infrared photometry. VFTS 822 is a relatively low-luminosity (log $L$ = 4.04 $\\pm$ 0.25 $L_{\\odot}$) B8[e] star. In this Letter, we evaluate the evolutionary status of VFTS 822 and discuss its candidacy as a Herbig B[e] star. If the object is indeed in the pre-main sequence phase, it would present an exciting opportunity to measure mass accretion rates at low metallicity spectroscopically, to understand the effect of metallicity on accretion rates.

  1. The VLT-FLAMES Tarantula Survey III: A very massive star in apparent isolation from the massive cluster R136

    CERN Document Server

    Bestenlehner, Joachim M; Gräfener, G; Najarro, F; Evans, C J; Bastian, N; Bonanos, A Z; Bressert, E; Crowther, P A; Doran, E; Friedrich, K; Hénault-Brunet, V; Herrero, A; de Koter, A; Langer, N; Lennon, D J; Apellániz, J Maíz; Sana, H; Soszynski, I; Taylor, W D

    2011-01-01

    VFTS 682 is located in an active star-forming region, at a projected distance of 29 pc from the young massive cluster R136 in the Tarantula Nebula of the Large Magellanic Cloud. It was previously reported as a candidate young stellar object, and more recently spectroscopically revealed as a hydrogen-rich Wolf-Rayet (WN5h) star. Our aim is to obtain the stellar properties, such as its intrinsic luminosity, and to investigate the origin of VFTS 682. To this purpose, we model optical spectra from the VLT-FLAMES Tarantula Survey with the non-LTE stellar atmosphere code CMFGEN, as well as the spectral energy distribution from complementary optical and infrared photometry. We find the extinction properties to be highly peculiar (RV ~4.7), and obtain a surprisingly high luminosity log(L/Lsun) = 6.5 \\pm 0.2, corresponding to a present-day mass of ~150Msun. The high effective temperature of 52.2 \\pm 2.5kK might be explained by chemically homogeneous evolution - suggested to be the key process in the path towards long ...

  2. The VLT-FLAMES Tarantula Survey. IX. The interstellar medium seen through Diffuse Interstellar Bands and neutral sodium

    CERN Document Server

    van Loon, Jacco Th; Tatton, Benjamin L; Apellaniz, Jesus Maiz; Crowther, Paul A; de Koter, Alex; Evans, Christopher J; Henault-Brunet, Vincent; Howarth, Ian D; Richter, Philipp; Sana, Hugues; Simon-Diaz, Sergio; Taylor, William; Walborn, Nolan R

    2012-01-01

    The Tarantula Nebula (30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud, seen through gas in the Galactic Disc and Halo. Diffuse Interstellar Bands offer a unique probe of the diffuse, cool-warm gas in these regions. The aim is to use DIBs as diagnostics of the local interstellar conditions, whilst at the same time deriving properties of the yet-unknown carriers. Spectra of over 800 early-type stars from the VLT Flames Tarantula Survey (VFTS) were analysed. Maps were created, separately, for the Galactic and LMC absorption in the DIBs at 4428 and 6614 Ang and - in a smaller region near the central cluster R136 - neutral sodium (Na I D); we also measured the DIBs at 5780 and 5797 Ang. The maps show strong 4428 and 6614 Ang DIBs in the quiescent cloud complex to the south of 30 Dor but weak absorption in the harsher environments to the north (bubbles) and near the OB associations. The Na maps show at least five kinematic components in the LMC and a shell-like structure surrounding R136,...

  3. The VLT-FLAMES Tarantula Survey XVIII. Classifications and radial velocities of the B-type stars

    CERN Document Server

    Evans, C J; Dufton, P L; Howarth, I D; Walborn, N R; Markova, N; Clark, J S; de Mink, S E; de Koter, A; Dunstall, P R; Hénault-Brunet, V; Apellániz, J Maíz; McEvoy, C M; Sana, H; Simón-Díaz, S; Taylor, W D; Vink, J S

    2015-01-01

    We present spectral classifications for 438 B-type stars observed as part of the VLT-FLAMES Tarantula Survey (VFTS) in the 30 Doradus region of the Large Magellanic Cloud. Radial velocities are provided for 307 apparently single stars, and for 99 targets with radial-velocity variations which are consistent with them being spectroscopic binaries. We investigate the spatial distribution of the radial velocities across the 30 Dor region, and use the results to identify candidate runaway stars. Excluding potential runaways and members of two older clusters in the survey region (SL 639 and Hodge 301), we determine a systemic velocity for 30 Dor of 271.6 +/- 12.2 km/s from 273 presumed single stars. Employing a 3-sigma criterion we identify nine candidate runaway stars (2.9% of the single stars with radial-velocity estimates). The projected rotational velocities of the candidate runaways appear to be significantly different to those of the full B-type sample, with a strong preference for either large (>345 km/s) or...

  4. The VLT-FLAMES Tarantula Survey. XIII: On the nature of O Vz stars in 30 Doradus

    CERN Document Server

    Sabín-Sanjulián, C; Herrero, A; Walborn, N R; Puls, J; Apellániz, J Maíz; Evans, C J; Brott, I; de Koter, A; Garcia, M; Markova, N; Najarro, F; Ramírez-Agudelo, O H; Sana, H; Taylor, W D; Vink, J S

    2013-01-01

    AIMS. We test the hypothesis of O Vz stars (characterized by having HeII4686 stronger in absorption than other He lines in their blue-violet spectra) being at a younger evolutionary stage than are normal O-type dwarfs. METHODS. We have performed a quantitative spectroscopic analysis of a sample of 38 O Vz and 46 O V stars, identified by the VLT-FLAMES Tarantula Survey in the 30 Doradus region of the Large Magellanic Cloud (LMC). We obtained the stellar and wind parameters of both samples using the FASTWIND stellar atmosphere code and the IACOB-GBAT grid-based automatic tool. In the framework of a differential study, we compared the physical and evolutionary properties of both samples, regarding Teff, logg, logQ and logL. We also investigated the predictions of the FASTWIND code about the O Vz phenomenon. RESULTS. We find a differential distribution of objects in terms of effective temperature, with O Vz stars dominant at intermediate values. The O Vz stars in 30 Doradus tend to be younger and less luminous, a...

  5. The VLT-FLAMES Tarantula Survey IV: Candidates for isolated high-mass star formation in 30 Doradus

    CERN Document Server

    Bressert, E; Evans, C J; Sana, H; Hénault-Brunet, V; Goodwin, S P; Parker, R J; Gieles, M; Bestenlehner, J M; Vink, J S; Taylor, W D; Crowther, P A; Longmore, S N; Gräfener, G; Apellániz, J Maíz; de Koter, A; Cantiello, M; Kruijssen, J M D

    2012-01-01

    Whether massive stars can occasionally form in relative isolation or if they require a large cluster of lower-mass stars around them is a key test in the differentiation of star formation theories as well as how the initial mass function of stars is sampled. Previous attempts to find O-type stars that formed in isolation were hindered by the possibility that such stars are merely runaways from clusters, i.e., their current isolation does not reflect their birth conditions. We introduce a new method to find O-type stars that are not affected by such a degeneracy. Using the VLT-FLAMES Tarantula Survey and additional high resolution imaging we have identified stars that satisfy the following constraints: 1) they are O-type stars that are not detected to be part of a binary system based on RV time series analysis; 2) they are designated spectral type O7 or earlier ; 3) their velocities are within 1\\sigma of the mean of OB-type stars in the 30 Doradus region, i.e. they are not runaways along our line-of-sight; 4) ...

  6. The VLT-FLAMES Tarantula Survey. VII. A low velocity dispersion for the young massive cluster R136

    CERN Document Server

    Hénault-Brunet, V; Sana, H; Gieles, M; Bastian, N; Apellániz, J Maíz; Markova, N; Taylor, W D; Bressert, E; Crowther, P A; van Loon, J Th

    2012-01-01

    Detailed studies of resolved young massive star clusters are necessary to determine their dynamical state and evaluate the importance of gas expulsion and early cluster evolution. In an effort to gain insight into the dynamical state of the young massive cluster R136 and obtain the first measurement of its velocity dispersion, we analyse multi-epoch spectroscopic data of the inner regions of 30 Doradus in the Large Magellanic Cloud (LMC) obtained as part of the VLT-FLAMES Tarantula Survey. Following a quantitative assessment of the variability, we use the radial velocities of non-variable sources to place an upper limit of 6 km/s on the line-of-sight velocity dispersion of stars within a projected distance of 5 pc from the centre of the cluster. After accounting for the contributions of undetected binaries and measurement errors through Monte Carlo simulations, we conclude that the true velocity dispersion is likely between 4 and 5 km/s given a range of standard assumptions about the binary distribution. This...

  7. The VLT-FLAMES Tarantula Survey XXV. Surface nitrogen abundances of O-type giants and supergiants

    CERN Document Server

    Grin, N J; de Koter, A; Sana, H; Puls, J; Brott, I; Crowther, P A; Dufton, P L; Evans, C J; Graefener, G; Herrero, A; Langer, N; Lennon, D J; van Loon, J Th; Markova, N; de Mink, S E; Najarro, F; Schneider, F R N; Taylor, W D; Tramper, F; Vink, J S; Walborn, W R

    2016-01-01

    Theoretically, rotation-induced chemical mixing in massive stars has far reaching evolutionary consequences, affecting the sequence of morphological phases, lifetimes, nucleosynthesis, and supernova characteristics. Using a sample of 72 presumably single O-type giants to supergiants observed in the context of the VLT-FLAMES Tarantula Survey (VFTS), we aim to investigate rotational mixing in evolved core-hydrogen burning stars initially more massive than $15\\,M_\\odot$ by analysing their surface nitrogen abundances. Using stellar and wind properties derived in a previous VFTS study, we constrained the nitrogen abundance by fitting the equivalent widths of relatively strong lines that are sensitive to changes in the abundance of this element. Given the quality of the data, we constrained the nitrogen abundance in 38 cases; for 34 stars only upper limits could be derived, which includes almost all stars rotating at $v_\\mathrm{e}\\sin i >200\\,\\mathrm{km s^{-1}}$. We analysed the nitrogen abundance as a function of ...

  8. The VLT-FLAMES Tarantula Survey X: Evidence for a bimodal distribution of rotational velocities for the single early B-type stars

    CERN Document Server

    Dufton, P L; Dunstall, P R; Evans, C J; Brott, I; de Mink, S E; Howarth, I D; Kennedy, M; McEvoy, C; Potter, A T; Ramírez-Agudelo, O H; Sana, H; Simón-Díaz, S; Taylor, W; Vink, J S

    2012-01-01

    Aims: Projected rotational velocities (\\vsini) have been estimated for 334 targets in the VLT-FLAMES Tarantula survey that do not manifest significant radial velocity variations and are not supergiants. They have spectral types from approximately O9.5 to B3. The estimates have been analysed to infer the underlying rotational velocity distribution, which is critical for understanding the evolution of massive stars. Methods: Projected rotational velocities were deduced from the Fourier transforms of spectral lines, with upper limits also being obtained from profile fitting. For the narrower lined stars, metal and non-diffuse helium lines were adopted, and for the broader lined stars, both non-diffuse and diffuse helium lines; the estimates obtained using the different sets of lines are in good agreement. The uncertainty in the mean estimates is typically 4% for most targets. The iterative deconvolution procedure of Lucy has been used to deduce the probability density distribution of the rotational velocities. R...

  9. The VLT-FLAMES Tarantula Survey. XXV. Surface nitrogen abundances of O-type giants and supergiants

    Science.gov (United States)

    Grin, N. J.; Ramírez-Agudelo, O. H.; de Koter, A.; Sana, H.; Puls, J.; Brott, I.; Crowther, P. A.; Dufton, P. L.; Evans, C. J.; Gräfener, G.; Herrero, A.; Langer, N.; Lennon, D. J.; van Loon, J. Th.; Markova, N.; de Mink, S. E.; Najarro, F.; Schneider, F. R. N.; Taylor, W. D.; Tramper, F.; Vink, J. S.; Walborn, N. R.

    2017-04-01

    Context. Theoretically, rotation-induced chemical mixing in massive stars has far reaching evolutionary consequences, affecting the sequence of morphological phases, lifetimes, nucleosynthesis, and supernova characteristics. Aims: Using a sample of 72 presumably single O-type giants to supergiants observed in the context of the VLT-FLAMES Tarantula Survey (VFTS), we aim to investigate rotational mixing in evolved core-hydrogen burning stars initially more massive than 15 M⊙ by analysing their surface nitrogen abundances. Methods: Using stellar and wind properties derived in a previous VFTS study we computed synthetic spectra for a set of up to 21 N ii-v lines in the optical spectral range, using the non-LTE atmosphere code FASTWIND. We constrained the nitrogen abundance by fitting the equivalent widths of relatively strong lines that are sensitive to changes in the abundance of this element. Given the quality of the data, we constrained the nitrogen abundance in 38 cases; for 34 stars only upper limits could be derived, which includes almost all stars rotating at νesini> 200 km s-1. Results: We analysed the nitrogen abundance as a function of projected rotation rate νesini and confronted it with predictions of rotational mixing. We found a group of N-enhanced slowly-spinning stars that is not in accordance with predictions of rotational mixing in single stars. Among O-type stars with (rotation-corrected) gravities less than log gc = 3.75 this group constitutes 30-40 percent of the population. We found a correlation between nitrogen and helium abundance which is consistent with expectations, suggesting that, whatever the mechanism that brings N to the surface, it displays CNO-processed material. For the rapidly-spinning O-type stars we can only provide upper limits on the nitrogen abundance, which are not in violation with theoretical expectations. Hence, the data cannot be used to test the physics of rotation induced mixing in the regime of high spin rates

  10. The VLT-FLAMES Tarantula Survey . XXIV. Stellar properties of the O-type giants and supergiants in 30 Doradus

    Science.gov (United States)

    Ramírez-Agudelo, O. H.; Sana, H.; de Koter, A.; Tramper, F.; Grin, N. J.; Schneider, F. R. N.; Langer, N.; Puls, J.; Markova, N.; Bestenlehner, J. M.; Castro, N.; Crowther, P. A.; Evans, C. J.; García, M.; Gräfener, G.; Herrero, A.; van Kempen, B.; Lennon, D. J.; Maíz Apellániz, J.; Najarro, F.; Sabín-Sanjulián, C.; Simón-Díaz, S.; Taylor, W. D.; Vink, J. S.

    2017-04-01

    Context. The Tarantula region in the Large Magellanic Cloud (LMC) contains the richest population of spatially resolved massive O-type stars known so far. This unmatched sample offers an opportunity to test models describing their main-sequence evolution and mass-loss properties. Aims: Using ground-based optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS), we aim to determine stellar, photospheric and wind properties of 72 presumably single O-type giants, bright giants and supergiants and to confront them with predictions of stellar evolution and of line-driven mass-loss theories. Methods: We apply an automated method for quantitative spectroscopic analysis of O stars combining the non-LTE stellar atmosphere model fastwind with the genetic fitting algorithm pikaia to determine the following stellar properties: effective temperature, surface gravity, mass-loss rate, helium abundance, and projected rotational velocity. The latter has been constrained without taking into account the contribution from macro-turbulent motions to the line broadening. Results: We present empirical effective temperature versus spectral subtype calibrations at LMC-metallicity for giants and supergiants. The calibration for giants shows a +1kK offset compared to similar Galactic calibrations; a shift of the same magnitude has been reported for dwarfs. The supergiant calibrations, though only based on a handful of stars, do not seem to indicate such an offset. The presence of a strong upturn at spectral type O3 and earlier can also not be confirmed by our data. In the spectroscopic and classical Hertzsprung-Russell diagrams, our sample O stars are found to occupy the region predicted to be the core hydrogen-burning phase by state-of-the-art models. For stars initially more massive than approximately 60 M⊙, the giant phase already appears relatively early on in the evolution; the supergiant phase develops later. Bright giants, however, are not

  11. The VLT-FLAMES Tarantula Survey XVII. Physical and wind properties of massive stars at the top of the main sequence

    CERN Document Server

    Bestenlehner, Joachim M; Vink, Jorick S; Najarro, F; de Koter, A; Sana, H; Evans, C J; Crowther, P A; Hénault-Brunet, V; Herrero, A; Langer, N; Schneider, F R N; Simón-Díaz, S; Taylor, W D; Walborn, N R

    2014-01-01

    The evolution and fate of very massive stars (VMS) is tightly connected to their mass-loss properties. Their initial and final masses differ significantly as a result of mass loss. VMS have strong stellar winds and extremely high ionising fluxes, which are thought to be critical sources of both mechanical and radiative feedback in giant Hii regions. However, how VMS mass-loss properties change during stellar evolution is poorly understood. In the framework of the VLT-Flames Tarantula Survey (VFTS), we explore the mass-loss transition region from optically thin O to denser WNh star winds, thereby testing theoretical predictions. To this purpose we select 62 O, Of, Of/WN, and WNh stars, an unprecedented sample of stars with the highest masses and luminosities known. We perform a spectral analysis of optical VFTS as well as near-infrared VLT/SINFONI data using the non-LTE radiative transfer code CMFGEN to obtain stellar and wind parameters. For the first time, we observationally resolve the transition between op...

  12. The VLT-FLAMES Tarantula Survey XVI. The optical+NIR extinction laws in 30 Doradus and the photometric determination of the effective temperatures of OB stars

    CERN Document Server

    Apellániz, J Maíz; Barbá, R H; Gräfener, G; Bestenlehner, J M; Crowther, P A; García, M; Herrero, A; Sana, H; Simón-Díaz, S; Taylor, W D; van Loon, J Th; Vink, J S; Walborn, N R

    2014-01-01

    Context: The commonly used extinction laws of Cardelli et al. (1989) have limitations that, among other issues, hamper the determination of the effective temperatures of O and early B stars from optical+NIR photometry. Aims: We aim to develop a new family of extinction laws for 30 Doradus, check their general applicability within that region and elsewhere, and apply them to test the feasibility of using optical+NIR photometry to determine the effective temperature of OB stars. Methods: We use spectroscopy and NIR photometry from the VLT-FLAMES Tarantula Survey and optical photometry from HST/WFC3 of 30 Doradus and we analyze them with the software code CHORIZOS using different assumptions such as the family of extinction laws. Results: We derive a new family of optical+NIR extinction laws for 30 Doradus and confirm its applicability to extinguished Galactic O-type systems. We conclude that by using the new extinction laws it is possible to measure the effective temperatures of OB stars with moderate uncertain...

  13. The VLT-FLAMES Tarantula Survey. III. A very massive star in apparent isolation from the massive cluster R136

    NARCIS (Netherlands)

    Bestenlehner, J.M.; Vink, J.S.; Gräfener, G.; Najarro, F.; Evans, C.J.; Bastian, N.; Bonanos, A.Z.; Bressert, E.; Crowther, P.A.; Doran, E.; Friedrich, K.; Hénault-Brunet, V.; Herrero, A.; de Koter, A.; Langer, N.; Lennon, D.J.; Maíz Apellániz, J.; Sana, H.; Soszynski, I.; Taylor, W.D.

    2011-01-01

    VFTS 682 is located in an active star-forming region, at a projected distance of 29 pc from the young massive cluster R136 in the Tarantula Nebula of the Large Magellanic Cloud. It was previously reported as a candidate young stellar object, and more recently spectroscopically revealed as a

  14. The FLAMES Tarantula Survey

    CERN Document Server

    Markova, N; Bastian, N; Beletsky, Y; Bestenlehner, J; Brott, I; Cantiello, M; Carraro, G; Clark, J; Crowther, P; de Koter, A; de Mink, S; Doran, E; Dufton, P; Dunstall, P; Gieles, M; Graefener, G; Henault-Brunet, V; Herrero, A; Howarth, I; Langer, N; Lennon, D; Apellaniz, J Maiz; Najarro, F; Puls, J; Sana, H; Simon-Diaz, S; Smartt, S; Stroud, V; Taylor, W; van Loon, J; Vink, J; Walborn, N

    2011-01-01

    The Tarantula survey is an ESO Large Programme which has obtained multi-epochs spectroscopy of over 800 massive stars in the 30 Dor region in the Large Magelanic Cloud. Here we briefly describe the main drivers of the survey and the observational material derived.

  15. The VLT-FLAMES Tarantula Survey. XVII. Physical and wind properties of massive stars at the top of the main sequence

    Science.gov (United States)

    Bestenlehner, J. M.; Gräfener, G.; Vink, J. S.; Najarro, F.; de Koter, A.; Sana, H.; Evans, C. J.; Crowther, P. A.; Hénault-Brunet, V.; Herrero, A.; Langer, N.; Schneider, F. R. N.; Simón-Díaz, S.; Taylor, W. D.; Walborn, N. R.

    2014-10-01

    The evolution and fate of very massive stars (VMS) is tightly connected to their mass-loss properties. Their initial and final masses differ significantly as a result of mass loss. VMS have strong stellar winds and extremely high ionising fluxes, which are thought to be critical sources of both mechanical and radiative feedback in giant H ii regions. However, how VMS mass-loss properties change during stellar evolution is poorly understood. In the framework of the VLT-Flames Tarantula Survey (VFTS), we explore the mass-loss transition region from optically thin O star winds to denser WNh Wolf-Rayet star winds, thereby testing theoretical predictions. To this purpose we select 62 O, Of, Of/WN, and WNh stars, an unprecedented sample of stars with the highest masses and luminosities known. We perform a spectral analysis of optical VFTS as well as near-infrared VLT/SINFONI data using the non-LTE radiative transfer code CMFGEN to obtain both stellar and wind parameters. For the first time, we observationally resolve the transition between optically thin O star winds and optically thick hydrogen-rich WNh Wolf-Rayet winds. Our results suggest the existence of a "kink" between both mass-loss regimes, in agreement with recent Monte Carlo simulations. For the optically thick regime, we confirm the steep dependence on the classical Eddington factor Γe from previous theoretical and observational studies. The transition occurs on the main sequence near a luminosity of 106.1L⊙, or a mass of 80 ... 90 M⊙. Above this limit, we find that - even when accounting for moderate wind clumping (with fv = 0.1) - wind mass-loss rates are enhanced with respect to standard prescriptions currently adopted in stellar evolution calculations. We also show that this results in substantial helium surface enrichment. Finally, based on our spectroscopic analyses, we are able to provide the most accurate ionising fluxes for VMS known to date, confirming the pivotal role of VMS in ionising and

  16. The VLT-FLAMES Tarantula Survey XIX. B-type Supergiants - Atmospheric Parameters and Nitrogen Abundances to Investigate the Role of Binarity and the Width of the Main Sequence

    CERN Document Server

    McEvoy, C M; Evans, C J; Kalari, V M; Markova, N; Simón-Díaz, S; Vink, J S; Walborn, N R; Crowther, P A; de Koter, A; de Mink, S E; Dunstall, P R; Hénault-Brunet, V; Herrero, A; Langer, N; Lennon, D J; Apellániz, J Maíz; Najarro, F; Puls, J; Sana, H; Schneider, F R N; Taylor, W D

    2014-01-01

    TLUSTY non-LTE model atmosphere calculations have been used to determine atmospheric parameters and nitrogen (N) abundances for 34 single and 18 binary B-type supergiants (BSGs). The effects of flux contribution from an unseen secondary were considered for the binary sample. We present the first systematic study of the incidence of binarity for a sample of BSGs across the theoretical terminal age main sequence (TAMS). To account for the distribution of effective temperatures of the BSGs it may be necessary to extend the TAMS to lower temperatures. This is consistent with the derived distribution of mass discrepancies, projected rotational velocities (vsini) and N abundances, provided that stars cooler than this temperature are post RSG objects. For the BSGs in the Tarantula and previous FLAMES surveys, most have small vsini. About 10% have larger vsini (>100 km/s) but surprisingly these show little or no N enhancement. All the cooler BSGs have low vsini of <70km/s and high N abundance estimates, implying t...

  17. Installation and first results of FLAMES, the VLT multifibre facility

    Science.gov (United States)

    Pasquini, Luca; Alonso, Jaime; Avila, Gerardo; Barriga, Pablo; Biereichel, Peter; Buzzoni, Bernard; Cavadore, Cyril; Cumani, Claudio; Dekker, Hans; Delabre, Bernard; Kaufer, Andreas; Kotzlowski, Heinz; Hill, Vanessa; Lizon, Jean-Luis; Nees, Walter; Santin, Paolo; Schmutzer, Ricardo; Kesteren, A. V.; Zoccali, Manuela

    2003-03-01

    FLAMES is the VLT Fibre Facility, installed and being commissioned at the Nasmyth A of UT2 (Kueyen Telescope). FLAMES has been built and assembled at the VLT telescope in about 4 years through an international collaboration between 10 institutes in 6 countries and 3 continents. It had first light with the fibre link to the red arm of UVES on April 1, and with the GIRAFFE spectrograph on July 3. We have not yet enough data to compare the observed vs. expected astronomical performances, although these first data are encouraging in many respects. We aim at proceeding soon with the remaining tests

  18. The VLT-FLAMES Tarantula Survey. XXIII: two massive double-lined binaries in 30~Doradus

    CERN Document Server

    Howarth, Ian D; Dunstall, P R; Evans, C J; Almeida, L A; Bonanos, A Z; Clark, J S; Langer, N; Sana, H; Simon-Diaz, S; Soszynski, I; Taylor, W D

    2015-01-01

    We investigate the characteristics of two newly discovered short-period, double-lined, massive binary systems, VFTS 450 (O9.7$\\;$II--Ib$\\,$+$\\,$O7::) and VFTS 652 (B1$\\;$Ib$\\,+\\,$O9:$\\;$III:). We perform model-atmosphere analyses to characterise the photospheric properties of both members of each binary (denoting the `primary' as the spectroscopically more conspicuous component). Radial velocities and optical photometry are used to estimate the binary-system parameters. We estimate $T_{\\rm eff}=27$ kK, $\\log{(g)}=2.9$ (cgs) for the VFTS 450 primary spectrum (34kK, 3.6: for the secondary spectrum); and $T_{\\rm eff} = 22$kK, $\\log{(g)}=2.8$ for the VFTS 652 primary spectrum (35kK, 3.7: for the secondary spectrum). Both primaries show surface nitrogen enrichments (of more than 1 dex for VFTS 652), and probable moderate oxygen depletions relative to reference LMC abundances. We determine orbital periods of 6.89d and 8.59d for VFTS 450 and VFTS 652, respectively, and argue that the primaries must be close to filli...

  19. Two Remarkable Spectroscopic Categories of Young O Stars from the VLT-FLAMES Tarantula Survey

    CERN Document Server

    Walborn, Nolan R; Taylor, William D; Simon-Diaz, Sergio; Evans, Christopher J

    2011-01-01

    The spectral and spatial characteristics of two special categories of O stars found in the VFTS dataset are presented. One of them comprises very rapid rotators, including several more extreme than any previously known. These objects are distributed around the peripheries of the main 30 Doradus clusters, suggesting a runaway nature for which their radial velocities already provide preliminary supporting evidence. The other category consists of a large number of Vz stars, previously hypothesized on spectroscopic grounds to be on or very near the ZAMS. Their distribution is the inverse of that of the rapid rotators: the Vz are strongly concentrated to the ionizing clusters, plus a newly recognized band of recent and current star formation to the north, which provides strong circumstantial evidence for their extreme youth.

  20. The VLT-FLAMES Tarantula Survey VIII. Multiplicity properties of the O-type star population

    CERN Document Server

    Sana, H; de Mink, S E; Dunstall, P R; Evans, C J; Henault-Brunet, V; Apellaniz, J Maiz; Ramirez-Agudelo, O H; Taylor, W D; Walborn, N R; Clark, J S; Crowther, P A; Herrero, A; Gieles, M; Langer, N; Lennon, D J; Vink, J S

    2012-01-01

    Aims. We analyze the multiplicity properties of the massive O-type star population. With 360 O-type stars, this is the largest homogeneous sample of massive stars analyzed to date. Methods. We use multi-epoch spectroscopy and variability analysis to identify spectroscopic binaries. We also use a Monte-Carlo method to correct for observational biases. Results. We observe a spectroscopic binary fraction of 0.35\\pm0.03, which corresponds to the fraction of objects displaying statistically significant radial velocity variations with an amplitude of at least 20km/s. We compute the intrinsic binary fraction to be 0.51\\pm0.04. We adopt power-laws to describe the intrinsic period and mass-ratio distributions: f_P ~ (log P)^\\pi\\ (with 0.15 7.8', i.e. approx117 pc) and among the O9.7 I/II objects are however significantly lower than expected from statistical fluctuations. Conclusions. Using simple evolutionary considerations, we estimate that over 50% of the current O star population in 30 Dor will exchange mass with ...

  1. A high-resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy

    NARCIS (Netherlands)

    Letarte, B.; Hill, V.; Tolstoy, E.; Jablonka, P.; Shetrone, M.; Venn, K. A.; Spite, M.; Irwin, M. J.; Battaglia, G.; Helmi, A.; Primas, F.; François, P.; Kaufer, A.; Szeifert, T.; Arimoto, N.; Sadakane, K.

    2010-01-01

    For the first time we show the detailed, late-stage, chemical evolution history of a small nearby dwarf spheroidal galaxy in the Local Group. We present the results of a high-resolution (R ~ 20 000, λ = 5340-5620; 6120-6701) FLAMES/GIRAFFE abundance study at ESO/VLT of 81 photometrically selected, r

  2. A high-resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy

    NARCIS (Netherlands)

    Letarte, B.; Hill, V.; Tolstoy, E.; Jablonka, P.; Shetrone, M.; Venn, K. A.; Spite, M.; Irwin, M. J.; Battaglia, G.; Helmi, A.; Primas, F.; François, P.; Kaufer, A.; Szeifert, T.; Arimoto, N.; Sadakane, K.

    2010-01-01

    For the first time we show the detailed, late-stage, chemical evolution history of a small nearby dwarf spheroidal galaxy in the Local Group. We present the results of a high-resolution (R similar to 20 000, lambda = 5340-5620; 6120-6701) FLAMES/GIRAFFE abundance study at ESO/VLT of 81 photometrical

  3. Tarantula spider

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/002855.htm Tarantula spider bite To use the sharing features on this ... This article describes the effects of a tarantula spider bite. This article is for information only. DO ...

  4. VLT/FLAMES spectroscopy of Red Giant Branch stars in the Carina dwarf spheroidal galaxy

    CERN Document Server

    Lemasle, B; Tolstoy, E; Venn, K A; Shetrone, M D; Irwin, M J; de Boer, T J L; Starkenburg, E; Salvadori, S

    2011-01-01

    The ages of individual Red Giant Branch stars (RGB) can range from 1 Gyr old to the age of the Universe, and it is believed that the abundances of most chemical elements in their photospheres remain unchanged with time (those that are not affected by the 1st dredge-up). This means that they trace the ISM in the galaxy at the time the star formed, and hence the chemical enrichment history of the galaxy. CMD analysis has shown the Carina dwarf spheroidal (dSph) to have had an unusually episodic star formation history (SFH) which is expected to be reflected in the abundances of different chemical elements. We use the VLT-FLAMES spectrograph in HR mode (R~20000) to measure the abundances of several chemical elements in a sample of 35 RGB stars in Carina. We also combine these abundances with photometry to derive age estimates for these stars. This allows us to determine which of two distinct star formation (SF) episodes the stars in our sample belong to, and thus to define the relationship between SF and chemical...

  5. VLT/FLAMES spectroscopy of red giant branch stars in the Fornax dwarf spheroidal galaxy

    CERN Document Server

    Lemasle, B; Hill, V; Tolstoy, E; Irwin, M; Jablonka, P; Venn, K; Battaglia, G; Starkenburg, E; Shetrone, M; Letarte, B; Francois, P; Helmi, A; Primas, F; Kaufer, A; Szeifert, T

    2014-01-01

    Fornax is one of the most massive dwarf spheroidal galaxies in the Local Group. The Fornax field star population is dominated by intermediate age stars but star formation was going on over almost its entire history. It has been proposed that Fornax experienced a minor merger event. Despite recent progress, only the high metallicity end of Fornax field stars ([Fe/H]>-1.2 dex) has been sampled in larger number via high resolution spectroscopy. We want to better understand the full chemical evolution of this galaxy by better sampling the whole metallicity range, including more metal poor stars. We use the VLT-FLAMES multi-fibre spectrograph in high-resolution mode to determine the abundances of several alpha, iron-peak and neutron-capture elements in a sample of 47 individual Red Giant Branch stars in the Fornax dwarf spheroidal galaxy. We combine these abundances with accurate age estimates derived from the age probability distribution from the colour-magnitude diagram of Fornax. Similar to other dwarf spheroid...

  6. The VLT-FLAMES Tarantula Survey. IV: Candidates for isolated high-mass star formation in 30 Doradus

    NARCIS (Netherlands)

    Bressert, E.; Bastian, N.; Evans, C.J.; Sana, H.; Hénault-Brunet, V.; Goodwin, S.P.; Parker, R.J.; Gieles, M.; Bestenlehner, J.M.; Vink, J.S.; Taylor, W.D.; Crowther, P.A.; Longmore, S.N.; Gräfener, G.; Maíz Apellániz, J.; de Koter, A.; Cantiello, M.; Kruijssen, J.M.D.

    2012-01-01

    Whether massive stars (≳30 M⊙) can occasionally form in relative isolation (e.g. in clusters with M < 100 M⊙) or if they require a large cluster of lower-mass stars around them is a key test in the differentiation of star-formation theories as well as how the initial mass function of stars is sample

  7. The VLT-FLAMES Tarantula Survey. VI. Evidence for rotation of the young massive cluster R136

    NARCIS (Netherlands)

    Hénault-Brunet, V.; Gieles, M.; Evans, C.J.; Sana, H.; Bastian, N.; Maíz Apellániz, J.; Taylor, W.D.; Markova, N.; Bressert, E.; de Koter, A.; van Loon, J.T.

    2012-01-01

    Although it has important ramifications for both the formation of star clusters and their subsequent dynamical evolution, rotation remains a largely unexplored characteristic of young star clusters (few Myr). Using multi-epoch spectroscopic data of the inner regions of 30 Doradus in the Large

  8. The VLT-FLAMES Tarantula Survey. VII. A low velocity dispersion for the young massive cluster R136

    NARCIS (Netherlands)

    Hénault-Brunet, V.; Evans, C.J.; Sana, H.; Gieles, M.; Bastian, N.; Maíz Apellániz, J.; Markova, N.; Taylor, W.D.; Bressert, E.; Crowther, P.A.; van Loon, J.T.

    2012-01-01

    Detailed studies of resolved young massive star clusters are necessary to determine their dynamical state and evaluate the importance of gas expulsion and early cluster evolution. In an effort to gain insight into the dynamical state of the young massive cluster R136 and obtain the first measurement

  9. The VLT-FLAMES Tarantula survey XX. The nature of the X-ray bright emission line star VFTS 399

    CERN Document Server

    Clark, J S; Broos, P S; Townsley, L K; Taylor, W D; Walborn, N R; Bird, A J; Sana, H; de Mink, S E; Dufton, P L; Evans, C J; Langer, N; Apellániz, J Maíz; Schneider, F R N; Soszyński, I

    2015-01-01

    The stellar population of the 30 Doradus star-forming region in the Large Magellanic Cloud contains a subset of apparently single, rapidly rotating O-type stars. The physical processes leading to the formation of this cohort are currently uncertain. One member of this group, the late O-type star VFTS 399, is found to be unexpectedly X-ray bright for its bolometric luminosity - in this study we aim to determine its physical nature and the cause of this behaviour. We find VFTS 399 to be an aperiodic photometric variable with an apparent near-IR excess. Its optical spectrum demonstrates complex emission profiles in the lower Balmer series and select HeI lines - taken together these suggest an OeBe classification. The highly variable X-ray luminosity is too great to be produced by a single star, while the hard, non-thermal nature suggests the presence of an accreting relativistic companion. Finally, the detection of periodic modulation of the X-ray lightcurve is most naturally explained under the assumption that ...

  10. The VLT-FLAMES Tarantula Survey - XI. A census of the hot luminous stars and their feedback in 30 Doradus

    CERN Document Server

    Doran, E I; de Koter, A; Evans, C J; McEvoy, C; Walborn, N R; Bastian, N; Bestenlehner, J M; Grafener, G; Herrero, A; Kohler, K; Apellaniz, J Maiz; Najarro, F; Puls, J; Sana, H; Schneider, F R N; Taylor, W D; van Loon, J Th; Vink, J S

    2013-01-01

    We compile the first comprehensive census of hot luminous stars in the 30 Doradus (30 Dor) star forming region of the LMC. The census extends to a radius of 10arcmin (150pc) from the central cluster, R136. Stars were selected photometrically and combined with the latest spectral types. 1145 candidate hot luminous stars were identified of which >700 were considered genuine early type stars that contribute to feedback. We assess the spectroscopic completeness to be 85% in outer regions (>5pc) but fall to 35% in the vicinity of R136, giving a total of 500 hot luminous stars with spectroscopy. Stellar calibrations and models were used to obtain their physical parameters before integrated values were compared to global observations and the population synthesis code, Starburst99. The 31 W-R and Of/WN stars made large contributions to the total ionising and wind luminosities of ~40% and ~50%, respectively. Stars with Minit>100Msun also showed high contributions to the global feedback, ~25% in both cases. Such massiv...

  11. Integral Field Spectroscopy of Protoplanetary Disks in Orion with VLT FLAMES

    Science.gov (United States)

    Tsamis, Y. G.; Walsh, J. R.; Péquignot, D.

    We discuss integral field spectroscopy of proplyds in M42 using the FLAMES Argus unit and report the first detection of recombination lines of C II and O II from the archetypical LV2 object. These lines can provide important new diagnostics of the physical conditions in proplyds. We also draw attention to the future capabilities of the MUSE spectrograph in relation to similar studies.

  12. Integral field spectroscopy of protoplanetary disks in Orion with VLT FLAMES

    CERN Document Server

    Tsamis, Y G; Péquignot, D

    2008-01-01

    We discuss integral field spectroscopy of proplyds in M42 using the FLAMES Argus unit and report the first detection of recombination lines of C II and O II from the archetypical Laques-Vidal-2 object. These lines can provide important new diagnostics of the physical conditions in proplyds. We also draw attention to the future capabilities of the MUSE spectrograph in relation to similar studies.

  13. Integral field spectroscopy of planetary nebulae: mapping the line diagnostics and hydrogen-poor zones with VLT FLAMES

    CERN Document Server

    Tsamis, Y G; Péquignot, D; Barlow, M J; Danziger, I J; Liu, X -W

    2008-01-01

    (Abridged) Results from the first dedicated study of Galactic PNe by means of optical integral field spectroscopy with the VLT FLAMES Argus IFU are presented. Three typical Galactic-disk PNe have been mapped with the 11.5''x7.2'' Argus array: two dimensional spectral maps of NGC 5882, 6153 and 7009 with 297 spatial pixels per target were obtained at sub-arcsec resolutions and 297 spectra per target were obtained in the 396.4-507.8 nm range. Spatially resolved maps of emission lines and of nebular physical properties were produced. The abundances of helium and of doubly ionized carbon and oxygen were derived from optical recombination lines (ORLs), while those of O^2+ were also derived from the collisionally excited lines (CELs). The abundance discrepancy problem was investigated by mapping the ratio of ORL/CEL abundances for O^2+ (the abundance discrepancy factor; ADF) across the face of the PNe. The ADF varies between targets and also with position within the targets attaining values of ~40 in the case of NG...

  14. A VLT/FLAMES STUDY OF THE PECULIAR INTERMEDIATE-AGE LARGE MAGELLANIC CLOUD STAR CLUSTER NGC 1846. I. KINEMATICS

    Energy Technology Data Exchange (ETDEWEB)

    Mackey, A. D.; Da Costa, G. S.; Yong, D. [Research School of Astronomy and Astrophysics, The Australian National University, Mount Stromlo Observatory, via Cotter Road, Weston, ACT 2611 (Australia); Ferguson, A. M. N., E-mail: dougal@mso.anu.edu.au [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom)

    2013-01-01

    In this paper we present high-resolution VLT/FLAMES observations of red giant stars in the massive intermediate-age Large Magellanic Cloud star cluster NGC 1846, which, on the basis of its extended main-sequence turnoff (EMSTO), possesses an internal age spread of Almost-Equal-To 300 Myr. We describe in detail our target selection and data reduction procedures, and construct a sample of 21 stars possessing radial velocities indicating their membership of NGC 1846 at high confidence. We consider high-resolution spectra of the planetary nebula Mo-17, and conclude that this object is also a member of the cluster. Our measured radial velocities allow us to conduct a detailed investigation of the internal kinematics of NGC 1846, the first time this has been done for an EMSTO system. The key result of this work is that the cluster exhibits a significant degree of systemic rotation, of a magnitude comparable to the mean velocity dispersion. Using an extensive suite of Monte Carlo models we demonstrate that, despite our relatively small sample size and the substantial fraction of unresolved binary stars in the cluster, the rotation signal we detect is very likely to be genuine. Our observations are in qualitative agreement with the predictions of simulations modeling the formation of multiple populations of stars in globular clusters, where a dynamically cold, rapidly rotating second generation is a common feature. NGC 1846 is less than one relaxation time old, so any dynamical signatures encoded during its formation ought to remain present.

  15. Rotational properties of the O-type star population in the Tarantula region

    CERN Document Server

    Ramírez-Agudelo, O H; Sana, H; de Koter, A; Sabín-Sanjulían, C; de Mink, S E; Dufton, P L; Gräfener, G; Evans, C J; Herrero, A; Langer, N; Lennon, D J; Apellániz, J Maíz; Markova, N; Najarro, F; Puls, J; Taylor, W D; Vink, J S

    2013-01-01

    The 30 Doradus (30\\,Dor) region in the Large Magellanic Cloud (also known as the Tarantula Nebula) is the nearest massive starburst region, containing the richest sample of massive stars in the Local Group. It is the best possible laboratory to investigate aspects of the formation and evolution of massive stars. Here, we focus on rotation which is a key parameter in the evolution of these objects. We establish the projected rotational velocity, $v_{e}\\sin i$, distribution of an unprecedented sample of 216 radial velocity constant ($\\rm{\\Delta RV\\, \\leq\\, 20 \\,km s^{-1}}$) O-type stars in 30\\,Dor observed in the framework of the VLT-FLAMES Tarantula Survey (VFTS). The distribution of $v_{e}\\sin i$ shows a two-component structure: a peak around 80 $\\rm{km s^{-1}}$ and a high-velocity tail extending up to $\\sim$600 $\\rm{km s^{-1}}$. Around 75% of the sample has 0 $\\leq\\, v_{e}\\sin i \\leq$ 200 $\\rm{km s^{-1}}$ with the other 25% distributed in the high-velocity tail. The presence of the low-velocity peak is consi...

  16. The VLT-FLAMES Tarantula Survey: The fastest rotating O-type star and shortest period LMC pulsar - remnants of a supernova disrupted binary?

    CERN Document Server

    Dufton, P L; Evans, C J; Brott, I; Cantiello, M; de Koter, A; de Mink, S E; Fraser, M; Hénault-Brunet, V; Howarth, I D; Langer, N; Lennon, D J; Markova, N; Sana, H; Taylor, W D

    2011-01-01

    We present a spectroscopic analysis of an extremely rapidly rotating late O-type star, VFTS102, observed during a spectroscopic survey of 30 Doradus. VFTS102 has a projected rotational velocity larger than 500\\kms\\ and probably as large as 600\\kms; as such it would appear to be the most rapidly rotating massive star currently identified. Its radial velocity differs by 40\\kms\\ from the mean for 30 Doradus, suggesting that it is a runaway. VFTS102 lies 12 pcs from the X-ray pulsar PSR J0537-6910 in the tail of its X-ray diffuse emission. We suggest that these objects originated from a binary system with the rotational and radial velocities of VFTS102 resulting from mass transfer from the progenitor of PSR J0537-691 and the supernova explosion respectively.

  17. Broad Balmer Wings in BA Hyper/Supergiants Distorted by Diffuse Interstellar Bands: Five Examples in the 30 Doradus Region from the VLT-FLAMES Tarantula Survey

    CERN Document Server

    Walborn, Nolan R; Evans, Christopher J; Taylor, William D; Sabbi, Elena; Barbá, Rodolfo H; Morrell, Nidia I; Apellániz, Jesús Maíz; Sota, Alfredo; Dufton, Philip L; McEvoy, Catherine M; Clark, J Simon; Markova, Nevena; Ulaczyk, Krzysztof

    2015-01-01

    Extremely broad emission wings at H$\\beta$ and H$\\alpha$ have been found in VFTS data for five very luminous BA supergiants in or near 30 Doradus in the Large Magellanic Cloud. The profiles of both lines are extremely asymmetrical, which we have found to be caused by very broad diffuse interstellar bands (DIBs) in the longward wing of H$\\beta$ and the shortward wing of H$\\alpha$. These DIBs are well known to interstellar but not to many stellar specialists, so that the asymmetries may be mistaken for intrinsic features. The broad emission wings are generally ascribed to electron scattering, although we note difficulties for that interpretation in some objects. Such profiles are known in some Galactic hyper/supergiants and are also seen in both active and quiescent Luminous Blue Variables. No prior or current LBV activity is known in these 30 Dor stars, although a generic relationship to LBVs is not excluded; subject to further observational and theoretical investigation, it is possible that these very luminou...

  18. Rotational velocities of single and binary O-type stars in the Tarantula Nebula

    CERN Document Server

    Ramírez-Agudelo, O H; de Koter, A; Simón-Díaz, S; de Mink, S E; Tramper, F; Dufton, P L; Evans, C J; Gräfener, G; Herrero, A; Langer, N; Lennon, D J; Apellániz, J Maíz; Markova, N; Najarro, F; Puls, J; Taylor, W D; Vink, J S

    2014-01-01

    Rotation is a key parameter in the evolution of massive stars, affecting their evolution, chemical yields, ionizing photon budget, and final fate. We determined the projected rotational velocity, $v_e\\sin i$, of $\\sim$330 O-type objects, i.e. $\\sim$210 spectroscopic single stars and $\\sim$110 primaries in binary systems, in the Tarantula nebula or 30 Doradus (30\\,Dor) region. The observations were taken using VLT/FLAMES and constitute the largest homogeneous dataset of multi-epoch spectroscopy of O-type stars currently available. The most distinctive feature of the $v_e\\sin i$ distributions of the presumed-single stars and primaries in 30 Dor is a low-velocity peak at around 100\\,$\\rm{km s^{-1}}$. Stellar winds are not expected to have spun-down the bulk of the stars significantly since their arrival on the main sequence and therefore the peak in the single star sample is likely to represent the outcome of the formation process. Whereas the spin distribution of presumed-single stars shows a well developed tai...

  19. The Hubble Tarantula Treasury Project

    Science.gov (United States)

    Sabbi, Elena; Lennon, D. J.; Anderson, J.; Van Der Marel, R. P.; Aloisi, A.; Boyer, M. L.; Cignoni, M.; De Marchi, G.; de Mink, S. E.; Evans, C. J.; Gallagher, J. S.; Gordon, K. D.; Gouliermis, D.; Grebel, E.; Koekemoer, A. M.; Larsen, S. S.; Panagia, N.; Ryon, J. E.; Smith, L. J.; Tosi, M.; Zaritsky, D. F.

    2014-01-01

    The Tarantula Nebula (a.k.a. 30 Doradus) in the Large Magellanic Cloud is one of the most famous objects in astronomy, with first astronomical references being more than 150 years old. Today the Tarantula Nebula and its ionizing cluster R136 are considered one of the few known starburst regions in the Local Group and an ideal test bed to investigate the temporal and spatial evolution of a prototypical starburst on a sub-cluster scale. The Hubble Tarantula Treasury Project (HTTP) is a panchromatic imaging survey of the stellar populations and ionized gas in the Tarantula Nebula that reaches into the sub-solar mass regime (eBook that explains how stars form and evolve using images from HTTP. The eBook utilizes emerging technology that works in conjunction with the built-in accessibility features in the Apple iPad to allow totally blind users to interactively explore complex astronomical images.

  20. Happy Anniversary, VLT !

    Science.gov (United States)

    2004-04-01

    Telescopes (UTs) and will in due time also include four moving 1.8-m Auxiliary Telescopes (ATs), the first one of which successfully passed its first tests in January of this year (see ESO PR 01/04). With unprecedented optical resolution and unsurpassed surface area, the VLT produces extremely sharp images and can record light from the faintest and most remote objects in the Universe. It works at the limit of modern technology, regularly allowing the scientists to peer into new and unknown territories in the immense Universe. Contrary to other large astronomical telescopes, the VLT was designed from the beginning with the use of interferometry as a major goal. For this reason, the four 8.2-m Unit Telescopes were positioned in a quasi-trapezoidal configuration. The light beams from these telescopes, at this moment two-by-two, can be combined in the VLT Interferometer (VLTI). It provides the European scientific community with a ground-based telescope array with collecting power significantly greater than any other facilities available at present or being planned, offering imaging and spectroscopy capabilities at visible and infrared wavelengths. Seven of the planned ten first-generation astronomical instruments are now in operation at the VLT. They cover all major observing modes required to tackle current "hot", front-line research topics: * the multi-mode instrument FORS1 (FOcal Reducer and Spectrograph) and its twin, FORS2, * the Infrared Spectrometer And Array Camera (ISAAC) cryogenic infrared imager and spectrometer, * the UVES (Ultra-violet and Visible Echelle Spectrograph) high-dispersion spectrograph, * the NAOS-CONICA Adaptive Optics facility producing images as sharp as if taken in space [2], * the VIsible Multi-Object Spectrograph (VIMOS) four-channel multiobject spectrograph and imager - allowing to obtain low-resolution spectra of up to 1000 galaxies at a time * the Fibre Large Array Multi-Element Spectrograph (FLAMES) that offers the unique capability to study

  1. TARANTULA 2011 in JWL++

    Energy Technology Data Exchange (ETDEWEB)

    Souers, P C; Haylett, D; Vitello, P

    2011-10-27

    Using square zoning, the 2011 version of the kinetic package Tarantula matches cylinder data, cylinder dead zones, and cylinder failure with the same settings for the first time. The key is the use of maximum pressure rather than instantaneous pressure. Runs are at 40, 200 and 360 z/cm using JWL++ as the host model. The model also does run-to-detonation, thin-pulse initiation with a P-t curve and air gap crossing, all in cylindrical geometry. Two sizes of MSAD/LX-10/LX-17 snowballs work somewhat with these settings, but are too weak, so that divergent detonation is a challenge for the future. Butterfly meshes are considered but do not appear to solve the issue.

  2. "Tarantula keratitis": a case report.

    LENUS (Irish Health Repository)

    McAnena, L

    2013-09-01

    A case of an 11-year-old boy presenting with a two-week history of a red, irritated right eye after handling a Chilean Rose Tarantula at an exotic pet exhibition. Examination revealed innumerable microscopic hairs embedded at all levels of the cornea. He was commenced on steroid drops with subjective and objective improvement at follow up.

  3. Multiple Eyes for the VLT

    Science.gov (United States)

    2002-01-01

    First System of Deployable Multi-Integral Field Units Ready Summary The ESO Very Large Telescope (VLT) at the Paranal Observatory is being equipped with many state-of-the-art astronomical instruments that will allow observations in a large number of different modes and wavebands. Soon to come is the Fibre Large Array Multi-Element Spectrograph (FLAMES) , a project co-ordinated by ESO. It incorporates several complex components, now being constructed at various research institutions in Europe and Australia. One of these, a true technological feat, is a unique system of 15 deployable fibre bundles, the so-called Integral Field Units (IFUs) . They can be accurately positioned within a sky field-of-view measuring no less that 25 arcmin in diameter, i.e., almost as large as the full Moon . Each of the IFUs looks like an insect's eye and images a small sky area (3 x 2 arcsec 2 ) with a multiple microlens. From each IFU, 20 narrow light beams are sent via optical fibres to an advanced spectrograph. All 300 spectra are recorded simultaneously by a sensitive digital camera. A major advantage of this technique is that, contrary usual spectroscopic observations in which spectral information is obtained along a (one-dimensional) line on the sky, it now allows (two-dimensional) area spectroscopy . This will permit extremely efficient spectral observations of many celestial objects, including faint galaxies, providing detailed information about their internal structure and motions. Such studies will have an important impact on our understanding, e.g., of the early evolution of galaxies , the main building blocks in the Universe. The IFUs have been developed by a team of astronomers and engineers [2] at the Observatoire de Paris-Meudon. All IFU components are now at the ESO Headquarters in Garching (Germany) where they are being checked and integrated into the instrument [3]. PR Photo 03a/02 : The GIRAFFE spectrograph in the ESO Assembly Hall (Garching, Germany) . PR Photo 03b/02

  4. Tarantula Hairs as Corneal Foreign Bodies

    Directory of Open Access Journals (Sweden)

    Brian C. Stagg

    2011-10-01

    Full Text Available Purpose: To report a case of tarantula hairs found in the cornea and discuss treatment. Case Report: A 16-year-old male presented with a 6-week history of right ocular irritation that began after letting his pet tarantula crawl on his face. Slit-lamp examination of the right eye revealed the presence of approximately 16 dark foreign bodies that had the appearance of small hairs. The foreign bodies were removed from the nasal region of the right cornea using Jewelers forceps, and the patient was prescribed a combination neomycin, polymyxin B, and dexamethasone ointment (Maxitrol®, given 4 times per day. Results: The patient presented for follow-up 2 weeks later, with resolution of symptoms. Conclusion: Effective treatment of keratitis caused by tarantula hairs includes taking a detailed history, conducting a careful slit-lamp examination, removal of any accessible hairs, and initiation of treatment with a topical steroid as determined by the clinical picture.

  5. Tarantula: Killing driver bugs before they hatch

    DEFF Research Database (Denmark)

    Lawall, Julia Laetitia; Muller, Gilles; Urunuela, Richard

    2005-01-01

    The Linux operating system is undergoing continual evolution. Evolution in the kernel and generic driver modules often triggers the need for corresponding evolutions in specific device drivers. Such collateral evolutions are tedious, because of the large number of device drivers, and error......-prone, because of the complexity of the code modifications involved. We propose an automatic tool, Tarantula, to aid in this process. In this paper, we examine some recent evolutions in Linux and the collateral evolutions they trigger, and assess the corresponding requirements on Tarantula....

  6. Tarantula: Killing driver bugs before they hatch

    DEFF Research Database (Denmark)

    Lawall, Julia Laetitia; Muller, Gilles; Urunuela, Richard

    2005-01-01

    The Linux operating system is undergoing continual evolution. Evolution in the kernel and generic driver modules often triggers the need for corresponding evolutions in specific device drivers. Such collateral evolutions are tedious, because of the large number of device drivers, and error......-prone, because of the complexity of the code modifications involved. We propose an automatic tool, Tarantula, to aid in this process. In this paper, we examine some recent evolutions in Linux and the collateral evolutions they trigger, and assess the corresponding requirements on Tarantula....

  7. Hubble Tarantula Treasury Project: Unraveling Tarantula's Web. I. Observational overview and first results

    CERN Document Server

    Sabbi, E; Lennon, D J; van der Marel, R P; Aloisi, A; Boyer, M L; Cignoni, M; de Marchi, G; de Mink, S E; Evans, C J; Gallagher, J S; Gordon, K; Gouliermis, D A; Grebel, E K; Koekemoer, A M; Larsen, S S; Panagia, N; Ryon, J E; Smith, L J; Tosi, M; Zaritsky, D

    2013-01-01

    The Hubble Tarantula Treasury Project (HTTP) is an ongoing panchromatic imaging survey of stellar populations in the Tarantula Nebula in the Large Magellanic Cloud that reaches into the sub-solar mass regime (< 0.5 Mo). HTTP utilizes the capability of HST to operate the Advanced Camera for Surveys (ACS) and the Wide Field Camera 3 (WFC3) in parallel to study this remarkable region in the near-ultraviolet, optical, and near-infrared spectral regions, including narrow band H$\\alpha$ images. The combination of all these bands provides a unique multi-band view. The resulting maps of the stellar content of the Tarantula Nebula within its main body provide the basis for investigations of star formation in an environment resembling the extreme conditions found in starburst galaxies and in the early Universe. Access to detailed properties of individual stars allows us to begin to reconstruct the evolution of the stellar skeleton of the Tarantula Nebula over space and time with parcsec-scale resolution. In this fir...

  8. Hubble Tarantula Treasury Project: Unraveling Tarantula's Web. I. Observational Overview and First Results

    Science.gov (United States)

    Sabbi, E.; Anderson, J.; Lennon, D. J.; van der Marel, R. P.; Aloisi, A.; Boyer, Martha L.; Cignoni, M.; De Marchi, G.; De Mink, S. E.; Evans, C. J.; hide

    2013-01-01

    The Hubble Tarantula Treasury Project (HTTP) is an ongoing panchromatic imaging survey of stellar populations in the Tarantula Nebula in the Large Magellanic Cloud that reaches into the sub-solar mass regime (Hubble Space Telescope to operate the Advanced Camera for Surveys and the Wide Field Camera 3 in parallel to study this remarkable region in the near-ultraviolet, optical, and near-infrared spectral regions, including narrow-band H(alpha) images. The combination of all these bands provides a unique multi-band view. The resulting maps of the stellar content of the Tarantula Nebula within its main body provide the basis for investigations of star formation in an environment resembling the extreme conditions found in starburst galaxies and in the early universe. Access to detailed properties of individual stars allows us to begin to reconstruct the temporal and spatial evolution of the stellar skeleton of the Tarantula Nebula over space and time on a sub-parsec scale. In this first paper we describe the observing strategy, the photometric techniques, and the upcoming data products from this survey and present preliminary results obtained from the analysis of the initial set of near-infrared observations.

  9. HUBBLE TARANTULA TREASURY PROJECT: UNRAVELING TARANTULA'S WEB. I. OBSERVATIONAL OVERVIEW AND FIRST RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Sabbi, E.; Anderson, J.; Van der Marel, R. P.; Aloisi, A.; De Mink, S. E.; Gordon, K.; Koekemoer, A. M.; Panagia, N. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Lennon, D. J. [ESA-European Space Astronomy Center, Apdo. de Correo 78, E-28691 Villanueva de la Canada, Madrid (Spain); Boyer, M. L. [Observational Cosmology Lab, Code 665, NASA, Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Cignoni, M. [Dipartimento di Astronomia, Universita degli Studi di Bologna, via Ranzani, I-40127 Bologna (Italy); De Marchi, G. [Space Science Department, European Space Agency, Keplerlaan 1, 2200-AG Noordwijk (Netherlands); Evans, C. J. [UK Astronomy Technology Center, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Gallagher, J. S. III; Ryon, J. E. [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Gouliermis, D. A. [Zentrum fuer Astronomie, Institut fuer Theoretische Astrophysik, Universitaet Heidelberg, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Grebel, E. K. [Zentrum fuer Astronomie, Astronomisches Rechen-Institut, Universitaet Heidelberg, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany); Larsen, S. S. [Department of Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500-GL Nijmegen (Netherlands); Smith, L. J. [ESA/STScI, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Tosi, M., E-mail: sabbi@stsci.edu [Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); and others

    2013-09-15

    The Hubble Tarantula Treasury Project (HTTP) is an ongoing panchromatic imaging survey of stellar populations in the Tarantula Nebula in the Large Magellanic Cloud that reaches into the sub-solar mass regime (<0.5 M{sub Sun }). HTTP utilizes the capability of the Hubble Space Telescope to operate the Advanced Camera for Surveys and the Wide Field Camera 3 in parallel to study this remarkable region in the near-ultraviolet, optical, and near-infrared spectral regions, including narrow-band H{alpha} images. The combination of all these bands provides a unique multi-band view. The resulting maps of the stellar content of the Tarantula Nebula within its main body provide the basis for investigations of star formation in an environment resembling the extreme conditions found in starburst galaxies and in the early universe. Access to detailed properties of individual stars allows us to begin to reconstruct the temporal and spatial evolution of the stellar skeleton of the Tarantula Nebula over space and time on a sub-parsec scale. In this first paper we describe the observing strategy, the photometric techniques, and the upcoming data products from this survey and present preliminary results obtained from the analysis of the initial set of near-infrared observations.

  10. Hubble Tarantula Treasury Project: Unraveling Tarantula's Web. I. Observational Overview and First Results

    Science.gov (United States)

    Sabbi, E.; Anderson, J.; Lennon, D. J.; van der Marel, R. P.; Aloisi, A.; Boyer, M. L.; Cignoni, M.; de Marchi, G.; de Mink, S. E.; Evans, C. J.; Gallagher, J. S., III; Gordon, K.; Gouliermis, D. A.; Grebel, E. K.; Koekemoer, A. M.; Larsen, S. S.; Panagia, N.; Ryon, J. E.; Smith, L. J.; Tosi, M.; Zaritsky, D.

    2013-09-01

    The Hubble Tarantula Treasury Project (HTTP) is an ongoing panchromatic imaging survey of stellar populations in the Tarantula Nebula in the Large Magellanic Cloud that reaches into the sub-solar mass regime (images. The combination of all these bands provides a unique multi-band view. The resulting maps of the stellar content of the Tarantula Nebula within its main body provide the basis for investigations of star formation in an environment resembling the extreme conditions found in starburst galaxies and in the early universe. Access to detailed properties of individual stars allows us to begin to reconstruct the temporal and spatial evolution of the stellar skeleton of the Tarantula Nebula over space and time on a sub-parsec scale. In this first paper we describe the observing strategy, the photometric techniques, and the upcoming data products from this survey and present preliminary results obtained from the analysis of the initial set of near-infrared observations. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555.

  11. Ground-based CCD astrometry with wide field imagers. II. A star catalogue for M67: WFI@2.2m MPG/ESO astrometry, FLAMES@VLT radial velocities

    CERN Document Server

    Yadav, R K S; Piotto, G; Anderson, J; Cassisi, S; Villanova, S; Platais, I; Pasquini, L; Momany, Y; Sagar, R

    2008-01-01

    The solar-age open cluster M67 (C0847+120, NGC2682) is a touchstone in studies of the old Galactic disk. Despite its outstanding role, the census of cluster membership for M67 at fainter magnitudes and their properties are not well-established. Using the proprietary and archival ESO data, we have obtained astrometric, photometric, and radial velocities of stars in a 34'x 33' field centered on the old open cluster M67. The two-epoch archival observations separated by 4 years and acquired with the Wide Field Imager at the 2.2m MPG/ESO telescope have been reduced with our new astrometric techniques, as described in the first paper of this series. The same observations served to derive calibrated BVI photometry in M67. Radial velocities were measured using the archival and new spectroscopic data obtained at VLT. We have determined relative proper motions and membership probabilities for ~2,400 stars. The precision of proper motions for optimally exposed stars is ~2 mas/yr, gradually degrading down to ~5 mas/yr at...

  12. Blue reflectance in tarantulas is evolutionarily conserved despite nanostructural diversity.

    Science.gov (United States)

    Hsiung, Bor-Kai; Deheyn, Dimitri D; Shawkey, Matthew D; Blackledge, Todd A

    2015-11-01

    Slight shifts in arrangement within biological photonic nanostructures can produce large color differences, and sexual selection often leads to high color diversity in clades with structural colors. We use phylogenetic reconstruction, electron microscopy, spectrophotometry, and optical modeling to show an opposing pattern of nanostructural diversification accompanied by unusual conservation of blue color in tarantulas (Araneae: Theraphosidae). In contrast to other clades, blue coloration in phylogenetically distant tarantulas peaks within a narrow 20-nm region around 450 nm. Both quasi-ordered and multilayer nanostructures found in different tarantulas produce this blue color. Thus, even within monophyletic lineages, tarantulas have evolved strikingly similar blue coloration through divergent mechanisms. The poor color perception and lack of conspicuous display during courtship of tarantulas argue that these colors are not sexually selected. Therefore, our data contrast with sexual selection that typically produces a diverse array of colors with a single structural mechanism by showing that natural selection on structural color in tarantulas resulted in convergence on similar color through diverse structural mechanisms.

  13. VLT Instruments Pipeline System Overview

    Science.gov (United States)

    Jung, Y.; Ballester, P.; Banse, K.; Hummel, W.; Izzo, C.; McKay, D. J.; Kiesgen, M.; Lundin, L. K.; Modigliani, A.; Palsa, R. M.; Sabet, C.

    2004-07-01

    Since the beginning of the VLT operations in 1998, substantial effort has been put in the development of automatic data reduction tools for the VLT instruments. A VLT instrument pipeline is a complex system that has to be able to identify and classify each produced FITS file, optionally retrieve calibration files from a database, use an image processing software to reduce the data, compute and log quality control parameters, produce FITS images or tables with the correct headers, optionally display them in the control room and send them to the archive. Each instrument has its own dedicated pipeline, based on a common infrastructure and installed with the VLT Data Flow System (DFS). With the increase in the number and the complexity of supported instruments and in the rate of produced data, these pipelines are becoming vital for both the VLT operations and the users, and request more and more resources for development and maintenance. This paper describes the different pipeline tasks with some real examples. It also explains how the development process has been improved to both decrease its cost and increase the pipelines quality using the lessons learned from the first instruments pipelines development.

  14. Toward accurate radial velocities with the fiber-fed GIRAFFE multi-object VLT spectrograph

    Science.gov (United States)

    Royer, Frederic; Blecha, Andre; North, Pierre; Simond, Gilles; Baratchart, Sebastien; Cayatte, Veronique; Chemin, Laurent; Palsa, Ralf

    2002-12-01

    We describe briefly the Data-Reduction of the VLT fiber-fed multi-object GIRAFFE spectrograph - part of the VLT FLAMES facility. We focus on specific features of GIRAFFE - the simultaneous wavelength calibration - and their impact on the data-reduction strategy. We describe the implementation of the global physical model and we compare the results obtained with the simulated, laboratory and preliminary data. We discuss the influence of critical parameters, the overall accuracy of the wavelength solution, and the stability and the robustness of the global model approach. We address the accuracy of radial velocity measurements illustrated by solar spectra obtained during the Preliminary Acceptance in Europe.

  15. Next VLT Instrument Ready for the Astronomers

    Science.gov (United States)

    2000-02-01

    FORS2 Commissioning Period Successfully Terminated The commissioning of the FORS2 multi-mode astronomical instrument at KUEYEN , the second FOcal Reducer/low dispersion Spectrograph at the ESO Very Large Telescope, was successfully finished today. This important work - that may be likened with the test driving of a new car model - took place during two periods, from October 22 to November 21, 1999, and January 22 to February 8, 2000. The overall goal was to thoroughly test the functioning of the new instrument, its conformity to specifications and to optimize its operation at the telescope. FORS2 is now ready to be handed over to the astronomers on April 1, 2000. Observing time for a six-month period until October 1 has already been allocated to a large number of research programmes. Two of the images that were obtained with FORS2 during the commissioning period are shown here. An early report about this instrument is available as ESO PR 17/99. The many modes of FORS2 The FORS Commissioning Team carried out a comprehensive test programme for all observing modes. These tests were done with "observation blocks (OBs)" that describe the set-up of the instrument and telescope for each exposure in all details, e.g., position in the sky of the object to be observed, filters, exposure time, etc.. Whenever an OB is "activated" from the control console, the corresponding observation is automatically performed. Additional information about the VLT Data Flow System is available in ESO PR 10/99. The FORS2 observing modes include direct imaging, long-slit and multi-object spectroscopy, exactly as in its twin, FORS1 at ANTU . In addition, FORS2 contains the "Mask Exchange Unit" , a motorized magazine that holds 10 masks made of thin metal plates into which the slits are cut by means of a laser. The advantage of this particular observing method is that more spectra (of more objects) can be taken with a single exposure (up to approximately 80) and that the shape of the slits can be

  16. The VLT Real Time Display

    Science.gov (United States)

    Herlin, T.; Brighton, A.; Biereichel, P.

    The VLT Real-Time Display (RTD) software was developed in order to support image display in real-time, providing a tool for users to display video like images from a camera or detector as fast as possible on an X-Server. The RTD software is implemented as a package providing a Tcl/Tk image widget written in C++ and an independent image handling library and can be used as a building block, adding display capabilities to dedicated VLT control applications. The RTD widget provides basic image display functionality like: panning, zooming, color scaling, colormaps, intensity changes, pixel query, overlaying of line graphics. A large set of assisting widgets, e.g., colorbar, zoom window, spectrum plot are provided to enable the building of image applications. The support for real-time is provided by an RTD image event mechanism used for camera or detector subsystems to pass images to the RTD widget. Image data are passed efficiently via shared memory. This paper describes the architecture of the RTD software and summarizes the features provided by RTD.

  17. The Tarantula Massive Binary Monitoring: I. Observational campaign and OB-type spectroscopic binaries

    CERN Document Server

    Almeida, L A; Taylor, W; Barbá, R; Bonanos, A; Crowther, P; Damineli, A; de Koter, A; de Mink, S E; Evans, C J; Gieles, M; Grin, N J; Hénault-Brunet, V; Langer, N; Lennon, D; Lockwood, S; Apellániz, J Maíz; Moffat, A F J; Neijssel, C; Norman, C; Ramírez-Agudelo, O H; Richardson, N D; Schootemeijer, A; Shenar, T; Soszyński, I; Tramper, F; Vink, J S

    2016-01-01

    Massive binaries (MBs) play a crucial role in the Universe and knowing the distributions of their orbital parameters (OPs) is important for a wide range of topics, from stellar feedback to binary evolution channels, from the distribution of supernova types to gravitational wave progenitors. Yet, no direct measurements exist outside the Milky Way. The Tarantula Massive Binary Monitoring was designed to help fill this gap by obtaining multi-epoch radial velocity monitoring of 102 MBs in the 30 Dor. In this paper, we analyse 32 FLAMES/GIRAFFE observations of 93 O- and 7 B-type binaries. We performed a Fourier analysis and obtained orbital solutions for 82 systems: 51 single-lined and 31 double-lined spectroscopic binaries. Overall, the OPs and binary fraction are remarkably similar across the 30 Dor region and compared to existing Galactic samples (GSs). This indicates that within these domains environmental effects are of second order in shaping the properties of MBs. A small difference is found in the distribu...

  18. VLT laser guide star facility

    Science.gov (United States)

    Bonaccini, Domenico; Allaert, Eric; Araujo, Constanza; Brunetto, Enzo; Buzzoni, Bernard; Comin, Mauro; Cullum, Martin J.; Davies, Richard I.; Dichirico, Canio; Dierickx, Philippe; Dimmler, Martin; Duchateau, Michel; Egedal, Carsten; Hackenberg, Wolfgang K. P.; Hippler, Stefan; Kellner, Stefan; van Kesteren, Arno; Koch, Franz; Neumann, Udo; Ott, Thomas; Quattri, Marco; Quentin, Jutta; Rabien, Sebastian; Tamai, Roberto; Tapia, Mario; Tarenghi, Massimo

    2003-02-01

    We report on the ongoing VLT Laser Guide Star Facility project, which will allow the ESO UT4 telescope to produce an artificial reference star for the Adaptive Optics systems NAOS-CONICA and SINFONI. A custom developed dye laser producing >10W CW at 589nm is installed on-board of the UT4 telescope, then relayed by means of a single mode optical fiber behind the secondary mirror, where a 500mm diameter lightweight, f/1 launch telescope is projecting the laser beam at 90 km altitude. We described the design tradeoffs and provide some details of the chosen subsystems. This paper is an update including subsystems results, to be read together with our previous paper on LGSF design description.

  19. Hubble Tarantula Treasury Project - IV. The extinction law

    Science.gov (United States)

    De Marchi, Guido; Panagia, Nino; Sabbi, Elena; Lennon, Daniel; Anderson, Jay; van der Marel, Roeland; Cignoni, Michele; Grebel, Eva K.; Larsen, Søren; Zaritsky, Dennis; Zeidler, Peter; Gouliermis, Dimitrios; Aloisi, Alessandra

    2016-02-01

    We report on the study of interstellar extinction across the Tarantula Nebula (30 Doradus), in the Large Magellanic Cloud, using observations from the Hubble Tarantula Treasury Project in the 0.3-1.6 μm range. The considerable and patchy extinction inside the nebula causes about 3500 red clump stars to be scattered along the reddening vector in the colour-magnitude diagrams, thereby allowing an accurate determination of the reddening slope in all bands. The measured slope of the reddening vector is remarkably steeper in all bands than in the the Galactic diffuse interstellar medium. At optical wavelengths, the larger ratio of total-to-selective extinction, namely RV = 4.5 ± 0.2, implies the presence of a grey component in the extinction law, due to a larger fraction of large grains. The extra large grains are most likely ices from supernova ejecta and will significantly alter the extinction properties of the region until they sublimate in 50-100 Myr. We discuss the implications of this extinction law for the Tarantula Nebula and in general for regions of massive star formation in galaxies. Our results suggest that fluxes of strongly star-forming regions are likely to be underestimated by a factor of about 2 in the optical.

  20. Periumbilical Pain with Radiation to Both Legs Following Tarantula Bite; a Case Report

    Directory of Open Access Journals (Sweden)

    Mahboob Pouraghaei

    2015-07-01

    Full Text Available Tarantulas have recently become as pets in most parts of the world that increased the probability of encountering emergency physicians with patients hurt with these spiders. Their attacks usually do not cause general manifestation, however there are some case reports in this regard. Here, a 40-year-old man was reported who was referred to the emergency department with severe periumbilical pain that radiated to both legs and diagnosed as a victim of tarantula bite. Such symptoms usually are belonging to other spiders like Black Widow spider, but it seems that tarantula can mimic them in some cases, too.

  1. Periumbilical Pain with Radiation to Both Legs Following Tarantula Bite; a Case Report.

    Science.gov (United States)

    Pouraghaei, Mahboob; Shams Vahdati, Samad; Mashhadi, Ibrahim; Mahmoudieh, Taranoom

    2015-01-01

    Tarantulas have recently become as pets in most parts of the world that increased the probability of encountering emergency physicians with patients hurt with these spiders. Their attacks usually do not cause general manifestation, however there are some case reports in this regard. Here, a 40-year-old man was reported who was referred to the emergency department with severe periumbilical pain that radiated to both legs and diagnosed as a victim of tarantula bite. Such symptoms usually are belonging to other spiders like Black Widow spider, but it seems that tarantula can mimic them in some cases, too.

  2. Flame Length

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — Flame length was modeled using FlamMap, an interagency fire behavior mapping and analysis program that computes potential fire behavior characteristics. The tool...

  3. Hubble Tarantula Treasury Project. IV. The extinction law

    CERN Document Server

    De Marchi, Guido; Sabbi, Elena; Lennon, Daniel; Anderson, Jay; van der Marel, Roeland; Cignoni, Michele; Grebel, Eva K; Larsen, Soeren; Zaritsky, Dennis; Zeidler, Peter; Gouliermis, Dimitrios; Aloisi, Alessandra

    2015-01-01

    We report on the study of interstellar extinction across the Tarantula nebula (30 Doradus), in the Large Magellanic Cloud, using observations from the Hubble Tarantula Treasury Project in the 0.3 - 1.6 micron range. The considerable and patchy extinction inside the nebula causes about 3500 red clump stars to be scattered along the reddening vector in the colour-magnitude diagrams, thereby allowing an accurate determination of the reddening slope in all bands. The measured slope of the reddening vector is remarkably steeper in all bands than in the the Galactic diffuse interstellar medium. At optical wavelengths, the larger ratio of total-to-selective extinction, namely Rv = 4.5 +/- 0.2, implies the presence of a grey component in the extinction law, due to a larger fraction of large grains. The extra large grains are most likely ices from supernova ejecta and will significantly alter the extinction properties of the region until they sublimate in 50 - 100 Myr. We discuss the implications of this extinction la...

  4. The Tarantula Festival: Joy and Distress in Upper Aragon

    Directory of Open Access Journals (Sweden)

    Tausiet, María

    2009-12-01

    Full Text Available Tarantism (a mythically-based, ritualized reaction to the bite of the dreaded tarantula in the belief that the victim could only be cured by music and dance had existed in Italy since time immemorial; yet it manifested itself also in Spain, where it has been far less studied, at least from the perspective of cultural history. Tarantism was certainly known in Aragon until well into the 20th century, as reported by informants in Fraga (Huesca who recall “The Tarantula Festival,” by which all forms of individual suffering were communally exorcised through the power of sympathy and neighbourly solidarity.

    El tarantismo (fenómeno mítico-ritual según el cual quienes eran picados por la temida tarántula sólo podían recuperarse mediante la música y el baile se manifestó desde antiguo en Italia, pero también en España, donde no ha sido tan estudiado, al menos desde la perspectiva de la historia cultural. De la vigencia de dicho fenómeno en Aragón hasta bien entrado el siglo XX dan cuenta las entrevistas en Fraga (Huesca con varios informantes acerca de la llamada “Fiesta de la Tarántula”: una forma comunitaria de exorcizar todo tipo de desgracias individuales, gracias al poder de la compasión y la solidaridad vecinal.

  5. VizieR Online Data Catalog: Hubble Tarantula Treasury Project (HTTP). III. (Sabbi+, 2016)

    Science.gov (United States)

    Sabbi, E.; Lennon, D. J.; Anderson, J.; Cignoni, M.; van der Marel, R. P.; Zaritsky, D.; de Marchi, G.; Panagia, N.; Gouliermis, D. A.; Grebel, E. K.; Gallagher, J. S., III; Smith, L. J.; Sana, H.; Aloisi, A.; Tosi, M.; Evans, C. J.; Arab, H.; Boyer, M.; de Mink, S. E.; Gordon, K.; Koekemoer, A. M.; Larsen, S. S.; Ryon, J. E.; Zeidler, P.

    2016-02-01

    Hubble Tarantula Treasury Project (HTTP; HST 12939, PI Elena Sabbi + HST 12499, PI Danny Lennon) was awarded 60 orbits of HST time in cycle 20 to survey the entire Tarantula Nebula (30 Doradus), using both the UVIS and the IR channels of the Wide Field Camera 3 (WFC3), and, in parallel, the Wide Field Channel (WFC) of the Advanced Camera for Surveys (ACS). See log of the observations (from 2011 Oct 03 to 2013 Sep 17) in table 1. (2 data files).

  6. The European Southern Observatory and VLT telescopes on Paranal

    Science.gov (United States)

    Boley, P. A.

    2012-01-01

    The Very Large Telescope (VLT) of the European Southern Observatory (ESO) on Cerro Paranal is one of the most influential observing complexes in the world. In this overview lecture, an introduction to the ESO organization and VLT telescopes is presented, along with a small selection of scientific works. Particular attention is given to the importance of the VLT for the Russian scientific community, as well as to present and future perspectives for making use of ESO and VLT data.

  7. The optical imaging of tarantula hair corneal injury: One case report and review of the literature.

    Science.gov (United States)

    Hu, Yuedong; Xu, Yuanyuan

    2017-09-01

    Tarantulas belonging to the Theraphosidae family are more and more popular as family pets. Ocular injuries caused by tarantulas are reported in several articles. We hereby report the first known case of ocular injury caused by a tarantula in China and observed by anterior segment optical coherence tomography (AS-OCT). A 22-year-old girl was referred to our hospital with one-week history of red and irritated left eye after she grabbed her molting Chilean Rose Tarantula. Her best-corrected visual acuity was 20/20 on both eyes. Her left eyelid was slightly red and edema. Slit-lamp examination found that more than a dozen of microscopic barbed hairs embedded into the cornea. AS-OCT showed that barbed hairs embedded in the cornea in different direction and the length of the hairs ranged from 173μm to 395μm. The anterior chamber was quiet with normal fundus and intraocular pressure. Topical steroid treatment was prescribed and the response was good. No corneal opacity or intraocular inflammation was observed after topical steroid treatment for one month. As exotic pets become more and more popular, the importance of wearing ocular protection when handling tarantulas should be emphasized when they are sold. Tarantulas are unsuitable pet for children. When a patient presents with an unusual red eye, pet-keeping history, spiders included, should be asked. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. When VLT Meets HST : The HUGS Survey

    NARCIS (Netherlands)

    Fontana, A.; Dunlop, J. S.; Paris, D.; Targett, T.; Boutsia, K.; Castellano, M.; Galametz, A.; Grazian, A.; McLure, R.; Merlin, E.; Pentericci, L.; Wuyts, S.; Almaini, O.; Caputi, K.; Chary, R.-R.; Cirasuolo, M.; Conselice, C.; Cooray, A.; Daddi, E.; Dickinson, M.; Faber, S. M.; Fazio, G.; Ferguson, H.; Giallongo, E.; Giavalisco, M.; Grogin, N.; Hathi, N.; Koekemoer, A.; Koo, D. C.; Lucas, R.; Nonino, M.; Rix, H.-W.; Renzini, A.; Rosario, D.; Santini, P.; Scarlata, C.; Sommariva, V.; Stark, D. P.; van der Wel, A.; Vanzella, E.; Wild, V.; Yan, H.; Zibetti, S.

    2014-01-01

    A new ultra-deep near-infrared imaging survey has been completed using the HAWK-I imager at the VLT. It is named HUGS (HAWK-I Ultra Deep Survey and GOODS Survey) and delivers the deepest, highest quality images ever collected in the K-band. HUGS complements the data delivered by the HST CANDELS surv

  9. VLT Data Flow System Begins Operation

    Science.gov (United States)

    1999-06-01

    Building a Terabyte Archive at the ESO Headquarters The ESO Very Large Telescope (VLT) is the sum of many sophisticated parts. The site at Cerro Paranal in the dry Atacama desert in Northern Chile is one of the best locations for astronomical observations from the surface of the Earth. Each of the four 8.2-m telescopes is a technological marvel with self-adjusting optics placed in a gigantic mechanical structure of the utmost precision, continuously controlled by advanced soft- and hardware. A multitude of extremely complex instruments with sensitive detectors capture the faint light from distant objects in the Universe and record the digital data fast and efficiently as images and spectra, with a minimum of induced noise. And now the next crucial link in this chain is in place. A few nights ago, following an extended test period, the VLT Data Flow System began providing the astronomers with a steady stream of high-quality, calibrated image and spectral data, ready to be interpreted. The VLT project has entered into a new phase with a larger degree of automation. Indeed, the first 8.2-m Unit Telescope, ANTU, with the FORS1 and ISAAC instruments, has now become a true astronomy machine . A smooth flow of data through the entire system ESO PR Photo 25a/99 ESO PR Photo 25a/99 [Preview - JPEG: 400 x 292 pix - 104k] [Normal - JPEG: 800 x 584 pix - 264k] [High-Res - JPEG: 3000 x 2189 pix - 1.5M] Caption to ESO PR Photo 25a/99 : Simplified flow diagramme for the VLT Data Flow System . It is a closed-loop software system which incorporates various subsystems that track the flow of data all the way from the submission of proposals to storage of the acquired data in the VLT Science Archive Facility. The DFS main components are: Program Handling, Observation Handling, Telescope Control System, Science Archive, Pipeline and Quality Control. Arrows indicate lines of feedback. Already from the start of this project more than ten years ago, the ESO Very Large Telescope was

  10. VLT imaging of the {\\beta} Pictoris gas disk

    CERN Document Server

    Nilsson, R; Olofsson, G; Fathi, K; Thébault, Ph; Liseau, R

    2012-01-01

    Circumstellar debris disks older than a few Myr should be largely devoid of primordial gas remaining from the protoplanetary disk phase. Tracing the origin of observed atomic gas in Keplerian rotation in the edge-on debris disk surrounding the ~12 Myr old star {\\beta} Pictoris requires more detailed information about its spatial distribution than has previously been acquired by limited slit spectroscopy. Especially indications of asymmetries and presence of Ca II gas at high disk latitudes call for additional investigation. We set out to recover a complete image of the Fe I and Ca II gas emission around {\\beta} Pic by spatially resolved, high-resolution spectroscopic observations to better understand the morphology and origin of the gaseous disk component. The multiple fiber facility FLAMES/GIRAFFE at the VLT, with the large IFU ARGUS, was used to obtain spatially resolved optical spectra in four regions covering the northeast and southwest side of the disk. Emission lines from Fe I and Ca II were mapped and ...

  11. MASSIVE STARS: FROM THE VLT TO THE ELT

    Directory of Open Access Journals (Sweden)

    Chris Evans

    2008-01-01

    Full Text Available Nuestro conocimiento de las estrellas masivas ha aumentado significativamente en los últimos 30 años gracias a las nuevas instalaciones y tecnologías. En esta contribución presento un gran survey de estrellas masivas que se ha realizado recientemente mediante el uso de VLT-FLAMES, mostrando los campos observados y remarcando la fracción de estrellas binarias que se ha encontrado. Estos datos se han utilizado para la primera comprobación empírica de la dependencia de la intensidad de los vientos estelares con la metalicidad, encontrándose un buen acuerdo con la teoría un resultado de gran importancia para los modelos de evolución estelar, que se utilizan para la interpretación de cúmulos lejanos, starburst y galaxias con formación estelar. Dando un paso más, comentaré como en la actualidad se están dedicando grandes esfuerzos al avance de los planes de actuación y desarrollo de los Telescopios de Gran Tamaño, que serán una realidad en un futuro próximo; este hecho nos ofrecerá una posibilidad más que interesante para obtener observaciones con resolución espacial de estrellas masivas más allá del Grupo Local.

  12. Flames High Resolution Spectroscopy of RGB Stars in the Carina Dwarf Spheroidal Galaxy

    NARCIS (Netherlands)

    Lemasle, B.; Hill, V.; Tolstoy, E.; Venn, K.

    2011-01-01

    Carina is a small and faint classical dwarf spheroidal galaxy in the halo of the Milky Way with a highly episodic star formation history (e.g., Hurley-Keller et al. 1998). Using VLT/FLAMES in high resolution mode, we significantly increase the sample of stars with abundance determinations in Carina,

  13. Flames in vortices & tulip-flame inversion

    Science.gov (United States)

    Dold, J. W.

    This article summarises two areas of research regarding the propagation of flames in flows which involve significant fluid-dynamical motion [1]-[3]. The major difference between the two is that in the first study the fluid motion is present before the arrival of any flame and remains unaffected by the flame [1, 2] while, in the second study it is the flame that is responsible for all of the fluid dynamical effects [3]. It is currently very difficult to study flame-motion in which the medium is both highly disturbed before the arrival of a flame and is further influenced by the passage of the flame.

  14. Progress on the VLT Adaptive Optics Facility

    Science.gov (United States)

    Arsenault, R.; Madec, P.-Y.; Paufique, J.; Ströbele, S.; Pirard, J.-F.; Vernet, É.; Hackenberg, W.; Hubin, N.; Jochum, L.; Kuntschner, H.; Glindemann, A.; Amico, P.; Lelouarn, M.; Kolb, J.; Tordo, S.; Donaldson, R.; Sã¶Nke, C.; Bonaccini Calia, D.; Conzelmann, R.; Delabre, B.; Kiekebusch, M.; Duhoux, P.; Guidolin, I.; Quattri, M.; Guzman, R.; Buzzoni, B.; Comin, M.; Dupuy, C.; Quentin, J.; Lizon, J.-L.; Silber, A.; Jolly, P.; Manescau, A.; Hammersley, P.; Reyes, J.; Jost, A.; Duchateau, M.; Heinz, V.; Bechet, C.; Stuik, R.

    2010-12-01

    The Very Large Telescope (VLT) Adaptive Optics Facility is a project that will transform one of the VLT's Unit Telescopes into an adaptive telescope that includes a deformable mirror in its optical train. For this purpose the secondary mirror is to be replaced by a thin shell deformable mirror; it will be possible to launch four laser guide stars from the centrepiece and two adaptive optics modules are being developed to feed the instruments HAWK-I and MUSE. These modules implement innovative correction modes for seeing improvement through ground layer adaptive optics and, for high Strehl ratio performance, laser tomography adaptive correction. The performance of these modes will be tested in Europe with a custom test bench called ASSIST. The project has completed its final design phase and concluded an intense phase of procurement; the year 2011 will see the beginning of assembly, integration and tests.

  15. ESO VLT laser guide star facility

    Science.gov (United States)

    Bonaccini, Domenico; Hackenberg, Wolfgang K.; Cullum, Martin J.; Brunetto, Enzo; Ott, Thomas; Quattri, Marco; Allaert, Eric; Dimmler, Martin; Tarenghi, Massimo; Van Kersteren, A.; Di Chirico, C.; Buzzoni, Bernard; Gray, Peter; Tamai, R.; Tapia, M.

    2002-02-01

    We report in this paper on the design and progress of the ESO Laser Guide Star Facility. The project will create a user facility embedded in UT4, to produce in the Earth's Mesosphere Laser Guide Stars, which extend the sky coverage of Adaptive Optics systems on the VLT UT4 telescope. Embedded into the project are provisions for multiple LGS to cope with second generation MCAO instruments.

  16. The Tarantula Massive Binary Monitoring. I. Observational campaign and OB-type spectroscopic binaries

    Science.gov (United States)

    Almeida, L. A.; Sana, H.; Taylor, W.; Barbá, R.; Bonanos, A. Z.; Crowther, P.; Damineli, A.; de Koter, A.; de Mink, S. E.; Evans, C. J.; Gieles, M.; Grin, N. J.; Hénault-Brunet, V.; Langer, N.; Lennon, D.; Lockwood, S.; Maíz Apellániz, J.; Moffat, A. F. J.; Neijssel, C.; Norman, C.; Ramírez-Agudelo, O. H.; Richardson, N. D.; Schootemeijer, A.; Shenar, T.; Soszyński, I.; Tramper, F.; Vink, J. S.

    2017-02-01

    Context. Massive binaries play a crucial role in the Universe. Knowing the distributions of their orbital parameters is important for a wide range of topics from stellar feedback to binary evolution channels and from the distribution of supernova types to gravitational wave progenitors, yet no direct measurements exist outside the Milky Way. Aims: The Tarantula Massive Binary Monitoring project was designed to help fill this gap by obtaining multi-epoch radial velocity (RV) monitoring of 102 massive binaries in the 30 Doradus region. Methods: In this paper we analyze 32 FLAMES/GIRAFFE observations of 93 O- and 7 B-type binaries. We performed a Fourier analysis and obtained orbital solutions for 82 systems: 51 single-lined (SB1) and 31 double-lined (SB2) spectroscopic binaries. Results: Overall, the binary fraction and orbital properties across the 30 Doradus region are found to be similar to existing Galactic samples. This indicates that within these domains environmental effects are of second order in shaping the properties of massive binary systems. A small difference is found in the distribution of orbital periods, which is slightly flatter (in log space) in 30 Doradus than in the Galaxy, although this may be compatible within error estimates and differences in the fitting methodology. Also, orbital periods in 30 Doradus can be as short as 1.1 d, somewhat shorter than seen in Galactic samples. Equal mass binaries (q> 0.95) in 30 Doradus are all found outside NGC 2070, the central association that surrounds R136a, the very young and massive cluster at 30 Doradus's core. Most of the differences, albeit small, are compatible with expectations from binary evolution. One outstanding exception, however, is the fact that earlier spectral types (O2-O7) tend to have shorter orbital periods than later spectral types (O9.2-O9.7). Conclusions: Our results point to a relative universality of the incidence rate of massive binaries and their orbital properties in the

  17. Effects of Tarantula cubensis D6 on aflatoxin-induced injury in biochemical parameters in rats.

    Science.gov (United States)

    Karabacak, Mürsel; Eraslan, Gökhan; Kanbur, Murat; Sarıca, Zeynep Soyer

    2015-07-01

    Aflatoxins are toxic fungal metabolites that have adverse effects on humans and animals. Tarantula cubensis D6 is used as a homeopathic medicine for different purposes. The present study investigates the effects of Tarantula cubensis D6 on the oxidant-antioxidant balance and some biochemical parameters against exposure to aflatoxin. Thirty-two Sprague-Dawley female rats were used and evenly divided into four groups. Group 1 served as control. Groups 2, 3, and 4 received 200 μl/kg.bw/day Tarantula cubensis D6 (applied subcutaneously), 400 μg/kg.bw/day total aflatoxin (approximately 80% AF B1, 10% AF B2, 6 %AF G1, and 4% AF G2), and 200 μl/kg.bw/day Tarantula cubensis D6 plus 400 μg/kg.bw/day total aflatoxin, respectively, for 28 days. At the end of 28 days, blood samples and some organs (liver, kidney, brain, and spleen) were taken from all the animals. Oxidative stress markers (MDA, SOD, CAT, GSH-Px) and some biochemical parameters (glucose, triglyceride, cholesterol, BUN, creatinine, AST, ALT and ALP, total protein, albumin) were evaluated in blood samples and tissues. Aflatoxin caused negative changes in all oxidative stress parameters and some biochemical parameters (glucose, triglyceride, cholesterol, creatinine, AST, ALT, ALP, total protein, albumin). Administration of Tarantula cubensis D6 partly alleviated aflatoxin-induced negative changes. Our results indicated that Tarantula cubensis D6 partially neutralized the deleterious effects of aflatoxin. Copyright © 2015 The Faculty of Homeopathy. Published by Elsevier Ltd. All rights reserved.

  18. VLT/SINFONI spectroscopy of the superantennae

    Directory of Open Access Journals (Sweden)

    J. Reunanen

    2007-01-01

    Full Text Available Presentamos los resultados de espectroscopia de campo integral en bandas H y K VLT/SINFONI de IRAS 19254-7245 (Superantennae, una ULRIG cercana con un AGN embebido. Los mapas de las líneas, campos de velocidades y mapas de dispersión de velocidades se presentan para varias líneas de emisión. Las proporciones de las líneas de emisión de H2 son consistentes con la excitación térmica, debida probablemente a choques.

  19. Data Flow System for the VLT Interferometer

    Science.gov (United States)

    Ballester, P.; Licha, T.; Percheron, I.; Sabet, C.

    2006-07-01

    A milestone on the accuracy of angular measurements is reached with each new instrument on the VLT interferometer: about 10 milliarcsec for MIDI (N Band), 1 milliarcsec for AMBER (JHK bands) and, later, the ultimate goal of 10 microarcsec for the PRIMA imaging and astrometry facility. Extracting the science information from these measurements requires a unified understanding of the data obtained by modelling, homogeneous calibration of large datasets and robust data reduction methods. We describe in this poster the operational tools provided for observation preparation, pipeline processing, and data quality control.

  20. ESO-VLT Science Data Processing

    Science.gov (United States)

    Hanuschik, Reinhard; Data Processing; Quality Control Group

    2017-09-01

    "In the past three years the QC group at ESO has installed an efficient process to create science-grade data products from VLT instruments. With the focus on spectroscopic observations, these data products are complementary to the (externally provided) data products from the surveys. The production line combines efficient mass production (more than one million spectra have been generated so far), previews, and quality control. All data products are available to the community through the ESO archive interface. The talk will highlight the most recent addition, the MUSE datacubes."

  1. Beam combination modes of the VLT

    Science.gov (United States)

    Merkle, Fritz

    The optical configuration of the ESO Very Large Telescope (VLT) is based on a linear array of 4 independently mounted 8-m telescopes. This concept allows a flexible and versatile use of the telescopes. They can be operated either independently or in various combination schemes. In the latter case, the light collected with the unit telescopes is fed via beam combination optics to the combined focus. The incoherent combination with a combined coude focus offers the light collecting power approximately equivalent to a 16-m single dish telescope. The efficiency of the combined foci operation is only given if the losses in the combining train are minimized.

  2. With the VLT Interferometer towards Sharper Vision

    Science.gov (United States)

    2000-05-01

    The Nova-ESO VLTI Expertise Centre Opens in Leiden (The Netherlands) European science and technology will gain further strength when the new, front-line Nova-ESO VLTI Expertise Centre (NEVEC) opens in Leiden (The Netherlands) this week. It is a joint venture of the Netherlands Research School for Astronomy (NOVA) (itself a collaboration between the Universities of Amsterdam, Groningen, Leiden, and Utrecht) and the European Southern Observatory (ESO). It is concerned with the Very Large Telescope Interferometer (VLTI). The Inauguration of the new Centre will take place on Friday, May 26, 2000, at the Gorlaeus Laboratory (Lecture Hall no. 1), Einsteinweg 55 2333 CC Leiden; the programme is available on the web. Media representatives who would like to participate in this event and who want further details should contact the Nova Information Centre (e-mail: jacques@astro.uva.nl; Tel: +31-20-5257480 or +31-6-246 525 46). The inaugural ceremony is preceded by a scientific workshop on ground and space-based optical interferometry. NEVEC: A Technology Centre of Excellence As a joint project of NOVA and ESO, NEVEC will develop in the coming years the expertise to exploit the unique interferometric possibilities of the Very Large Telescope (VLT) - now being built on Paranal mountain in Chile. Its primary goals are the * development of instrument modeling, data reduction and calibration techniques for the VLTI; * accumulation of expertise relevant for second-generation VLTI instruments; and * education in the use of the VLTI and related matters. NEVEC will develop optical equipment, simulations and software to enable interferometry with VLT [1]. The new Center provides a strong impulse to Dutch participation in the VLTI. With direct involvement in this R&D work, the scientists at NOVA will be in the front row to do observations with this unique research facility, bound to produce top-level research and many exciting new discoveries. The ESO VLTI at Paranal ESO PR Photo 14a/00

  3. Obsolescence of electronics at the VLT

    Science.gov (United States)

    Hüdepohl, Gerhard; Haddad, Juan-Pablo; Lucuix, Christian

    2016-07-01

    The ESO Very Large Telescope Observatory (VLT) at Cerro Paranal in Chile had its first light in 1998. Most of the telescopes' electronics components were chosen and designed in the mid 1990s and are now around 20 years old. As a consequence we are confronted with increasing failure rates due to aging and lack of spare parts, since many of the components are no longer available on the market. The lifetime of large telescopes is generally much beyond 25 years. Therefore the obsolescence of electronics components and modules becomes an issue sooner or later and forces the operations teams to upgrade the systems to new technology in order to avoid that the telescope becomes inoperable. Technology upgrade is a time and money consuming process, which in many cases is not straightforward and has various types of complications. This paper shows the strategy, analysis, approach, timeline, complications and progress in obsolescence driven electronics upgrades at the ESO Very Large Telescope (VLT) at the Paranal Observatory.

  4. VLT Unit Telescopes Named at Paranal Inauguration

    Science.gov (United States)

    1999-03-01

    This has been a busy, but also a very successful and rewarding week for the European Southern Observatory and its staff. While "First Light" was achieved at the second 8.2-m VLT Unit Telescope (UT2) ahead of schedule, UT1 produced its sharpest image so far. This happened at a moment of exceptional observing conditions in the night between March 4 and 5, 1999. During a 6-min exposure of the majestic spiral galaxy, NGC 2997 , stellar images of only 0.25 arcsec FWHM (full-width half-maximum) were recorded. This and two other frames of nearly the same quality have provided the base for the beautiful colour-composite shown above. At this excellent angular resolution, individual star forming regions are well visible along the spiral arms. Of particular interest is the peculiar, twisted shape of the long spiral arm to the right. The Paranal Inauguration The official inauguration of the Paranal Observatory took place in the afternoon of March 5, 1999, in the presence of His Excellency, the President of the Republic of Chile, Don Eduardo Frei Ruiz-Tagle, and ministers of his cabinet, as well the Ambassadors to Chile of the ESO member states and many other distinguished guests. The President of the ESO Council, Mr. Henrik Grage, and the ESO Director General, Professor Riccardo Giacconi, were the foremost representatives of the ESO organisation; most members of the ESO Council and ESO staff also participated. A substantial number of media representatives from Europe and Chile were present and reported - often live - from Paranal during the afternoon and evening. The guests were shown the impressive installations at the new observatory, including the first and second 8.2-m VLT Unit Telescopes; the latter having achieved "First Light" just four days before. A festive ceremony took place in the dome of UT2, under the large telescope structure that had been tilted towards the horizon to make place for the numerous participants. After an introductory address by the ESO Director

  5. RADIAL VELOCITIES FROM VLT-KMOS SPECTRA OF GIANT STARS IN THE GLOBULAR CLUSTER NGC 6388

    Energy Technology Data Exchange (ETDEWEB)

    Lapenna, E.; Mucciarelli, A.; Lanzoni, B.; Ferraro, F. R.; Dalessandro, E. [Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy); Origlia, L. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani, 1, I-40127 Bologna (Italy); Valenti, E. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München (Germany); Cirasuolo, M. [Institute for Astronomy, University of Edinburgh and STFC, UK Astronomy Technology Center Royal Observatory, Blackford Hill, EH9 3HJ, Edinburgh (United Kingdom)

    2015-01-01

    We present new radial velocity measurements for 82 stars, members of the Galactic globular cluster (GC) NGC 6388, obtained from ESO-VLT K-band Multi Object Spectrograph (KMOS) spectra acquired during the instrument Science Verification. The accuracy of the wavelength calibration is discussed and a number of tests of the KMOS response are presented. The cluster systemic velocity obtained (81.3 ± 1.5 km s{sup –1}) is in very good agreement with previous determinations. While a hint of ordered rotation is found between 9'' and 20'' from the cluster center, where the distribution of radial velocities is clearly bimodal, more data are needed before drawing any firm conclusions. The acquired sample of radial velocities has also been used to determine the cluster velocity dispersion (VD) profile between ∼9'' and 70'', supplementing previous measurements at r < 2'' and r > 60'' obtained with ESO-SINFONI and ESO-FLAMES spectroscopy, respectively. The new portion of the VD profile nicely matches the previous ones, better defining the knee of the distribution. The present work clearly shows the effectiveness of a deployable integral field unit in measuring the radial velocities of individual stars for determining the VD profile of Galactic GCs. It represents the pilot project for an ongoing large program with KMOS and FLAMES at the ESO-VLT, aimed at determining the next generation of VD and rotation profiles for a representative sample of GCs.

  6. Chemically mediated burrow recognition in the Mexican tarantula Brachypelma vagans female

    Science.gov (United States)

    Dor, Ariane; Machkour-M'rabet, Salima; Legal, Luc; Williams, Trevor; Hénaut, Yann

    2008-12-01

    Chemically mediated communication is common in spiders but has been poorly studied in burrowing tarantulas. This study aimed to determine whether chemical cues influence the behaviour of females of Brachypelma vagans, a Mexican species of tarantula, during encounters with previously inhabited burrows or with extracts from the silk of conspecific females. In laboratory choice tests, female tarantulas entered a burrow that had previously been inhabited by a conspecific female significantly more frequently than a burrow that had never been inhabited. The identity of the previous inhabitant also affected the number of spiders that chose to enter a burrow. Spiders were quicker to choose and enter a burrow previously inhabited by themselves than a burrow previously inhabited by a conspecific or a burrow that had not been previously inhabited. Hexane, methanol and dichloromethane extracts of conspecific silk elicited different responses from female tarantulas when extracts were placed on filter paper disks at one end of an experimental arena with a control filter paper disk, on to which the corresponding solvent alone had been pipetted, placed on the other end of the arena. Spiders showed the strongest responses to hexane extracts of silk, with a significant preference to move towards the hexane extract and a significantly greater period of time spent in proximity to the hexane extract compared to the control disk. Overall and in contrast to expectations, tarantulas were most strongly attracted to the cues left by other conspecific females. As encounters between B. vagans females usually lead to aggression and mortality of one of the participants, we conclude that chemical cues are not signals that are deliberately released by burrow-inhabiting females but may inadvertently escape and cannot be easily suppressed.

  7. Lipoprotein-induced phenoloxidase-activity in tarantula hemocyanin.

    Science.gov (United States)

    Schenk, Sven; Schmidt, Juliane; Hoeger, Ulrich; Decker, Heinz

    2015-08-01

    Phenoloxidases play vital roles in invertebrate innate immune reactions, wound closure and sclerotization processes in arthropods. In chelicerates, where phenoloxidases are lacking, phenoloxidase-activity can be induced in the oxygen carrier hemocyanin in vitro by proteolytic cleavage, incubation with the artificial inducer SDS, or lipids. The role of protein-protein interaction has up to now received little attention. This is remarkable, as lipoproteins - complexes of proteins and lipids - are present at high concentrations in arthropod hemolymph. We characterized the three lipoproteins present in tarantula hemolymph, two high-density lipoproteins and one very high-density lipoprotein, and show that the two high-density lipoproteins have distinct structures: the more abundant high-density lipoprotein is an ellipsoid particle with axes of ~22.5 nm and ~16.8 nm, respectively. The second high-density lipoprotein, present only in trace amount, is a large discoidal lipoprotein with a diameter of ~38.4 nm and an on-edge thickness of ~7.1 nm. We further demonstrate that the interaction between lipoproteins and hemocyanin induces phenoloxidase activity in hemocyanin, and propose that this activation is due to protein-protein interaction rather than protein-lipid interaction, as neither lipid micelles nor lipid monomers were found to be activating. Activation was strongest in the presence of high-density lipoproteins; very high-density lipoproteins were found to be non-activating. This is the first time that the ability of lipoproteins to induce phenoloxidase activity of hemocyanin has been demonstrated, thus adding novel aspects to the function of lipoproteins apart from their known role in nutrient supply. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. SCIENCE OPPORTUNITIES ON THE VLT INTERFEROMETER

    Directory of Open Access Journals (Sweden)

    M. Schöller

    2010-01-01

    Full Text Available El interferómetro del VLT está desde hace varios años en operaciones científicas, con nuevas oportunidades disponibles cada vez que nuevas instalaciones están siendo integradas. La mayor parte de estos pasos son fácilmente visibles, pero algunas posibilidades se presentan a partir de mejoras simples. Detallo el potencial científico del VLTI, dando una descripción de la infraestructura y los modos ofrecidos por los instrumentos. Luego examino las limitaciones fijadas por la accesibilidad del cielo, flujo del objeto en el espectro visible e infrarrojo, o la morfología del objeto, seguida por una discusión de qué información se puede extraer de las mediciones del VLTI. Finalizo con una perspectiva en las mejoras futuras del VLTI.

  9. "First Light" for the VLT Interferometer

    Science.gov (United States)

    2001-03-01

    Excellent Fringes From Bright Stars Prove VLTI Concept Summary Following the "First Light" for the fourth of the 8.2-m telescopes of the VLT Observatory on Paranal in September 2000, ESO scientists and engineers have just successfully accomplished the next major step of this large project. On March 17, 2001, "First Fringes" were obtained with the VLT Interferometer (VLTI) - this important event corresponds to the "First Light" for an astronomical telescope. At the VLTI, it occurred when the infrared light from the bright star Sirius was captured by two small telescopes and the two beams were successfully combined in the subterranean Interferometric Laboratory to form the typical pattern of dark and bright lines known as " interferometric fringes ". This proves the success of the robust VLTI concept, in particular of the "Delay Line". On the next night, the VLTI was used to perform a scientific measurement of the angular diameter of another comparatively bright star, Alpha Hydrae ( Alphard ); it was found to be 0.00929±0.00017 arcsec . This corresponds to the angular distance between the two headlights of a car as seen from a distance of approx. 35,000 kilometres. The excellent result was obtained during a series of observations, each lasting 2 minutes, and fully confirming the impressive predicted abilities of the VLTI . This first observation with the VLTI is a monumental technological achievement, especially in terms of accuracy and stability . It crucially depends on the proper combination and functioning of a large number of individual opto-mechnical and electronic elements. This includes the test telescopes that capture the starlight, continuous and extremely precise adjustment of the various mirrors that deflect the light beams as well as the automatic positioning and motion of the Delay Line carriages and, not least, the optimal tuning of the VLT INterferometer Commissionning Instrument (VINCI). These initial observations prove the overall concept for the

  10. VLT imaging of the β Pictoris gas disk

    Science.gov (United States)

    Nilsson, R.; Brandeker, A.; Olofsson, G.; Fathi, K.; Thébault, Ph.; Liseau, R.

    2012-08-01

    Context. Circumstellar debris disks older than a few Myr should be largely devoid of primordial gas remaining from the protoplanetary disk phase. Tracing the origin of observed atomic gas in Keplerian rotation in the edge-on debris disk surrounding the ~12 Myr old star β Pictoris requires more detailed information about its spatial distribution than has previously been acquired by limited slit spectroscopy. Especially indications of asymmetries and presence of Ca ii gas at high disk latitudes call for additional investigation to exclude or confirm its connection to observed dust structures or suggested cometary bodies on inclined eccentric orbits. Aims: We set out to recover a complete image of the Fe i and Ca ii gas emission around β Pic by spatially resolved, high-resolution spectroscopic observations to better understand the morphology and origin of the gaseous disk component. Methods: The multiple fiber facility FLAMES/GIRAFFE at the Very Large Telescope (VLT), with the large integral-field-unit ARGUS, was used to obtain spatially resolved optical spectra (from 385.9 to 404.8 nm) in four regions covering the northeast and southwest side of the disk. Emission lines from Fe i (at 386.0 nm) and Ca ii (at 393.4 and 396.8 nm) were mapped and could be used to fit a parametric function for the disk gas distribution, using a gas-ionisation code for gas-poor debris disks. Results: Both Fe i and Ca ii emission are clearly detected, with the former dominating along the disk midplane, and the latter revealing vertically more extended gas. The surface intensity of the Fe i emission is lower but more extended in the northeast (reaching the 210 AU limit of our observations) than in the southwest, while Ca ii shows the opposite asymmetry. The modelled Fe gas disk profile shows a linear increase in scale height with radius, and a vertical profile that suggests dynamical interaction with the dust. We also qualitatively demonstrate that the Ca ii emission profile can be

  11. Explosive Model Tarantula V1/JWL++ Calibration of LX-17: #2

    Energy Technology Data Exchange (ETDEWEB)

    Souers, P C; Vitello, P

    2009-05-01

    Tarantula V1 is a kinetic package for reactive flow codes that seeks to describe initiation, failure, dead zones and detonation simultaneously. The most important parameter is P1, the pressure between the initiation and failure regions. Both dead zone formation and failure can be largely controlled with this knob. However, V1 does failure with low settings and dead zones with higher settings, so that it cannot fulfill its purpose in the current format. To this end, V2 is under test. The derivation of the initiation threshold P0 is discussed. The derivation of the initiation pressure-tau curve as an output of Tarantula shows that the initiation package is sound. A desensitization package is also considered.

  12. The design of ERIS for the VLT

    Science.gov (United States)

    Amico, P.; Marchetti, E.; Pedichini, F.; Baruffolo, A.; Delabre, B.; Duchateau, M.; Ekinci, M.; Fantinel, D.; Fedrigo, E.; Finger, G.; Frank, C.; Hofmann, R.; Jolley, P.; Lizon, J. L.; Le Louarn, M.; Madec, P.-Y.; Soenke, C.; Weisz, H.

    2012-09-01

    The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation instrument planned for the Very Large Telescope (VLT) and the Adaptive Optics Facility (AOF)1. It is an AO assisted instrument that will make use of the Deformable Secondary Mirror and the new Laser Guide Star Facility (4LGSF), and it is designed for the Cassegrain focus of the telescope UT4. The project just concluded its conceptual design phase and is awaiting formal approval to continue to the next phase. ERIS will offer 1-5 μm imaging and 1-2.5 μm integral field spectroscopic capabilities with high Strehl performance. As such it will replace, with much improved single conjugated AO correction, the most scientifically important and popular observing capabilities currently offered by NACO2 (diffraction limited imaging in JM band, Sparse Aperture Masking and APP coronagraphy) and by SINFONI3, whose instrumental module, SPIFFI, will be re-used in ERIS. The Cassegrain location and the performance requirements impose challenging demands on the project, from opto-mechanical design to cryogenics to the operational concept. In this paper we describe the baseline design proposed for ERIS and discuss these technical challenges, with particular emphasis on the trade-offs and the novel solutions proposed for building ERIS.

  13. VLT spectroscopy of NGC3115 globular clusters

    CERN Document Server

    Kuntschner, H; Sharples, R M; Worthey, G; Fricke, K J; Kuntschner, Harald; Ziegler, Bodo L.; Worthey, Guy; Fricke, Klaus J.

    2002-01-01

    We present results derived from VLT-FORS2 spectra of 24 different globular clusters associated with the lenticular galaxy NGC3115. A subsample of 17 globular clusters have sufficiently high signal-to-noise to allow precision measurements of absorption line-strengths. Comparing these indices to new stellar population models by Thomas et al. we determine ages, metallicities and element abundance ratios. Our data are also compared with the Lick/IDS observations of Milky Way and M31 globular clusters. Unpublished higher order Balmer lines (HgammaA,F and HdeltaA,F) from the Lick/IDS observations are given in the Appendix. Our best age estimates show that the observed clusters which sample the bimodal colour distribution of NGC3115 are coeval within our observational errors (2-3 Gyr). Our best calibrated age/metallicity diagnostic diagram (Hbeta vs [MgFe]) indicates an absolute age of 11-12 Gyr. We confirm with our accurate line-strength measurements that the (V-I) colour is a good metallicity indicator within the ...

  14. Flame structure of methane inverse diffusion flame

    KAUST Repository

    Elbaz, Ayman M.

    2014-07-01

    This paper presents high speed images of OH-PLIF at 10. kHz simultaneously with 2D PIV (particle image velocimetry) measurements collected along the entire length of an inverse diffusion flame with circumferentially arranged methane fuel jets. For a fixed fuel flow rate, the central air jet Re was varied, leading to four air to fuel velocity ratios, namely Vr = 20.7, 29, 37.4 and 49.8. A double flame structure could be observed composed of a lower fuel entrainment region and an upper mixing and intense combustion region. The entrainment region was enveloped by an early OH layer, and then merged through a very thin OH neck to an annular OH layer located at the shear layer of the air jet. The two branches of this annular OH layer broaden as they moved downstream and eventfully merged together. Three types of events were observed common to all flames: breaks, closures and growing kernels. In upstream regions of the flames, the breaks were counterbalanced by flame closures. These breaks in OH signal were found to occur at locations where locally high velocity flows were impinging on the flame. As the Vr increased to 37.4, the OH layers became discontinuous over the downstream region of the flame, and these regions of low or no OH moved upstream. With further increases in Vr, these OH pockets act as flame kernels, growing as they moved downstream, and became the main mechanism for flame re-ignition. Along the flame length, the direction of the two dimensional principle compressive strain rate axis exhibited a preferred orientation of approximately 45° with respect to the flow direction. Moreover, the OH zones were associated with elongated regions of high vorticity. © 2013 Elsevier Inc.

  15. The effects of Tarantula cubensis venom on open wound healing in rats.

    Science.gov (United States)

    Gul Satar, N Y; Cangul, I T; Topal, A; Kurt, H; Ipek, V; Onel, G I

    2017-02-02

    The aim of this study was to evaluate the clinical and histopathological effects of two different dosages of alcohol extract of Tarantula cubensis (Theranekron) on open wounds. A total of 24 Sprague-Dawley rats were randomly divided into Tarantula cubensis extract (TCE1, n=8) 1/10 diluted, TCE (TCE2, n=8), and (3) vehicle-control (0.2 ml of 96 % ethanol, n=8) groups. Experimental full-thickness 1 x 1cm wounds were created on dorsum skin. TCE or vehicle were given systemically by subcutaneous injections on postoperative days 1 and 4. Wound planimetry and procurement of biopsies was performed on days 4, 8, 12 and 16. The mean non-epithelialised wound area in the vehicle-control group was significantly larger than in the TCE1 group on days 4, 8, 12 and 16, and in the TCE2 group on days 8, 12 and 16 (pwound contraction was significantly higher in the TCE1 and TCE2 groups than in the vehicle control group on days 8, 12 and 16 (pwound healing was characterised by a significant decrease in the neutrophil counts and a significant increase in neovascularisation; neither were effected by TCE. Our results suggest that alcohol extract of Tarantula cubensis accelerates epithelialisation and, thus, has beneficial effects on open wound healing in rats.

  16. VIMOS - a Cosmology Machine for the VLT

    Science.gov (United States)

    2002-03-01

    Successful Test Observations With Powerful New Instrument at Paranal [1] Summary One of the most fundamental tasks of modern astrophysics is the study of the evolution of the Universe . This is a daunting undertaking that requires extensive observations of large samples of objects in order to produce reasonably detailed maps of the distribution of galaxies in the Universe and to perform statistical analysis. Much effort is now being put into mapping the relatively nearby space and thereby to learn how the Universe looks today . But to study its evolution, we must compare this with how it looked when it still was young . This is possible, because astronomers can "look back in time" by studying remote objects - the larger their distance, the longer the light we now observe has been underway to us, and the longer is thus the corresponding "look-back time". This may sound easy, but it is not. Very distant objects are very dim and can only be observed with large telescopes. Looking at one object at a time would make such a study extremely time-consuming and, in practical terms, impossible. To do it anyhow, we need the largest possible telescope with a highly specialised, exceedingly sensitive instrument that is able to observe a very large number of (faint) objects in the remote universe simultaneously . The VLT VIsible Multi-Object Spectrograph (VIMOS) is such an instrument. It can obtain many hundreds of spectra of individual galaxies in the shortest possible time; in fact, in one special observing mode, up to 6400 spectra of the galaxies in a remote cluster during a single exposure, augmenting the data gathering power of the telescope by the same proportion. This marvellous science machine has just been installed at the 8.2-m MELIPAL telescope, the third unit of the Very Large Telescope (VLT) at the ESO Paranal Observatory. A main task will be to carry out 3-dimensional mapping of the distant Universe from which we can learn its large-scale structure . "First light

  17. Candle flames in microgravity

    Science.gov (United States)

    Dietrich, D. L.; Ross, H. D.; Tien, J. S.

    1995-01-01

    The candle flame in both normal and microgravity is non-propagating. In microgravity, however, the candle flame is also non-convective where (excepting Stefan flow) pure diffusion is the only transport mode. It also shares many characteristics with another classical problem, that of isolated droplet combustion. Given their qualitatively similar flame shapes and the required heat feedback to condensed-phase fuels, the gas-phase flow and temperature fields should be relatively similar for a droplet and a candle in reduced gravity. Unless the droplet diameter is maintained somehow through non-intrusive replenishment of fuel, the quasi-steady burning characteristics of a droplet can be maintained for only a few seconds. In contrast, the candle flame in microgravity may achieve a nearly steady state over a much longer time and is therefore ideal for examining a number of combustion-related phenomena. In this paper, we examine candle flame behavior in both short-duration and long-duration, quiescent, microgravity environments. Interest in this type of flame, especially 'candle flames in weightlessness', is demonstrated by very frequent public inquiries. The question is usually posed as 'will a candle flame burn in zero gravity', or, 'will a candle burn indefinitely (or steadily) in zero gravity in a large volume of quiescent air'. Intuitive speculation suggests to some that, in the absence of buoyancy, the accumulation of products in the vicinity of the flame will cause flame extinction. The classical theory for droplet combustion with its spherically-shaped diffusion flame, however, shows that steady combustion is possible in the absence of buoyancy if the chemical kinetics are fast enough. Previous experimental studies of candle flames in reduced and microgravity environments showed the flame could survive for at least 5 seconds, but did not reach a steady state in the available test time.

  18. VLT/VLTI Second-Generation Instrumentation: Lessons Learned

    Science.gov (United States)

    Gilmozzi, R.; Pasquini, L.; Russell, A.

    2016-12-01

    The five second-generation instruments already delivered for the Very Large Telescope (VLT) represent worthy successors to the first generation of instrumentation development. Despite this success, it is still possible to learn many lessons for the future. A review, preceded by a workshop, on the lessons learned from the second-generation instrumentation for the VLT and VLT Interferometer took place in November 2015, following a previous review twelve years ago on lessons learned from the first-generation instruments. The aim of the workshop was to identify lessons in order to help define/refine good practice and make recommendations for the future. This article briefly reports on the workshop and summarises the findings of the review panel, their recommendations and some of the steps to implement them.

  19. The 8.2 metre primary mirrors of the VLT

    Science.gov (United States)

    Dierickx, P.; Enard, D.; Merkle, F.; Noethe, L.; Wilson, R. N.

    1990-08-01

    The Very Large Telescope (VLT) presently being developed at ESO is described in terms of technological advances which make its use both technically effective and feasible. The VLT capitalizes on advances in materials, polishing techniques, and mirror support systems. The VLT consists of four 8-m alt-az telescopes and a 2-m auxiliary telescope in a single-dish configuration with Zerodur meniscus mirrors passively supported on a lateral system. A discussion of the tradeoffs between glass and metal mirrors is presented, and computerized polishing is described in relation to optical specifications. The mirror is supported with 150 axial and 60 lateral supports with electromechanical actuators to modulate applied force. The active optics concept is employed via the flexibility of the primary mirror, which generates elastomechanical deformations and the position and orientation of the secondary mirror.

  20. Flame Holder System

    Science.gov (United States)

    Haskin, Henry H. (Inventor); Vasquez, Peter (Inventor)

    2013-01-01

    A flame holder system includes a modified torch body and a ceramic flame holder. Catch pin(s) are coupled to and extend radially out from the torch body. The ceramic flame holder has groove(s) formed in its inner wall that correspond in number and positioning to the catch pin(s). Each groove starts at one end of the flame holder and can be shaped to define at least two 90.degree.turns. Each groove is sized to receive one catch pin therein when the flame holder is fitted over the end of the torch body. The flame holder is then manipulated until the catch pin(s) butt up against the end of the groove(s).

  1. Applications of Tunable Imaging Filters for the VLT

    CERN Document Server

    Jones, H

    2001-01-01

    Tunable imaging filters have been used for a variety of science programmes on the Anglo-Australian and William Herschel Telescopes during the last five years. This contribution describes these novel devices and reviews the science (both Galactic and extragalactic) done with them. Possible strategies for implementing a tunable filter at the VLT are also discussed. Significant scientific potential exists for a tunable filter on the VLT, particularly in the years before such capability becomes available on 8 -- 10 m-class telescopes elsewhere.

  2. Hubble and ESO's VLT provide unique 3D views of remote galaxies

    Science.gov (United States)

    2009-03-01

    Astronomers have obtained exceptional 3D views of distant galaxies, seen when the Universe was half its current age, by combining the twin strengths of the NASA/ESA Hubble Space Telescope's acute eye, and the capacity of ESO's Very Large Telescope to probe the motions of gas in tiny objects. By looking at this unique "history book" of our Universe, at an epoch when the Sun and the Earth did not yet exist, scientists hope to solve the puzzle of how galaxies formed in the remote past. ESO PR Photo 10a/09 A 3D view of remote galaxies ESO PR Photo 10b/09 Measuring motions in 3 distant galaxies ESO PR Video 10a/09 Galaxies in collision For decades, distant galaxies that emitted their light six billion years ago were no more than small specks of light on the sky. With the launch of the Hubble Space Telescope in the early 1990s, astronomers were able to scrutinise the structure of distant galaxies in some detail for the first time. Under the superb skies of Paranal, the VLT's FLAMES/GIRAFFE spectrograph (ESO 13/02) -- which obtains simultaneous spectra from small areas of extended objects -- can now also resolve the motions of the gas in these distant galaxies (ESO 10/06). "This unique combination of Hubble and the VLT allows us to model distant galaxies almost as nicely as we can close ones," says François Hammer, who led the team. "In effect, FLAMES/GIRAFFE now allows us to measure the velocity of the gas at various locations in these objects. This means that we can see how the gas is moving, which provides us with a three-dimensional view of galaxies halfway across the Universe." The team has undertaken the Herculean task of reconstituting the history of about one hundred remote galaxies that have been observed with both Hubble and GIRAFFE on the VLT. The first results are coming in and have already provided useful insights for three galaxies. In one galaxy, GIRAFFE revealed a region full of ionised gas, that is, hot gas composed of atoms that have been stripped of

  3. The sale of tarantulas in Cambodia for food or medicine: is it sustainable?

    Directory of Open Access Journals (Sweden)

    A.L. Yen

    2013-01-01

    Full Text Available The sale of tarantulas for either human consumption or for preparation of medicines has become more widespread in Cambodia over the last 10-20 years. With increased media exposure, the trade seems to be increasing, but there are serious questions as to its sustainability because of possible over-collecting of the spiders and also loss of habitats. This note outlines some of the fundamental questions that need to be addressed if this spider trade is to be sustainable or else we could see the loss of an important link in the forest food chain.

  4. SPHERE: A Planet Finder Instrument for the VLT

    NARCIS (Netherlands)

    Beuzit, J.L.; Feldt, M.; Dohlen, K.; Mouillet, D.; Puget, P.; Antichi, J.; Baudoz, P.; Boccaletti, A.; Carbillet, M.; Charton, J.; Claudi, R.; Fusco, T.; Gratton, R.; Henning, T.; Hubin, N.; Joos, F.; Kasper, M.; Langlois, M.; Moutou, C.; Pragt, J.; Rabou, P.; Saisse, M.; Schmid, H.M.; Turatto, M.; Udry, S.; Vakili, F.; Waters, R.; Wildi, F.

    2007-01-01

    Direct detection and spectral characterization of extra-solar planets is one of the most exciting but also one of the most challenging areas in modern astronomy. For its second generation instrumentation on the VLT, ESO has supported two phase A studies for a so-called Planet Finder dedicated instru

  5. The design of the MOONS-VLT spectrometer

    NARCIS (Netherlands)

    Oliva, E.; Diolaiti, E.; Garilli, B.; Gratton, R.; Lorenzetti, D.; Schipani, P.; Scuderi, S.; Vanzella, E.; Cirasuolo, M.; Afonso, J.; Bender, R.; Bonifacio, P.; Kaper, L.; Vanzi, L.; Baffa, C.; Bianco, A.; Bonoli, C.; Bortoletto, F.; Bruno, P.; Carbonaro, L.; Centrone, M.; Cresci, G.; De Caprio, V.; Del Vecchio, C.; Di Marcantonio, P.; Di Paola, A.; D'Alessio, F.; D'Alessandro, M.; D'Orsi, S.; Falcini, G.; Ferruzzi, D.; Fontana, A.; Foppiani, I.; Fumana, M.; Giani, E.; Leone, F.; Li Causi, G.; Lombini, M.; Maiolino, R.; Mannucci, F.; Marty, L.; Miglietta, L.; Munari, M.; Navarro, R.; Origlia, L.; Paioro, L.; Pedichini, F.; Pragt, J.; Randich, S.; Scodeggio, M.; Spano, P.; Speziali, R.; Stuik, R.; Tozzi, A.; Vitali, F.

    2012-01-01

    MOONS is a new conceptual design for a multi-object spectrograph for the ESO Very Large Telescope (VLT) which will provide the ESO astronomical community with a powerful, unique instrument able to serve a wide range of Galactic, Extragalactic and Cosmological studies. The instrument foresees 1000

  6. The science case of the CHEOPS planet finder for VLT

    NARCIS (Netherlands)

    Gratton, R.; Feldt, M.; Schmid, H.M.; Brandner, W.; Hippler, S.; Neuhauser, R.; Quirrenbach, A.; Desidera, S.; Turatto, M.; Stam, D.M.; Hasinger, G.; Turner, M.J.L.

    2004-01-01

    The CHEOPS Planet Finder is one of the proposed second generation instruments for the VLT. Its purpose is to image and characterize giant extrasolar planets in different phases of their evolution: young, warm planets as well as old, cold ones. Imaging the last ones is the most challenging task becau

  7. The design of the MOONS-VLT spectrometer

    NARCIS (Netherlands)

    Oliva, E.; Diolaiti, E.; Garilli, B.; Gratton, R.; Lorenzetti, D.; Schipani, P.; Scuderi, S.; Vanzella, E.; Cirasuolo, M.; Afonso, J.; Bender, R.; Bonifacio, P.; Kaper, L.; Vanzi, L.; Baffa, C.; Bianco, A.; Bonoli, C.; Bortoletto, F.; Bruno, P.; Carbonaro, L.; Centrone, M.; Cresci, G.; De Caprio, V.; Del Vecchio, C.; Di Marcantonio, P.; Di Paola, A.; D'Alessio, F.; D'Alessandro, M.; D'Orsi, S.; Falcini, G.; Ferruzzi, D.; Fontana, A.; Foppiani, I.; Fumana, M.; Giani, E.; Leone, F.; Li Causi, G.; Lombini, M.; Maiolino, R.; Mannucci, F.; Marty, L.; Miglietta, L.; Munari, M.; Navarro, R.; Origlia, L.; Paioro, L.; Pedichini, F.; Pragt, J.; Randich, S.; Scodeggio, M.; Spano, P.; Speziali, R.; Stuik, R.; Tozzi, A.; Vitali, F.

    2012-01-01

    MOONS is a new conceptual design for a multi-object spectrograph for the ESO Very Large Telescope (VLT) which will provide the ESO astronomical community with a powerful, unique instrument able to serve a wide range of Galactic, Extragalactic and Cosmological studies. The instrument foresees 1000 fi

  8. Hi-tech Flame

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Modern science plays a crucial role in lighting the Olympic flame on the world’s highest mountain when the world saw live telecasts of the Olympic flame burning onthe top of Mount Qomolangma(Mount Everest) at 9:17 on the morning of May 8, few realized the years of work and high level of technology that had

  9. Unsteady Flame Embedding

    KAUST Repository

    El-Asrag, Hossam A.

    2011-01-01

    Direct simulation of all the length and time scales relevant to practical combustion processes is computationally prohibitive. When combustion processes are driven by reaction and transport phenomena occurring at the unresolved scales of a numerical simulation, one must introduce a dynamic subgrid model that accounts for the multiscale nature of the problem using information available on a resolvable grid. Here, we discuss a model that captures unsteady flow-flame interactions- including extinction, re-ignition, and history effects-via embedded simulations at the subgrid level. The model efficiently accounts for subgrid flame structure and incorporates detailed chemistry and transport, allowing more accurate prediction of the stretch effect and the heat release. In this chapter we first review the work done in the past thirty years to develop the flame embedding concept. Next we present a formulation for the same concept that is compatible with Large Eddy Simulation in the flamelet regimes. The unsteady flame embedding approach (UFE) treats the flame as an ensemble of locally one-dimensional flames, similar to the flamelet approach. However, a set of elemental one-dimensional flames is used to describe the turbulent flame structure directly at the subgrid level. The calculations employ a one-dimensional unsteady flame model that incorporates unsteady strain rate, curvature, and mixture boundary conditions imposed by the resolved scales. The model is used for closure of the subgrid terms in the context of large eddy simulation. Direct numerical simulation (DNS) data from a flame-vortex interaction problem is used for comparison. © Springer Science+Business Media B.V. 2011.

  10. Hubble Tarantula Treasury Project V. The star cluster Hodge 301: the old face of 30 Doradus

    CERN Document Server

    Cignoni, M; van der Marel, R P; Lennon, D J; Tosi, M; Grebel, E K; Gallagher, J S; Aloisi, A; de Marchi, G; Gouliermis, D A; Larsen, S; Panagia, N; Smith, L J

    2016-01-01

    Based on color-magnitude diagrams (CMDs) from the Hubble Space Telescope Hubble Tarantula Treasury Project (HTTP) survey, we present the star formation history (SFH) of Hodge~301, the oldest star cluster in the Tarantula Nebula. The HTTP photometry extends faint enough to reach, for the first time, the cluster pre-main sequence (PMS) turn-on, where the PMS joins the main sequence. Using the location of this feature, along with synthetic CMDs generated with the latest PARSEC models, we find that Hodge~301 is older than previously thought, with an age between 26.5 and 31.5 Myr. From this age, we also estimate that between 38 and 61 supernovae Type-II exploded in the region. The same age is derived from the main sequence turn-off, whereas the age derived from the post-main sequence stars is younger and between 20 and 25 Myr. Other relevant parameters are a total stellar mass of $\\approx 8800\\,\\pm 800$M$_{\\odot}$ and average reddening E(B$-$V) $\\approx 0.22-0.24$ mag, with a differential reddening $\\delta$E(B$-$V...

  11. Hubble Tarantula Treasury Project V. The Star Cluster Hodge 301: The Old Face of 30 Doradus

    Science.gov (United States)

    Cignoni, M.; Sabbi, E.; van der Marel, R. P.; Lennon, D. J.; Tosi, M.; Grebel, E. K.; Gallagher, J. S., III; Aloisi, A.; de Marchi, G.; Gouliermis, D. A.; Larsen, S.; Panagia, N.; Smith, L. J.

    2016-12-01

    Based on color-magnitude diagrams (CMDs) from the Hubble Space Telescope Hubble Tarantula Treasury Project (HTTP) survey, we present the star formation history of Hodge 301, the oldest star cluster in the Tarantula Nebula. The HTTP photometry extends faint enough to reach, for the first time, the cluster pre-main sequence (PMS) turn-on, where the PMS joins the main sequence. Using the location of this feature, along with synthetic CMDs generated with the latest PARSEC models, we find that Hodge 301 is older than previously thought, with an age between 26.5 and 31.5 Myr. From this age, we also estimate that between 38 and 61 Type II supernovae exploded in the region. The same age is derived from the main sequence turn-off, whereas the age derived from the post-main sequence stars is younger and between 20 and 25 Myr. Other relevant parameters are a total stellar mass of ≈8800 ± 800 M ⊙ and average reddening E(B - V) ≈ 0.22-0.24 mag, with a differential reddening δE(B - V) ≈ 0.04 mag. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555.

  12. Successful "First Light" for VLT High-Resolution Spectrograph

    Science.gov (United States)

    1999-10-01

    Great Research Prospects with UVES at KUEYEN A major new astronomical instrument for the ESO Very Large Telescope at Paranal (Chile), the UVES high-resolution spectrograph, has just made its first observations of astronomical objects. The astronomers are delighted with the quality of the spectra obtained at this moment of "First Light". Although much fine-tuning still has to be done, this early success promises well for new and exciting science projects with this large European research facility. Astronomical instruments at VLT KUEYEN The second VLT 8.2-m Unit Telescope, KUEYEN ("The Moon" in the Mapuche language), is in the process of being tuned to perfection before it will be "handed" over to the astronomers on April 1, 2000. The testing of the new giant telescope has been successfully completed. The latest pointing tests were very positive and, from real performance measurements covering the entire operating range of the telescope, the overall accuracy on the sky was found to be 0.85 arcsec (the RMS-value). This is an excellent result for any telescope and implies that KUEYEN (as is already the case for ANTU) will be able to acquire its future target objects securely and efficiently, thus saving precious observing time. This work has paved the way for the installation of large astronomical instruments at its three focal positions, all prototype facilities that are capable of catching the light from even very faint and distant celestial objects. The three instruments at KUEYEN are referred to by their acronyms UVES , FORS2 and FLAMES. They are all dedicated to the investigation of the spectroscopic properties of faint stars and galaxies in the Universe. The UVES instrument The first to be installed is the Ultraviolet Visual Echelle Spectrograph (UVES) that was built by ESO, with the collaboration of the Trieste Observatory (Italy) for the control software. Complete tests of its optical and mechanical components, as well as of its CCD detectors and of the complex

  13. Image quality and high contrast improvements on VLT/NACO

    CERN Document Server

    Girard, Julien H V; Mawet, Dimitri; Kasper, Markus; Zins, Gérard; Neichel, Benoît; Kolb, Johann; Christiaens, Valentin; Tourneboeuf, Martin; 10.1117/12.925660

    2012-01-01

    NACO is the famous and versatile diffraction limited NIR imager and spectrograph with which ESO celebrated 10 years of Adaptive Optics at the VLT. Since two years a substantial effort has been put in to understanding and fixing issues that directly affect the image quality and the high contrast performances of the instrument. Experiments to compensate the non-common-path aberrations and recover the highest possible Strehl ratios have been carried out successfully and a plan is hereafter described to perform such measurements regularly. The drift associated to pupil tracking since 2007 was fixed in October 2011. NACO is therefore even better suited for high contrast imaging and can be used with coronagraphic masks in the image plane. Some contrast measurements are shown and discussed. The work accomplished on NACO will serve as reference for the next generation instruments on the VLT, especially those working at the diffraction limit and making use of angular differential imaging (i.e. SPHERE, VISIR, possibly ...

  14. New BVRI photometry results on KBOs from the ESO VLT

    CERN Document Server

    Santos-Sanz, P; Barrera, L; Boehnhardt, H

    2008-01-01

    Photometric surveys of transNeptunian objects (TNOs) and Centaurs have suggested possible correlations between some orbital parameters and surface colors of classical objects, scattered disk objects (SDOs), and Centaurs. However, larger sample sizes are needed in order to corroborate or rule out the possible correlations and find some possible new ones. We use VLT-FORS images through BVRI filters of 32 Kuiper Belt Objects (KBOs) and obtain their colors after proper reduction and calibration. We study the possible correlations merging these new measurements with the VLT published results from the ESO large program and with the latest published results of the Meudon Multicolor Survey via non-parametric statistical tests. We obtain a large dataset of 116 objects (classical, SDOs and Centaurs) and, in addition to confirming most of the correlations and conclusions reached in the literature, some possible new correlations are found. The most interesting ones are some correlations of color vs. orbital parameters fo...

  15. Igniting the Paralympic Flame

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Deaf-mute Jiang Xintian lights a small cauldron in the hands of wheelchairbound fencer Jin Jing at the Paralympic Flame Lighting Ceremony in Beijing’s symbolic Temple of Heaven on August 28. For nine days until September 6, when the 13th Paralympics opens in Beijing, a total of 850 torchbearers would relay the Paralympic flame along two routes through 11 Chinese provinces,

  16. The AVES adaptive optics spectrograph for the VLT: status report

    Science.gov (United States)

    Pallavicini, Roberto; Delabre, Bernard; Pasquini, Luca; Zerbi, Filippo M.; Bonanno, Giovanni; Comari, Maurizio; Conconi, Paolo; Mazzoleni, Ruben; Santin, Paolo; Damiani, Francesco; Di Marcantonio, Paolo; Franchini, Mariagrazia; Spano, Paolo; Bonifacio, P.; Catalano, Santo; Molaro, Paolo P.; Randich, S.; Rodono, Marcello

    2003-03-01

    We report on the status of AVES, the Adaptive-optics Visual Echelle Spectrograph proposed for the secondary port of the Nasmyth Adaptive Optics System (NAOS) recently installed at the VLT. AVES is an intermediate resolution (R ≍ 16,000) high-efficiency fixed- format echelle spectrograph which operates in the spectral band 500 - 1,000 nm. In addition to a high intrinsic efficiency, comparable to that of ESI at Keck II, it takes advantage of the adaptive optics correction provided by NAOS to reduce the sky and detector contribution in background-limited observations of weak sources, thus allowing a further magnitude gain with respect to comparable non-adaptive optics spectrographs. Simulations show that the instrument will be capable of reaching a magnitude V = 22.5 at S/N > 10 in two hours, two magnitudes weaker than GIRAFFE at the same resolution and 3 magnitudes weaker than the higher resolution UVES spectrograph. Imaging and coronographic functions have also been implemented in the design. We present the results of the final design study and we dicuss the technical and operational issues related to its implementation at the VLT as a visitor instrument. We also discuss the possibility of using a scaled-up non-adaptive optics version of the same design as an element of a double- or triple-arm intermediate-resolution spectrograph for the VLT. Such an option looks attractive in the context of a high-efficiency large-bandwidth (320 - 1,500 nm) spectrograph ("fast-shooter") being considered by ESO as a 2nd-generation VLT instrument.

  17. Designing a common real-time controller for VLT applications

    Science.gov (United States)

    Bauvir, Bertrand; Wallander, Anders; Duhoux, Philippe; Huxley, Alexis; Karban, Robert

    2004-09-01

    The increasing number of digital control applications in the context of the VLT, and particularly the VLT Interferometer, brought the need to find a common solution to address the problems of performance and maintainability. Tools for Advanced Control (TAC) aims at helping both control and software engineers in the design and prototyping of real-time control applications by providing them with a set of standard functions and an easy way to combine them to create complex control algorithms. In this paper we describe the software architecture and design of TAC, the VLT standard for digital control applications. Algorithms are described at schematic level and take the form of a set of interconnected function blocks. Periodical execution of the algorithm as well as features like runtime modification of parameters and probing of internal data are also managed by TAC, allowing the application designers to avoid spending time writing low value software code and therefore focus on application-specific concerns. We also summarize the results achieved on the first actual applications using TAC, to manage real-time control or digital signal processing algorithms, currently deployed and being commissioned at Paranal Observatory.

  18. Hubble Tarantula Treasury Project: Unraveling Tarantula's Web. II. Optical and Near Infrared Star Formation History of the Starburst Cluster NGC 2070 in 30 Doradus

    CERN Document Server

    Cignoni, M; van der Marel, R P; Tosi, M; Zaritsky, D; Anderson, J; Lennon, D J; Aloisi, A; de Marchi, G; Gouliermis, D A; Grebel, E K; Smith, L J; Zeidler, P

    2015-01-01

    We present a study of the recent star formation of 30 Doradus in the Large Magellanic Cloud (LMC) using the panchromatic imaging survey Hubble Tarantula Treasury Project (HTTP). In this paper we focus on the stars within 20 pc of the center of the massive ionizing cluster of 30 Doradus, NGC 2070. We recovered the star formation history by comparing deep optical and NIR color-magnitude diagrams (CMDs) with state-of-the-art synthetic CMDs generated with the latest PARSEC models, which include all stellar phases from pre-main sequence to post- main sequence. For the first time in this region we are able to measure the star formation using intermediate and low mass stars simultaneously. Our results suggest that NGC2070 experienced a prolonged activity. In particular, we find that the star formation in the region: i) exceeded the average LMC rate ~ 20 Myr ago; ii) accelerated dramatically ~ 7 Myr ago; and iii) reached a peak value 1-3 Myr ago. We did not find significant deviations from a Kroupa initial mass funct...

  19. Explosive Model Tarantula 4d/JWL++ Calibration of LX-17

    Energy Technology Data Exchange (ETDEWEB)

    Souers, P C; Vitello, P A

    2008-09-30

    Tarantula is an explosive kinetic package intended to do detonation, shock initiation, failure, corner-turning with dead zones, gap tests and air gaps in reactive flow hydrocode models. The first, 2007-2008 version with monotonic Q is here run inside JWL++ with square zoning from 40 to 200 zones/cm on ambient LX-17. The model splits the rate behavior in every zone into sections set by the hydrocode pressure, P + Q. As the pressure rises, we pass through the no-reaction, initiation, ramp-up/failure and detonation sections sequentially. We find that the initiation and pure detonation rate constants are largely insensitive to zoning but that the ramp-up/failure rate constant is extremely sensitive. At no time does the model pass every test, but the pressure-based approach generally works. The best values for the ramp/failure region are listed here in Mb units.

  20. Workshop “Science with the VLT in the ELT Era”

    CERN Document Server

    Astrophysics and Space Science Proceedings

    2008-01-01

    The Workshop ‘Science with the VLT in the ELT era’ was organised by ESO as a forum for the astronomical community to debate its expected future use of ESO’s Very Large Telescope ( and its VLTI interferometric mode) when other facilities such as ALMA, JWST and, hopefully, at least one extremely large 30-40m class telescope will be operating. VLT/I science highlights were presented, future science priorities argued, synergies between the VLT and the future facilities confirmed and specific new VLT/I instruments proposed.

  1. A case of zootherapy with the tarantula Brachypelma vagans Ausserer, 1875 in traditional medicine of the Chol Mayan ethnic group in Mexico

    Directory of Open Access Journals (Sweden)

    Rojo Roberto

    2011-03-01

    Full Text Available Abstract Background In practically every human culture, the use of arthropods as medicinal resources has been reported. In Mexico, the Mayan people mainly use plants but occasionally also animals and minerals in their medicine. This article is the first to report the traditional use of the tarantula Brachypelma vagans by medicine men in the Chol community, an ancient indigenous group that inhabits the southeastern part of Mexico. We also describe the utility of such arachnids in traditional medicine. Methods This study was carried out in different Chol communities in the states of Chiapas and Campeche (southeastern Mexico from 2003 until 2007. We interviewed the local medicine men, patients and non-Chol people in each village visited to collect information about the rituals involved and the effectiveness of this traditional medicine and also their opinion of this traditional medicine. Results In all independent villages, the people who present an illness called 'aire de tarantula' or tarantula wind with symptoms including chest pain, coughing and asthma, were treated by the medicine man (called 'hierbatero' with a tarantula-based beverage. From village to village, the beverage has a similar base composition but some variations occur in additional ingredients depending on the individual medicine man. Like in all traditional Mayan medicine, the ritual of the ceremony consists of drinking the tarantula-based beverage and this is principally accompanied by chants and burning of incense. Conclusions The recipe of the tarantula-based beverage and the procedure of this ritual ceremony were fairly constant in all the villages visited. Our work shows that despite the tarantula's bad image in several cultures, in others positive use is made of these spiders, as in modern medicine.

  2. Evolution of supercontraction in spider silk: structure-function relationship from tarantulas to orb-weavers.

    Science.gov (United States)

    Boutry, Cecilia; Blackledge, Todd Alan

    2010-10-15

    Spider silk is a promising biomaterial with impressive performance. However, some spider silks also 'supercontract' when exposed to water, shrinking by up to ∼50% in length. Supercontraction may provide a critical mechanism to tailor silk properties, both for future synthetic silk production and by the spiders themselves. Several hypotheses are proposed for the mechanism and function of supercontraction, but they remain largely untested. In particular, supercontraction may result from a rearrangement of the GPGXX motif within the silk proteins, where G represents glycine, P proline and X is one of a small subset of amino acids. Supercontraction may prevent sagging in wet orb-webs or allow spiders to tailor silk properties for different ecological functions. Because both the molecular structures of silk proteins and how dragline is used in webs differ among species, we can test these hypotheses by comparing supercontraction of silk across diverse spider taxa. In this study we measured supercontraction in 28 spider taxa, ranging from tarantulas to orb-weaving spiders. We found that silk from all species supercontracted, except that of most tarantulas. This suggests that supercontraction evolved at least with the origin of the Araneomorphae, over 200 million years ago. We found differences in the pattern of evolution for two components of supercontraction. Stress generated during supercontraction of a restrained fiber is not associated with changes in silk structure and web architecture. By contrast, the shrink of unrestrained supercontracting fibers is higher for Orbiculariae spiders, whose silk contains high ratios of GPGXX motifs. These results support the hypothesis that supercontraction is caused by a rearrangement of GPGXX motifs in silk, and that it functions to tailor silk material properties.

  3. Flaming on YouTube

    NARCIS (Netherlands)

    Moor, Peter J.; Heuvelman, A.; Verleur, R.

    2010-01-01

    In this explorative study, flaming on YouTube was studied using surveys of YouTube users. Flaming is defined as displaying hostility by insulting, swearing or using otherwise offensive language. Three general conclusions were drawn. First, although many users said that they themselves do not flame,

  4. Flaming on YouTube

    NARCIS (Netherlands)

    Moor, Peter J.; Heuvelman, Ard; Verleur, Ria

    2010-01-01

    In this explorative study, flaming on YouTube was studied using surveys of YouTube users. Flaming is defined as displaying hostility by insulting, swearing or using otherwise offensive language. Three general conclusions were drawn. First, although many users said that they themselves do not flame,

  5. Effects of sevoflurane anesthesia on righting reflex and hemolymph gas analysis variables for Chilean rose tarantulas (Grammostola rosea).

    Science.gov (United States)

    Zachariah, Trevor T; Mitchell, Mark A; Watson, Megan K; Clark-Price, Stuart C; McMichael, Maureen A

    2014-06-01

    To determine the safety, efficacy, and effects on hemolymph gas analysis variables of sevoflurane anesthesia in Chilean rose tarantulas (Grammostola rosea). 12 subadult Chilean rose tarantulas of unknown sex. Spiders were anesthetized in a custom chamber with sevoflurane (5% in oxygen [1.0 L/min]), then allowed to recover in 100% oxygen. Righting reflex was evaluated every 3 minutes during anesthesia to determine time to anesthetic induction and recovery. Hemolymph samples were collected from an intracardiac location prior to and after induction of anesthesia and evaluated to determine various gas analysis variables. Mean ± SD induction and recovery times were 16 ± 5.91 minutes and 29 ± 21.34 minutes, respectively. Significant differences were detected for Po2, base excess, and glucose and ionized magnesium concentrations between hemolymph samples obtained before anesthesia and those obtained after induction of anesthesia. CONCLUSIONS AND CLINICAL RELEVANCE-Results of this study suggested that the use of sevoflurane as an anesthetic agent for Chilean rose tarantulas was safe and effective. Various hemolymph sample gas analysis values changed during anesthesia.

  6. ESPRESSO: the ultimate rocky exoplanets hunter for the VLT

    Science.gov (United States)

    Mégevand, Denis; Zerbi, Filippo M.; Cabral, Alexandre; Di Marcantonio, Paolo; Amate, Manuel; Pepe, Francesco; Cristiani, Stefano; Rebolo, Rafael; Santos, Nuno C.; Dekker, Hans; Abreu, Manuel; Affolter, Michael; Avila, Gerardo; Baldini, Veronica; Bristow, Paul; Broeg, Christopher; Carvas, Pedro; Cirami, Roberto; Coelho, João.; Comari, Maurizio; Conconi, Paolo; Coretti, Igor; Cupani, Guido; D'Odorico, Valentina; De Caprio, Vincenzo; Delabre, Bernard; Figueira, Pedro; Fleury, Michel; Fragoso, Ana; Genolet, Ludovic; Gomes, Ricardo; Gonzalez Hernandez, Jonay; Hughes, Ian; Iwert, Olaf; Kerber, Florian; Landoni, Marco; Lima, Jorge; Lizon, Jean-Louis; Lovis, Christophe; Maire, Charles; Mannetta, Marco; Martins, Carlos; Moitinho, André; Molaro, Paolo; Monteiro, Manuel; Rasilla, José Luis; Riva, Marco; Santana Tschudi, Samuel; Santin, Paolo; Sosnowska, Danuta; Sousa, Sergio; Spanò, Paolo; Tenegi, Fabio; Toso, Giorgio; Vanzella, Eros; Viel, Matteo; Zapatero Osorio, Maria Rosa

    2012-09-01

    ESPRESSO, the VLT rocky exoplanets hunter, will combine the efficiency of modern echelle spectrograph with extreme radial-velocity precision. It will be installed at Paranal on ESO's VLT in order to achieve a gain of two magnitudes with respect to its predecessor HARPS, and the instrumental radial-velocity precision will be improved to reach 10 cm/s level. We have constituted a Consortium of astronomical research institutes to fund, design and build ESPRESSO on behalf of and in collaboration with ESO, the European Southern Observatory. The project has passed the preliminary design review in November 2011. The spectrograph will be installed at the so-called "Combined Coudé Laboratory" of the VLT, it will be linked to the four 8.2 meters Unit Telescopes (UT) through four optical "Coudé trains" and will be operated either with a single telescope or with up to four UTs. In exchange of the major financial and human effort the building Consortium will be awarded with guaranteed observing time (GTO), which will be invested in a common scientific program. Thanks to its characteristics and the ability of combining incoherently the light of 4 large telescopes, ESPRESSO will offer new possibilities in many fields of astronomy. Our main scientific objectives are, however, the search and characterization of rocky exoplanets in the habitable zone of quiet, near-by G to M-dwarfs, and the analysis of the variability of fundamental physical constants. In this paper, we present the ambitious scientific objectives, the capabilities of ESPRESSO, the technical solutions for the system and its subsystems, enlightening the main differences between ESPRESSO and its predecessors. The project aspects of this facility are also described, from the consortium and partnership structure to the planning phases and milestones.

  7. VLT telescope control software: status, development, and lessons learned

    Science.gov (United States)

    Wirenstrand, Krister

    2003-02-01

    The four 8m VLT telescopes on Paranal are now in full science operation, and they all deliver good results with very small technical downtimes. Of course, many factors are contributing to these results, and also the telescope control software has its share. It has demonstrated to be robust and reliable and also flexible and expandable. In the four years since First Light of the first VLT telescope, this software has been continuously maintained and developed, for improvements on the 8m telescopes but also for use on other telescopes. In addition to the 8m ones, another three telescopes, using applicable parts of the same software, are in operation on Paranal: the 350- mm seeing monitor and two 400-mm siderostats. And the process continues: in the beginning of 2003 the first of three 1.8m Auxiliary Telescopes for the VLT Interferometer will be installed; the control software to 80% being the same as for the 8m telescopes, but with additional devices and control functionality. Another three ESO telescopes on La Silla are also using the same software, as well as two wide field telescopes for Paranal that are now in the design and manufacturing phase. In this development process, and in particular after first installation, we have learned lessons in many areas of software project work. System design and engineering, standardization, tools, testing: these are example areas where there is always room for improvement. Another lesson learned is the importance of the concept of Commissioning, i.e. the work to take the telescope from "integrated" to "working"! What the future of telescope control software will be, that we don't know, but we are working on it! And we try to keep an evolutionary approach, taking advantage of the lessons learned.

  8. ESO Council Decides to Continue VLT Project at Paranal

    Science.gov (United States)

    1994-08-01

    The Council [1] of the European Southern Observatory has met in extraordinary session at the ESO Headquarters in Garching near Munich on August 8 and 9, 1994. The main agenda items were concerned with the recent developments around ESO's relations with the host state, the Republic of Chile, as well as the status of the organisation's main project, the 16-metre equivalent Very Large Telescope (VLT) which will become the world's largest optical telescope. Council had decided to hold this special meeting [2] because of various uncertainties that have arisen in connection with the implementation of the VLT Project at Cerro Paranal, approx. 130 kilometres south of Antofagasta, capital of the II Region in Chile. Following continued consultations at different levels within the ESO member states and after careful consideration of all aspects of the current situation - including various supportive actions by the Chilean Government as well as the incessive attacks against this international organisation from certain sides reported in the media in that country - Council took the important decision to continue the construction of the VLT Observatory at Paranal, while at the same time requesting the ESO Management to pursue the ongoing studies of alternative solutions. THE COUNCIL DECISIONS In particular, the ESO Council took note of recent positive developments which have occurred since the May 1994 round of discussions with the Chilean authorities in Santiago. The confirmation of ESO's immunities as an International Organization in Chile, contained in a number of important statements and documents, is considered a significant step by the Chilean Government to insure to ESO the unhindered erection and later operation of the VLT on Paranal. Under these circumstances and in order to maintain progress on the VLT project, the ESO Council authorized the ESO Management to continue the on-site work at Paranal. Council also took note of the desire expressed by the Chilean Government

  9. VLT/NACO observations of Neptune's ring arcs

    Science.gov (United States)

    Renner, S.; Sicardy, B.; Souami, D.; Dumas, C.

    2011-10-01

    We present NACO adaptative optics observations of Neptune's ring arcs at 2.2 μm (K band), taken with the VLT-Yepun telescope in August 2007. We give improved mean motion values for the arcs and Galatea, thus confirming the mismatch between the arcs' position and the location of the 42:43 corotation inclination resonance. We compare the photometry of the arcs with previous observations. We finally use the data to constrain the masses and positions of the coorbital satellites which could confine the arcs, while allowing a slow evolution of the system.

  10. VLT instrumentation control: the collaboration of OATs with ESO

    Science.gov (United States)

    Santin, P.

    The collaboration of the Astrophysics Technology Group (ATG) of the Astronomical Observatory of Trieste with ESO will be presented. It may be considered as an example of a good practice in the collaboration of a peripheral Institute with ESO. Started in 1985, it spans almost all the time since Italy joined ESO in 1982. The Trieste Astrophysics Technology Group (ATG) participated in many technological enterprise of ESO, from Remote Observing to VLT instrumentation and to ALMA ACS, and is now looking for the challenging E-ELT.

  11. VLT spectroscopy of massive stars in NGC55

    Directory of Open Access Journals (Sweden)

    N. Castro

    2007-01-01

    Full Text Available We present the first spectroscopy study of massive stars in NGC55. The data, taken with VLT-FORS2 allow us to provide spectral classification for 200 objects located through- out the galaxy. From this sample, suitable B-type supergiants are chosen for subsequent higher resolution spectroscopic observations that will enable a quantitative study. The stellar abundances will be a key point in the study of galaxy chemical evolution. We also discuss how GTC-OSIRIS can be a valuable tool for similar studies.

  12. Flame Stretch Analysis in Diffusion Flames with Inert Gas

    Institute of Scientific and Technical Information of China (English)

    Ay Su; Ying-Chieh Liu

    2001-01-01

    Experimental investigations of impinging flame with fuel mixed with non-reaction gas were conducted.According to the observations of combustion test and temperature measurement, the non-reaction gas might dilute the local concentration of fuel in the diffusion process. The shape of the flame was symmetrical due to the flame stretch force. Results show that the conical flame might be de-structured by the addition of inert gas in pure methane fuel. The impinging flame became shorter and bluer as nitrogen was added to the fuel. The conditions of N2/CH4 equal to 1/2 and 1/1 show a wider plane in the YZ plane. The effect of inert gas overcomes the flame stretch and destroys the symmetrical column flame as well as the cold flow. Nitrogen addition also enhances the diffusion rate and combustion efficiency.

  13. Propagation Limits of High Pressure Cool Flames

    Science.gov (United States)

    Ju, Yiguang

    2016-11-01

    The flame speeds and propagation limits of premixed cool flames at elevated pressures with radiative heat loss are numerically modelled using dimethyl ether mixtures. The primary focus is paid on the effects of pressure, mixture dilution, flame size, and heat loss on cool flame propagation. The results showed that cool flames exist on both fuel lean and fuel rich sides and thus dramatically extend the lean and rich flammability limits. There exist three different flame regimes, hot flame, cool flame, and double flame. A new flame flammability diagram including both cool flames and hot flames is obtained at elevated pressure. The results show that pressure significantly changes cool flame propagation. It is found that the increases of pressure affects the propagation speeds of lean and rich cool flames differently due to the negative temperature coefficient effect. On the lean side, the increase of pressure accelerates the cool flame chemistry and shifts the transition limit of cool flame to hot flame to lower equivalence ratio. At lower pressure, there is an extinction transition from hot flame to cool flame. However, there exists a critical pressure above which the cool flame to hot flame transition limit merges with the lean flammability limit of the hot flame, resulting in a direct transition from hot flame to cool flame. On the other hand, the increase of dilution reduces the heat release of hot flame and promotes cool flame formation. Moreover, it is shown that a smaller flame size and a higher heat loss also extend the cool flame transition limit and promote cool flame formation.

  14. A valiant little terminal: A VLT user's manual

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, A.

    1990-12-01

    This report is a manual for the valiant little terminal. Information covered in this report is as follow: an introduction to VLT; installation; starting up; text screen menus; graphics screen menus; introduction to VLT's scripting facility; quick reference section; and troubleshooting.

  15. MOONS: the Multi-Object Optical and Near-infrared Spectrograph for the VLT

    NARCIS (Netherlands)

    M. Cirasuolo; . et al.; L. Kaper; B. Lemasle

    2014-01-01

    MOONS is a new Multi-Object Optical and Near-infrared Spectrograph selected by ESO as a third generation instrument for the Very Large Telescope (VLT). The grasp of the large collecting area offered by the VLT (8.2m diameter), combined with the large multiplex and wavelength coverage (optical to nea

  16. "Magic Eraser" Flame Tests

    Science.gov (United States)

    Landis, Arthur M.; Davies, Malonne I.; Landis, Linda

    2009-01-01

    Cleaning erasers are used to support methanol-fueled flame tests. This safe demonstration technique requires only small quantities of materials, provides clean colors for up to 45 seconds, and can be used in the classroom or the auditorium. (Contains 1 note.)

  17. AVES: an adaptive optics visual echelle spectrograph for the VLT

    Science.gov (United States)

    Pasquini, Luca; Delabre, Bernard; Avila, Gerardo; Bonaccini, Domenico

    1998-07-01

    We present the preliminary study of a low cost, high performance spectrograph for the VLT, for observations in the V, R and I bands. This spectrograph is meant for intermediate (R equals 16,000) resolution spectroscopy of faint (sky and/or detector limited) sources, with particular emphasis on the study of solar-type (F-G) stars belonging to the nearest galaxies and to distant (or highly reddened) galactic clusters. The spectrograph is designed to use the adaptive optics (AO) systems at the VLT Telescope. Even if these AO systems will not provide diffraction limited images in the V, R and I bands, the photon concentration will still be above approximately 60% of the flux in an 0.3 arcsecond aperture for typical Paranal conditions. This makes the construction of a compact, cheap and efficient echelle spectrograph possible. AVES will outperform comparable non adaptive optic instruments by more than one magnitude for sky- and/or detector-limited observations, and it will be very suitable for observations in crowded fields.

  18. Flame Retardant Epoxy Resins

    Science.gov (United States)

    Thompson, C. M.; Smith, J. G., Jr.; Connell, J. W.; Hergenrother, P. M.; Lyon, R. E.

    2004-01-01

    As part of a program to develop fire resistant exterior composite structures for future subsonic commercial aircraft, flame retardant epoxy resins are under investigation. Epoxies and their curing agents (aromatic diamines) containing phosphorus were synthesized and used to prepare epoxy formulations. Phosphorus was incorporated within the backbone of the epoxy resin and not used as an additive. The resulting cured epoxies were characterized by thermogravimetric analysis, propane torch test, elemental analysis and microscale combustion calorimetry. Several formulations showed excellent flame retardation with phosphorous contents as low as 1.5% by weight. The fracture toughness of plaques of several cured formulations was determined on single-edge notched bend specimens. The chemistry and properties of these new epoxy formulations are discussed.

  19. Antimony: a flame fighter

    Science.gov (United States)

    Wintzer, Niki E.; Guberman, David E.

    2015-01-01

    Antimony is a brittle, silvery-white semimetal that conducts heat poorly. The chemical compound antimony trioxide (Sb2O3) is widely used in plastics, rubbers, paints, and textiles, including industrial safety suits and some children’s clothing, to make them resistant to the spread of flames. Also, sodium antimonate (NaSbO3) is used during manufacturing of high-quality glass, which is found in cellular phones.

  20. Chemical abundances in the protoplanetary disk LV2 (Orion) - II: High dispersion VLT observations and microjet properties

    CERN Document Server

    Tsamis, Y G

    2011-01-01

    Integral field spectroscopy of the LV2 proplyd is presented taken with the VLT/FLAMES Argus array at an angular resolution of 0.31x0.31 arcsec^2 and velocity resolutions down to 2 km/s per pixel. Following subtraction of the local M42 emission, the spectrum of LV2 is isolated from the surrounding nebula. We measured the heliocentric velocities and widths of a number of lines detected in the intrinsic spectrum of the proplyd, as well as in the adjacent Orion nebula within a 6.6 x 4.2 arcsec^2 FoV. It is found that far-UV to optical collisional lines with critical densities, Ncrit, ranging from 10^3 to 10^9 /cm^3 suffer collisional de-excitation near the rest velocity of the proplyd correlating tightly with their critical densities. Lines of low Ncrit are suppressed the most. The bipolar jet arising from LV2 is spectrally and spatially well-detected in several emission lines. We compute the [O III] electron temperature profile across LV2 in velocity space and measure steep temperature variations associated with...

  1. Dynamics of unconfined spherical flames

    CERN Document Server

    Leblanc, Louis; Dennis, Kadeem; Zhe,; Liang,; Radulescu, Matei I

    2012-01-01

    Using the soap bubble technique, we visualize the dynamics of unconfined hydrogen-air flames using high speed schlieren video. We show that for sufficiently weak mixtures, i.e., low flame speeds, buoyancy effects become important. Flame balls of a critical dimension begin to rise. The experiments are found in very good agreement with the scaling laws proposed by Zingale and Dursi. We report the results in a fluid dynamics video.

  2. The massive monsters living deep in the Tarantula nebula: How massive are they really?

    Science.gov (United States)

    de Mink, Selma

    2013-10-01

    The recent suggestion that stars with masses in excess of about 300 solar masses exist in the dense star cluster R136 at heart of the Tarantula Nebula received wide interest. It reopened the debate about the upper stellar-mass limit of the initial mass function {IMF} and it raised the question whether pair-instability supernovae - originally thought exclusively originate from first generation of pop III stars - can occur in the vicinity of Milky Way.A major challenge hampering mass estimates of the most massive stars is crowding and unresolved companions. High-resolution imaging from the ground and with HST reaching resolutions of about 0.1 arcsec resolved the brightest source in R136 into three separate components. Unfortunately, the extreme crowding and faintness of the targets prohibits ground-based facilities to reach further towards mili-arcsecond resolution.We propose to exploit the new full two-dimensional calibration program of Fine Guidance Sensor {Nelan, Prop ID 13175} to probe the most luminous stars in R136 for previously unseen companions down to a resolution of 12 mili-arsecond, exploring the separation of about 500-5000 AU. Furthermore, we will characterize the claimed source R136-a1B and if needed revise downward the mass estimates of the most massive stars known date.

  3. Clinical presentation and outcome of Sri-Lankan Ornamental Tarantula Poecilotheria fasciata spider bite: a case report

    Directory of Open Access Journals (Sweden)

    NP Dinamithra

    2013-10-01

    Full Text Available We report on a 19-year-old boy with visible muscle spasms admitted to the hospitals 24 hours after spider bite. He was treated effectively with intravenous calcium gluconate followed by oral calcium supplements and made a full recovery 48 hours after the incident. Although no specific treatment exists in Srilanka, it has been suggested that calcium supplements may be beneficial to relieve the muscle spasms. Our patient made a full recovery with calcium supplements suggesting the treatment with calcium is beneficial in relieving the pain and muscle spasms caused by Sri-Lankan Ornamental Tarantula Poecilotheria fasciata.

  4. Calibration strategy of the pyramid wavefront sensor module of ERIS with the VLT deformable secondary mirror

    Science.gov (United States)

    Riccardi, A.; Briguglio, R.; Pinna, E.; Agapito, G.; Quiros-Pacheco, F.; Esposito, S.

    2012-07-01

    ERIS is a new Adaptive Optics Instrument for the Adaptive Optics Facility of the VLT that foresees, in its design phase, a Pyramid Wavefront Sensor Module (PWM) to be used with the VLT Deformable Secondary Mirror (VLT-DSM) as corrector. As opposite to the concave secondary mirrors currently in use (e.g. at LBT), VLT-DSM is convex and calibration of the interaction matrix (IM) between the PWM and the DSM is not foreseen on-telescope during day-time. In this paper different options of calibration are evaluated and compared with particular attention on the synthetic evaluation and on-sky calibration of the IM. A trade-off of the calibration options, the optimization techniques and the related validation with numerical simulations are also provided.

  5. Solid Propellant Flame Spectroscopy

    Science.gov (United States)

    1988-08-01

    400 jm to reach the maximum flame temperature, a distance that can be reduced by replacing the HTPB binder with a polyester or CMDB binder. The...the dark zone for propellants similar to HIX2 is 2-2.5 mm at 1.8 MPa (18 atm, 265 psia) (Ref. 22,187). In contrast, the dark zone for HMX CMDB ...propellants eliminates the dark zone is not surprising, since TMETN is a nitrate ester as was the double-base matrix of Kubota’s HMX CMDB propellant. A

  6. Dynamics and structure of stretched flames

    Energy Technology Data Exchange (ETDEWEB)

    Law, C.K. [Princeton Univ., NJ (United States)

    1993-12-01

    This program aims to gain fundamental understanding on the structure, geometry, and dynamics of laminar premixed flames, and relate these understanding to the practical issues of flame extinction and stabilization. The underlying fundamental interest here is the recent recognition that the response of premixed flames can be profoundly affected by flame stretch, as manifested by flow nonuniformity, flame curvature, and flame/flow unsteadiness. As such, many of the existing understanding on the behavior of premixed flames need to be qualitatively revised. The research program consists of three major thrusts: (1) detailed experimental and computational mapping of the structure of aerodynamically-strained planar flames, with emphasis on the effects of heat loss, nonequidiffusion, and finite residence time on the flame thickness, extent of incomplete reaction, and the state of extinction. (2) Analytical study of the geometry and dynamics of stretch-affected wrinkled flame sheets in simple configurations, as exemplified by the Bunsen flame and the spatially-periodic flame, with emphasis on the effects of nonlinear stretch, the phenomena of flame cusping, smoothing, and tip opening, and their implications on the structure and burning rate of turbulent flames. (3) Stabilization and blowoff of two-dimensional inverted premixed and stabilization and determining the criteria governing flame blowoff. The research is synergistically conducted through the use of laser-based diagnostics, computational simulation of the flame structure with detailed chemistry and transport, and mathematical analysis of the flame dynamics.

  7. Two VLT 8.2-m Unit Telescopes in Action

    Science.gov (United States)

    1999-04-01

    Visitors at ANTU - Astronomical Images from KUEYEN The VLT Control Room at the Paranal Observatory is becoming a busy place indeed. From here, two specialist teams of ESO astronomers and engineers now operate two VLT 8.2-m Unit Telescopes in parallel, ANTU and KUEYEN (formerly UT1 and UT2, for more information about the naming and the pronunciation, see ESO Press Release 06/99 ). Regular science observations have just started with the first of these giant telescopes, while impressive astronomical images are being obtained with the second. The work is hard, but the mood in the control room is good. Insiders claim that there have even been occasions on which the groups have had a friendly "competition" about which telescope makes the "best" images! The ANTU-team has worked with the FORS multi-mode instrument , their colleagues at KUEYEN use the VLT Test Camera for the ongoing tests of this new telescope. While the first is a highly developed astronomical instrument with a large-field CCD imager (6.8 x 6.8 arcmin 2 in the normal mode; 3.4 x 3.4 arcmin 2 in the high-resolution mode), the other is a less complex CCD camera with a smaller field (1.5 x 1.5 arcmin 2 ), suited to verify the optical performance of the telescope. As these images demonstrate, the performance of the second VLT Unit Telescope is steadily improving and it may not be too long before its optical quality will approach that of the first. First KUEYEN photos of stars and galaxies We present here some of the first astronomical images, taken with the second telescope, KUEYEN, in late March and early April 1999. They reflect the current status of the optical, electronic and mechanical systems, still in the process of being tuned. As expected, the experience gained from ANTU last year has turned out to be invaluable and has allowed good progress during this extremely delicate process. ESO PR Photo 19a/99 ESO PR Photo 19a/99 [Preview - JPEG: 400 x 433 pix - 160k] [Normal - JPEG: 800 x 866 pix - 457k] [High

  8. Isolation of an orally active insecticidal toxin from the venom of an Australian tarantula.

    Directory of Open Access Journals (Sweden)

    Margaret C Hardy

    Full Text Available Many insect pests have developed resistance to existing chemical insecticides and consequently there is much interest in the development of new insecticidal compounds with novel modes of action. Although spiders have deployed insecticidal toxins in their venoms for over 250 million years, there is no evolutionary selection pressure on these toxins to possess oral activity since they are injected into prey and predators via a hypodermic needle-like fang. Thus, it has been assumed that spider-venom peptides are not orally active and are therefore unlikely to be useful insecticides. Contrary to this dogma, we show that it is possible to isolate spider-venom peptides with high levels of oral insecticidal activity by directly screening for per os toxicity. Using this approach, we isolated a 34-residue orally active insecticidal peptide (OAIP-1 from venom of the Australian tarantula Selenotypus plumipes. The oral LD50 for OAIP-1 in the agronomically important cotton bollworm Helicoverpa armigera was 104.2±0.6 pmol/g, which is the highest per os activity reported to date for an insecticidal venom peptide. OAIP-1 is equipotent with synthetic pyrethroids and it acts synergistically with neonicotinoid insecticides. The three-dimensional structure of OAIP-1 determined using NMR spectroscopy revealed that the three disulfide bonds form an inhibitor cystine knot motif; this structural motif provides the peptide with a high level of biological stability that probably contributes to its oral activity. OAIP-1 is likely to be synergized by the gut-lytic activity of the Bacillus thuringiensis Cry toxin (Bt expressed in insect-resistant transgenic crops, and consequently it might be a good candidate for trait stacking with Bt.

  9. Species delimitation and phylogeography of Aphonopelma hentzi (Araneae, Mygalomorphae, Theraphosidae: cryptic diversity in North American tarantulas.

    Directory of Open Access Journals (Sweden)

    Chris A Hamilton

    Full Text Available BACKGROUND: The primary objective of this study is to reconstruct the phylogeny of the hentzi species group and sister species in the North American tarantula genus, Aphonopelma, using a set of mitochondrial DNA markers that include the animal "barcoding gene". An mtDNA genealogy is used to consider questions regarding species boundary delimitation and to evaluate timing of divergence to infer historical biogeographic events that played a role in shaping the present-day diversity and distribution. We aimed to identify potential refugial locations, directionality of range expansion, and test whether A. hentzi post-glacial expansion fit a predicted time frame. METHODS AND FINDINGS: A Bayesian phylogenetic approach was used to analyze a 2051 base pair (bp mtDNA data matrix comprising aligned fragments of the gene regions CO1 (1165 bp and ND1-16S (886 bp. Multiple species delimitation techniques (DNA tree-based methods, a "barcode gap" using percent of pairwise sequence divergence (uncorrected p-distances, and the GMYC method consistently recognized a number of divergent and genealogically exclusive groups. CONCLUSIONS: The use of numerous species delimitation methods, in concert, provide an effective approach to dissecting species boundaries in this spider group; as well they seem to provide strong evidence for a number of nominal, previously undiscovered, and cryptic species. Our data also indicate that Pleistocene habitat fragmentation and subsequent range expansion events may have shaped contemporary phylogeographic patterns of Aphonopelma diversity in the southwestern United States, particularly for the A. hentzi species group. These findings indicate that future species delimitation approaches need to be analyzed in context of a number of factors, such as the sampling distribution, loci used, biogeographic history, breadth of morphological variation, ecological factors, and behavioral data, to make truly integrative decisions about what

  10. New Vistas Open with MIDI at the VLT Interferometer

    Science.gov (United States)

    2002-12-01

    "First Fringes" in Mid-Infrared Spectral Region with Two Giant Telescopes Summary Following several weeks of around-the-clock work, a team of astronomers and engineers from Germany, the Netherlands, France and ESO [2] has successfully performed the first observations with the MID-Infrared interferometric instrument (MIDI), a new, extremely powerful instrument just installed in the underground laboratory of the VLT Interferometer (VLTI) at the Paranal Observatory (Chile). In the early morning of December 15, 2002, two of the 8.2 m VLT unit telescopes (ANTU and MELIPAL) were pointed towards the southern star eta Carinae and the two light beams were directed via the complex intervening optics system towards MIDI. After a few hours of tuning and optimization, strong and stable interferometric fringes were obtained, indicating that all VLTI components - from telescopes to the new instrument - were working together perfectly. Two more stars were observed before sunrise, further proving the stability of the entire system. The first observations with MIDI mark one more important step towards full and regular operation of the VLT Interferometer [3] . They are a result of five years of determined efforts within a concerted technology project, based on a close collaboration between ESO and several European research institutes (see below). Now opening great research vistas, they also represent several "firsts" in observational astrophysics, together amounting to a real breakthrough in the field of astronomical interferometry . New views at mid-infrared wavelengths : MIDI is sensitive to light of a wavelength near 10 µm, i.e., in the mid-infrared spectral region ("thermal infrared"). This provides rich opportunities to study a wide range of otherwise inaccessible, crucial astrophysical phenomena, e.g., the formation of planets in dusty disks around newborn stars and the innermost regions around black holes. However, it is a great technical challenge to perform mid

  11. Subwoofer and nanotube butterfly acoustic flame extinction

    Science.gov (United States)

    Aliev, Ali E.; Mayo, Nathanael K.; Baughman, Ray H.; Mills, Brent T.; Habtour, Ed

    2017-07-01

    Nonchemical flame control using acoustic waves from a subwoofer and a lightweight carbon nanotube thermoacoustic projector was demonstrated. The intent was to manipulate flame intensity, direction and propagation. The mechanisms of flame suppression using low frequency acoustic waves were discussed. Laminar flame control and extinction were achieved using a thermoacoustic ‘butterfly’ projector based on freestanding carbon nanotube sheets.

  12. A VLT/FLAMES survey for massive binaries in Westerlund 1. II. Dynamical constraints on magnetar progenitor masses

    NARCIS (Netherlands)

    Ritchie, B. W.; Clark, J.S.; Negueruela, I.; Langer, N.

    2010-01-01

    Context. Westerlund 1 is a young, massive Galactic starburst cluster that contains a rich coeval population of Wolf-Rayet stars, hot- and cool-phase transitional supergiants, and a magnetar. Aims. We use spectroscopic and photometric observations of the eclipsing double-lined binary W13 to derive dy

  13. Atomic Diffusion and Mixing in Old Stars I. VLT/FLAMES-UVES Observations of Stars in NGC 6397

    CERN Document Server

    Korn, A J; Richard, O; Barklem, P S; Mashonkina, L; Collet, R; Gustafsson, B; Piskunov, N

    2007-01-01

    We present a homogeneous photometric and spectroscopic analysis of 18 stars along the evolutionary sequence of the metal-poor globular cluster NGC 6397 ([Fe/H] = -2), from the main-sequence turnoff point to red giants below the bump. The spectroscopic stellar parameters, in particular stellar-parameter differences between groups of stars, are in good agreement with broad-band and Stroemgren photometry calibrated on the infrared-flux method. The spectroscopic abundance analysis reveals, for the first time, systematic trends of iron abundance with evolutionary stage. Iron is found to be 31% less abundant in the turnoff-point stars than in the red giants. An abundance difference in lithium is seen between the turnoff-point and warm subgiant stars. The impact of potential systematic errors on these abundance trends (stellar parameters, the hydrostatic and LTE approximations) is quantitatively evaluated and found not to alter our conclusions significantly. Trends for various elements (Li, Mg, Ca, Ti and Fe) are co...

  14. The VLT Adaptive Optics Facility Project: Telescope Systems

    Science.gov (United States)

    Arsenault, Robin; Hubin, Norbert; Stroebele, Stefan; Fedrigo, Enrico; Oberti, Sylvain; Kissler-Patig, Markus; Bacon, Roland; McDermid, Richard; Bonaccini-Calia, Domenico; Biasi, Roberto; Gallieni, Daniele; Riccardi, Armando; Donaldson, Rob; Lelouarn, Miska; Hackenberg, Wolfgang; Conzelman, Ralf; Delabre, Bernard; Stuik, Remko; Paufique, Jerome; Kasper, Markus; Vernet, Elise; Downing, Mark; Esposito, Simone; Duchateau, Michel; Franx, Marijn; Myers, Richard; Goodsell, Steven

    2006-03-01

    The Adaptive Optics Facility is a project to convert UT4 into a specialised Adaptive Telescope. The present secondary mirror (M2) will be replaced by a new M2-Unit hosting a 1170-actuator deformable mirror. The three focal stations will be equipped with instruments adapted to the new capability of this UT. Two instruments have been identified for the two Nasmyth foci: Hawk-I with its AO module GRAAL allowing a Ground Layer Adaptive Optics correction and MUSE with GALACSI for GLAO correction and Laser Tomography Adaptive Optics correction. A future instrument still needs to be defined for the Cassegrain focus. Several guide stars are required for the type of adaptive corrections needed and a Four Laser Guide Star Facility (4LGSF) is being developed in the scope of the AO Facility. Convex mirrors like the VLT M2 represent a major challenge for testing and a substantial effort is dedicated to this. ASSIST, is a test bench that will allow testing of the Deformable Secondary Mirror and both instruments with simulated turbulence. This article focusses on the telescope systems (Adaptive Secondary, Four Laser Guide Star Facility, RTC platform and ASSIST Test Bench). The following article describes the AO Modules GALACSI and GRAAL.

  15. VLT polarimetry observations of PSR B0656+14

    CERN Document Server

    Mignani, R P; Shearer, A; Testa, V; Sowikowska, A; Rudak, B; Krzeszowki, K; Kanbach, G

    2015-01-01

    Optical polarisation measurements are key tests for different models of the pulsar magnetosphere. Furthermore, comparing the relative orientation of the phase-averaged linear polarisation direction and the pulsar proper motion vector may unveil a peculiar alignment, clearly seen in the Crab pulsar. Our goal is to obtain the first measurement of the phase-averaged optical linear polarisation of the fifth brightest optical pulsar, PSR\\, B0656+14, which has also a precisely measured proper motion, and verify a possible alignment between the polarisation direction and the proper motion vector. We carried out observations with the Very Large Telescope (VLT) to measure the phase-averaged optical polarisation degree (P.D.) and position angle (P.A.) of PSR B0656+14. We measured a P.D. of $11.9\\%\\pm5.5\\%$ and a P.A. of $125.8\\degr\\pm13.2\\degr$, measured East of North. Albeit of marginal significance, this is the first measurement of the phase-averaged optical P. D. for this pulsar. Moreover, we found that the P.A. of ...

  16. Astrometric precision of observations at VLT/FORS2

    CERN Document Server

    Lazorenko, P F

    2005-01-01

    In this paper we test the astrometric precision of VLT/FORS2 observations using a serie of CCD frames taken in Galactic bulge area. A special reduction method based on symmetrization of reference fields was used to reduce the atmospheric image motion. Positional precision of unsaturated R=16 mag star images at 17 sec exposure and 0.55 arcsec seeing was found to be equal to 300 microarcsec. The total error of observations was decomposed into components. It was shown that astrometric error depends largely on the photon centroiding error of the target (250 microarcsec for 16 mag stars) while the image motion is much less (110 microarcsec). At galactic latitudes to about 20 degrees, precision for a serie of frames with a 10 min total exposure is estimated to be 30-50 microarcsec for 14-16 mag stars providing the images are not overexposed and the filter R "special" is used. Error estimates for fields with smaller sky star density are given. We conclude that astrometric observations with large telescopes, under op...

  17. Sharpest Ever VLT Images at NAOS-CONICA "First Light"

    Science.gov (United States)

    2001-12-01

    Very Promising Start-Up of New Adaptive Optics Instrument at Paranal Summary A team of astronomers and engineers from French and German research institutes and ESO at the Paranal Observatory is celebrating the successful accomplishment of "First Light" for the NAOS-CONICA Adaptive Optics facility . With this event, another important milestone for the Very Large Telescope (VLT) project has been passed. Normally, the achievable image sharpness of a ground-based telescope is limited by the effect of atmospheric turbulence. However, with the Adaptive Optics (AO) technique, this drawback can be overcome and the telescope produces images that are at the theoretical limit, i.e., as sharp as if it were in space . Adaptive Optics works by means of a computer-controlled, flexible mirror that counteracts the image distortion induced by atmospheric turbulence in real time. The larger the main mirror of the telescope is, and the shorter the wavelength of the observed light, the sharper will be the images recorded. During a preceding four-week period of hard and concentrated work, the expert team assembled and installed this major astronomical instrument at the 8.2-m VLT YEPUN Unit Telescope (UT4). On November 25, 2001, following careful adjustments of this complex apparatus, a steady stream of photons from a southern star bounced off the computer-controlled deformable mirror inside NAOS and proceeded to form in CONICA the sharpest image produced so far by one of the VLT telescopes. With a core angular diameter of only 0.07 arcsec, this image is near the theoretical limit possible for a telescope of this size and at the infrared wavelength used for this demonstration (the K-band at 2.2 µm). Subsequent tests reached the spectacular performance of 0.04 arcsec in the J-band (wavelength 1.2 µm). "I am proud of this impressive achievement", says ESO Director General Catherine Cesarsky. "It shows the true potential of European science and technology and it provides a fine

  18. VLT spectroscopy of XTE J2123-058 during quiescence

    CERN Document Server

    Casares, J; Shahbaz, T; Zurita, C; Charles, P A

    2001-01-01

    We present VLT low resolution spectroscopy of the neutron star X-ray transient XTE J2123-058 during its quiescent state. Our data reveal the presence of a K7V companion which contributes 77 % to the total flux at 6300 A and orbits the neutron star at K_2 = 287 +/- 12 km/s. Contrary to other soft X-ray transients (SXTs), the Halpha emission is almost exactly in antiphase with the velocity curve of the optical companion. Using the light-center technique we obtain K_1 = 140 +/- 27 km/s and hence q=K_1/K_2=M_2/M_1= 0.49 +/- 0.10. This, combined with a previous determination of the inclination angle (i=73 +/- 4) yields M_1 = 1.55 +/- 0.31 Msun and M_2 = 0.76 +/- 0.22 Msun. M_2 agrees well with the observed spectral type. Doppler tomography of the Halpha emission shows a non-symmetric accretion disc distribution mimicking that seen in SW Sex stars. Although we find a large systemic velocity of -110 +/- 8 km/s this value is consistent with the galactic rotation velocity at the position of J2123-058, and hence a halo...

  19. Recent Advances in Flame Tomographyt

    Institute of Scientific and Technical Information of China (English)

    闫勇; 邱天; 卢钢; M.M.Hossain; G.Gilabert; 刘石

    2012-01-01

    To reduce greenhouse gas emissions from fossil fuel fired power plants,a range of new combustion technologies are being developed or refined,including oxy-fuel combustion,co-firing biomass with coal and fluidized bed combustion.Flame characteristics under such combustion conditions are expected to be different from those in normal air fired combustion processes.Quantified flame characteristics such as temperature distribution,oscillation frequency,and ignition volume play an important part in the optimized design and operation of the environmentally friendly power generation systems.However,it is challenging to obtain such flame characteristics particularly through a three-dimensional and non-intrusive means.Various tomography methods have been proposed to visualize and characterize flames,including passive optical tomography,laser based tomography,and electrical tomography.This paper identifies the challenges in flame tomography and reviews existing techniques for the quantitative characterization of flames.Future trends in flame tomography for industrial applications are discussed.

  20. Turbulence in laminar premixed V-flames

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Xiaoqian(张孝谦); LEI; Yu(雷宇); WANG; Baorui(王宝瑞); WANG; Yue(王岳); WEI; Minggang(韦明罡)

    2003-01-01

    Strong velocity fluctuations had been found in the laminar premixed V-flames. These velocity fluctuations are closely related to the chemical reaction. But the effects of the upstream combustible mixture velocity on the velocity fluctuations inside the flame are quite weak. The probability distribution function (PDF) of the velocity in the centre region of the flame appears "flat top" shaped. By analyzing the experiment results the flame-flow interactions are found to affect the flame not only at large scale in the flow field but also at small scale inside the flame. These effects will give rise to flame generated small scale turbulences.

  1. The VLT Measures the Shape of a Type Ia Supernova

    Science.gov (United States)

    2003-08-01

    First Polarimetric Detection of Explosion Asymmetry has Cosmological Implications Summary An international team of astronomers [2] has performed new and very detailed observations of a supernova in a distant galaxy with the ESO Very Large Telescope (VLT) at the Paranal Observatory (Chile). They show for the first time that a particular type of supernova, caused by the explosion of a "white dwarf", a dense star with a mass around that of the Sun, is asymmetric during the initial phases of expansion . The significance of this observation is much larger than may seem at a first glance . This particular kind of supernova, designated "Type Ia", plays a very important role in the current attempts to map the Universe. It has for long been assumed that Type Ia supernovae all have the same intrinsic brightness , earning them a nickname as "standard candles". If so, differences in the observed brightness between individual supernovae of this type simply reflect their different distances. This, and the fact that the peak brightness of these supernovae rivals that of their parent galaxy, has allowed to measure distances of even very remote galaxies . Some apparent discrepancies that were recently found have led to the discovery of cosmic acceleration . However, this first clearcut observation of explosion asymmetry in a Type Ia supernova means that the exact brightness of such an object will depend on the angle from which it is seen. Since this angle is unknown for any particular supernova, this obviously introduces an amount of uncertainty into this kind of basic distance measurements in the Universe which must be taken into account in the future. Fortunately, the VLT data also show that if you wait a little - which in observational terms makes it possible to look deeper into the expanding fireball - then it becomes more spherical. Distance determinations of supernovae that are performed at this later stage will therefore be more accurate. PR Photo 24a/03 : Spiral galaxy NGC

  2. Premixed flame propagation in vertical tubes

    CERN Document Server

    Kazakov, Kirill A

    2015-01-01

    Analytical treatment of premixed flame propagation in vertical tubes with smooth walls is given. Using the on-shell flame description, equations describing quasi-steady flame with a small but finite front thickness are obtained and solved numerically. It is found that near the limits of inflammability, solutions describing upward flame propagation come in pairs having close propagation speeds, and that the effect of gravity is to reverse the burnt gas velocity profile generated by the flame. On the basis of these results, a theory of partial flame propagation driven by the gravitational field is developed. A complete explanation is given of the intricate observed behavior of limit flames, including dependence of the inflammability range on the size of the combustion domain, the large distances of partial flame propagation, and the progression of flame extinction. The role of the finite front-thickness effects is discussed in detail. Also, various mechanisms governing flame acceleration in smooth tubes are ide...

  3. Electrical Aspects of Impinging Flames

    Science.gov (United States)

    Chien, Yu-Chien

    This dissertation examines the use of electric fields as one mechanism for controlling combustion as flames are partially extinguished when impinging on nearby surfaces. Electrical aspects of flames, specifically, the production of chemi-ions in hydrocarbon flames and the use of convective flows driven by these ions, have been investigated in a wide range of applications in prior work but despite this fairly comprehensive effort to study electrical aspects of combustion, relatively little research has focused on electrical phenomena near flame extinguishment, nor for flames near impingement surfaces. Electrical impinging flames have complex properties under global influences of ion-driven winds and flow field disturbances from the impingement surface. Challenges of measurements when an electric field is applied in the system have limited an understanding of changes to the flame behavior and species concentrations caused by the field. This research initially characterizes the ability of high voltage power supplies to respond on sufficiently short time scales to permit real time electrical flame actuation. The study then characterizes the influence of an electric field on the impinging flame shape, ion current and flow field of the thermal plume associated with the flame. The more significant further examinations can be separated into two parts: 1) the potential for using electric fields to control the release of carbon monoxide (CO) from surface-impinging flames, and 2) an investigation of controlling electrically the heat transfer to a plate on which the flame impinges. Carbon monoxide (CO) results from the incomplete oxidation of hydrocarbon fuels and, while CO can be desirable in some syngas processes, it is usually a dangerous emission from forest fires, gas heaters, gas stoves, or furnaces where insufficient oxygen in the core reaction does not fully oxidize the fuel to carbon dioxide and water. Determining how carbon monoxide is released and how heat transfer

  4. VLT Smashes the Record of the Farthest Known Galaxy

    Science.gov (United States)

    2004-03-01

    formed which could illuminate the vast space. The Universe was a cold and opaque place. This sombre era is therefore quite reasonably dubbed the "Dark Ages". A few hundred million years later, the first generation of stars and, later still, the first galaxies and quasars, produced intense ultraviolet radiation, gradually lifting the fog over the Universe. This was the end of the Dark Ages and, with a term again taken over from human history, is sometimes referred to as the "Cosmic Renaissance". Astronomers are trying to pin down when - and how - exactly the Dark Ages finished. This requires looking for the remotest objects, a challenge that only the largest telescopes, combined with a very careful observing strategy, can take up. Using a Gravitational Telescope With the advent of 8-10 meter class telescopes spectacular progress has been achieved during the last decade. Indeed it has since become possible to observe with some detail several thousand galaxies and quasars out to distances of nearly 12 billion light-years (i.e. up to a redshift of 3 [3]). In other words astronomers are now able to study individual galaxies, their formation, evolution, and other properties over typically 85 % of the past history of the Universe. Further in the past, however, observations of galaxies and quasars become scarce. Currently, only a handful of very faint galaxies are seen approximately 1,200 to 750 million years after the Big Bang (redshift 5-7). Beyond that, the faintness of these sources and the fact their light is shifted from the optical to the near infrared has so far severely limited the studies. An important breakthrough in this quest for the earliest formed galaxy has now been achieved by a team of French and Swiss astronomers [2] using ESO's Very Large Telescope (VLT) equipped with the near-infrared sensitive instrument ISAAC. To accomplish this, they had to combine the light amplification effect of a cluster of galaxies - a Gravitational Telescope - with the light

  5. VLT Captures First Direct Spectrum of an Exoplanet

    Science.gov (United States)

    2010-01-01

    eclipse", and then the spectrum could be extracted by comparing the light of the star before and after. However, this method can only be applied if the orientation of the exoplanet's orbit is exactly right, which is true for only a small fraction of all exoplanetary systems. The present spectrum, on the other hand, was obtained from the ground, using ESO's Very Large Telescope (VLT), in direct observations that do not depend on the orbit's orientation. As the host star is several thousand times brighter than the planet, this is a remarkable achievement. "It's like trying to see what a candle is made of, by observing it from a distance of two kilometres when it's next to a blindingly bright 300 Watt lamp," says Janson. The discovery was made possible by the infrared instrument NACO, mounted on the VLT, and relied heavily on the extraordinary capabilities of the instrument's adaptive optics system [3]. Even more precise images and spectra of giant exoplanets are expected both from the next generation instrument SPHERE, to be installed on the VLT in 2011, and from the European Extremely Large Telescope. The newly collected data show that the atmosphere enclosing the planet is still poorly understood. "The features observed in the spectrum are not compatible with current theoretical models," explains co-author Wolfgang Brandner. "We need to take into account a more detailed description of the atmospheric dust clouds, or accept that the atmosphere has a different chemical composition from that previously assumed." The astronomers hope to soon get their hands on the fingerprints of the other two giant planets so they can compare, for the first time, the spectra of three planets belonging to the same system. "This will surely shed new light on the processes that lead to the formation of planetary systems like our own," concludes Janson. Notes [1] As every rainbow demonstrates, white light can be split up into different colours. Astronomers artificially split up the light they

  6. Role of flame generated flow in the formation of tulip flame

    Energy Technology Data Exchange (ETDEWEB)

    Jeung, I.S.; Cho, K.K.; Jeong, K.S.

    1989-01-01

    The role of flame generated flow during the laminar 'tulip' flame formation in a long rectangular combustion vessel was examined by laser Doppler velocimeter measurement, high speed schlieren photographic flame visualization, and combustion vessel pressure measurement. Results of these investigations showed the transition of convex-shaped flame to concave-shaped tulip flame and interactions between the flame shape and flame generated flow in a confined geometry, and gave physical understanding of flow field formation of tulip flame. 15 references.

  7. Discovery of a distinct superfamily of Kunitz-type toxin (KTT from tarantulas.

    Directory of Open Access Journals (Sweden)

    Chun-Hua Yuan

    Full Text Available BACKGROUND: Kuntiz-type toxins (KTTs have been found in the venom of animals such as snake, cone snail and sea anemone. The main ancestral function of Kunitz-type proteins was the inhibition of a diverse array of serine proteases, while toxic activities (such as ion-channel blocking were developed under a variety of Darwinian selection pressures. How new functions were grafted onto an old protein scaffold and what effect Darwinian selection pressures had on KTT evolution remains a puzzle. PRINCIPAL FINDINGS: Here we report the presence of a new superfamily of ktts in spiders (TARANTULAS: Ornithoctonus huwena and Ornithoctonus hainana, which share low sequence similarity to known KTTs and is clustered in a distinct clade in the phylogenetic tree of KTT evolution. The representative molecule of spider KTTs, HWTX-XI, purified from the venom of O. huwena, is a bi-functional protein which is a very potent trypsin inhibitor (about 30-fold more strong than BPTI as well as a weak Kv1.1 potassium channel blocker. Structural analysis of HWTX-XI in 3-D by NMR together with comparative function analysis of 18 expressed mutants of this toxin revealed two separate sites, corresponding to these two activities, located on the two ends of the cone-shape molecule of HWTX-XI. Comparison of non-synonymous/synonymous mutation ratios (omega for each site in spider and snake KTTs, as well as PBTI like body Kunitz proteins revealed high Darwinian selection pressure on the binding sites for Kv channels and serine proteases in snake, while only on the proteases in spider and none detected in body proteins, suggesting different rates and patterns of evolution among them. The results also revealed a series of key events in the history of spider KTT evolution, including the formation of a novel KTT family (named sub-Kuntiz-type toxins derived from the ancestral native KTTs with the loss of the second disulfide bridge accompanied by several dramatic sequence modifications

  8. Taxonomic revision of the tarantula genus Aphonopelma Pocock, 1901 (Araneae, Mygalomorphae, Theraphosidae) within the United States.

    Science.gov (United States)

    Hamilton, Chris A; Hendrixson, Brent E; Bond, Jason E

    2016-01-01

    This systematic study documents the taxonomy, diversity, and distribution of the tarantula spider genus Aphonopelma Pocock, 1901 within the United States. By employing phylogenomic, morphological, and geospatial data, we evaluated all 55 nominal species in the United States to examine the evolutionary history of Aphonopelma and the group's taxonomy by implementing an integrative approach to species delimitation. Based on our analyses, we now recognize only 29 distinct species in the United States. We propose 33 new synonymies (Aphonopelma apacheum, Aphonopelma minchi, Aphonopelma rothi, Aphonopelma schmidti, Aphonopelma stahnkei = Aphonopelma chalcodes; Aphonopelma arnoldi = Aphonopelma armada; Aphonopelma behlei, Aphonopelma vogelae = Aphonopelma marxi; Aphonopelma breenei = Aphonopelma anax; Aphonopelma chambersi, Aphonopelma clarum, Aphonopelma cryptethum, Aphonopelma sandersoni, Aphonopelma sullivani = Aphonopelma eutylenum; Aphonopelma clarki, Aphonopelma coloradanum, Aphonopelma echinum, Aphonopelma gurleyi, Aphonopelma harlingenum, Aphonopelma odelli, Aphonopelma waconum, Aphonopelma wichitanum = Aphonopelma hentzi; Aphonopelma heterops = Aphonopelma moderatum; Aphonopelma jungi, Aphonopelma punzoi = Aphonopelma vorhiesi; Aphonopelma brunnius, Aphonopelma chamberlini, Aphonopelma iviei, Aphonopelma lithodomum, Aphonopelma smithi, Aphonopelma zionis = Aphonopelma iodius; Aphonopelma phanum, Aphonopelma reversum = Aphonopelma steindachneri), 14 new species (Aphonopelma atomicum sp. n., Aphonopelma catalina sp. n., Aphonopelma chiricahua sp. n., Aphonopelma icenoglei sp. n., Aphonopelma johnnycashi sp. n., Aphonopelma madera sp. n., Aphonopelma mareki sp. n., Aphonopelma moellendorfi sp. n., Aphonopelma parvum sp. n., Aphonopelma peloncillo sp. n., Aphonopelma prenticei sp. n., Aphonopelma saguaro sp. n., Aphonopelma superstitionense sp. n., and Aphonopelma xwalxwal sp. n.), and seven nomina dubia (Aphonopelma baergi, Aphonopelma cratium, Aphonopelma hollyi

  9. The VLT Unravels the Nature of the Fastest Binary Star

    Science.gov (United States)

    2002-03-01

    Two Hot White Dwarfs Perform a Tight Dance Summary Observations with ESO's Very Large Telescope (VLT) in Chile and the Italian Telescopio Nazionale Galileo (TNG) on the Canary Islands during the past two years have enabled an international group of astronomers [1] to unravel the true nature of an exceptional binary stellar system. This system, designated RX J0806.3+1527 , was first discovered as an X-ray source of variable brightness - once every five minutes, it "switches off" for a short moment. The new observations have shown beyond doubt that this period reflects the orbital motion of two "white dwarf" stars that revolve around each other at a distance of only 80,000 km . Each of the stars is about as large as the Earth and this is the shortest orbital period known for any binary stellar system. The VLT spectrum displays lines of ionized helium, indicating that the presence of an exceedingly hot area on one of the stars - a "hot spot" with a temperature of approx. 250,000 degrees. The system is currently in a rarely seen, transitory evolutionary state . PR Photo 10a/02 : U- and R-band images of RX J0806.3+1527. PR Photo 10b/02 : Spectrum of RX J0806.3+1527 An amazing stellar binary system ESO PR Photo 10a/02 ESO PR Photo 10a/02 [Preview - JPEG: 800 x 400 pix - 440k] [Normal - JPEG: 1600 x 800 pix - 1.1M] Caption : PR Photo 10a/02 shows U and R filter images of the sky field around RX J0806.3+1527 (at centre of circle), obtained with the FORS2 multi-mode instrument on VLT KUEYEN. The object is brightest at the shorter wavelength (U-band) - reflecting its very high temperature. Technical information about the photo is available below. One year is the time it takes the Earth to move once around the Sun, our central star. This may seem quite fast when measured on the scale of the Universe, but this is a snail's motion compared to the the speed of two recently discovered stars. They revolve around each other 100,000 times faster; one full revolution takes only 321

  10. Mechanistic aspects of ionic reactions in flames

    DEFF Research Database (Denmark)

    Egsgaard, H.; Carlsen, L.

    1993-01-01

    Some fundamentals of the ion chemistry of flames are summarized. Mechanistic aspects of ionic reactions in flames have been studied using a VG PlasmaQuad, the ICP-system being substituted by a simple quartz burner. Simple hydrocarbon flames as well as sulfur-containing flames have been investigated....... The simple hydrocarbon flames are dominated by a series of hydrocarbonic ions and, to a minor extent, protonated oxo-compounds. The introduction of sulfur to the flames leads to significant changes in the ion composition, as sulfur-containing species become dominant. The ability of the technique to study...

  11. Is more better? Sexual confusion during courtship between two sympatric and synchronic tarantulas: Acanthoscurria suina and Eupalaestrus weijenberghi

    Directory of Open Access Journals (Sweden)

    Fernando G. Costa

    2013-10-01

    Full Text Available When two similar species co-occur in time and space, strong mechanisms isolating them from each other are expected. Acanthoscurria suina Pocock, 1903 and Eupalaestrus weijenberghi (Thorell, 1894 are two sympatric and synchronic tarantulas that inhabit burrows in Uruguay's meadows. Here we test how and when reproductive isolation operates between these species. We exposed females of each species simultaneously to two males: either one male of each species, or two males of the same species. Males courted females of both species. Contrary to expectations, however, females of A. suina responded more effusively to heterospecific than to conspecific males, whereas females of E. weijenberghi only responded to conspecific males. Clasping (prelude of mating was only recorded for couples of the same species. Females of A. suina at first seem to prefer the stronger body vibrations performed by heterospecific courting males than by males of their own species.

  12. Morphological and color differences between island and mainland populations in the Mexican red rump tarantula, Brachypelma vagans.

    Science.gov (United States)

    Vilchis-Nestor, Claudia A; Machkour-M'rabet, Salima; de Los A Barriga-Sosa, Irene; Winterton, Peter; Hénaut, Yann

    2013-01-01

    The introduction of species into new ecosystems, especially in small and isolated regions such as islands, offers an excellent opportunity to answer questions of the evolutionary processes occurring in natural conditions on a scale that could never be achieved in laboratory conditions. In this study, we examined the Mexican red rump tarantula Brachypelma vagans Ausserer (Mygalomorphae: Theraphosidae), a species that was introduced to Cozumel Island, Mexico, 40 years ago. This introduction provides an exceptional model to study effects such as morphological variation between island populations and those on the mainland in open habitats facing the island. Intraspecific variation related to the color polymorphism was compared. The aim of this study was to determine the phenotypic differences between continental populations of B. vagans and the introduced population on Cozumel Island. Phenotypic difference was evaluated using two approaches: 1) comparison of the morphometric measurements of adult and juvenile individuals at the local scale and between continental and island populations, and 2) comparison of individual color polymorphism between mainland and island populations. Two locations were sampled within the continental part of the Yucatan peninsula and two on the island of Cozumel. The number of samples analyzed at each site was 30 individuals. The morphometric results showed significant differences between continental and island populations, with bigger individuals on the island. In addition, three new variations of the typical color pattern of B. vagans recorded so far were observed. This study opens the door to further investigations to elucidate the origin of the phenotypic variation of the isolated individuals on Cozumel Island. Also, the widest range of color morphs found for a tarantula species is reported.

  13. Surface composition of Europa based on VLT observations

    Science.gov (United States)

    Ligier, N.; Poulet, F.; Carter, J.

    2016-12-01

    Jupiter's moon Europa may harbor a global salty ocean under an 80-170 km thick outer layer consisting of an icy crust (Anderson et al. 1998). Meanwhile, the 10-50 My old surface, dated by cratering rates (Pappalardo et al. 1999) implies rapid surface recycling and reprocessing that could result in tectonic activity (Kattenhorn et al. 2014) and plumes (Roth et al. 2014). The surface could thus exhibit fingerprints of chemical species, as minerals characteristics of an ocean-mantle interaction and/or organics of exobiological interest, directly originating from the subglacial ocean. In order to re-investigate the composition of Europa's surface, a global mapping campaign of the satellite was performed with the near-infrared integral field spectrograph SINFONI on the Very Large Telescope (VLT) in Chile. The high spectral binning of this instrument (0.5 nm) and large signal noise ratio in comparison to previous observations are adequate to detect sharp absorptions in the wavelength range 1.45-2.45 μm. In addition, the spatially resolved spectra we obtained over five epochs nearly cover the entire surface of Europa with a pixel scale of 12.5 by 25 m.a.s ( 35 by 70 km on Europa's surface), thus permitting a global scale study. Several icy and non-icy compounds were detected and mapped at process likely engendered by the Io plasma torus, the crystalline form is found to be approximately twice as abundant as the amorphous ice based on the analysis of the 1.65 μm band. If the surface is dominated by small and mid-sized water ice grains (25-200 μm), crystalline water-ice grains exhibit spatial inhomogeneities in their distribution. The sulfuric acid hydrate distribution exhibits the typical "bullseye" feature on the trailing hemisphere. The presence of Mg-bearing chlorinated salts (chloride, chlorate, and perchlorate) is supported by linear spectral modeling of the data, while the presence of sulfate salts is challenged. The distribution of some of these species is

  14. Saturn's Doppler velocimetry wind measurements with VLT/UVES

    Science.gov (United States)

    Silva, Miguel; Mota Machado, Pedro; Luz, David; Sanchez-Lavega, Agustin; Hueso, Ricardo; Peralta, Javier

    2016-10-01

    We present Doppler wind velocity results of Saturn's zonal flow at ~0.4 mbar pressure level. Our aim is help to constrain the characterization of the equatorial jet at the referred altitude and the latitudinal variation of the zonal winds, to contribute to monitor the spatial and temporal variability in order to achieve a better understanding of the dynamics of Saturn's zonal winds, which Sánchez-Lavega et al. (2003, Nature, 423, 623) have found to have strongly changed in recent years, as the planet approached southern summer solstice.The UVES/VLT instrument has been used, which simultaneously achieves high spectral resolving power and high spatial resolution. The field has been derotated in order to have the aperture aligned perpendicularly to Saturn's rotation axis. In this configuration, spatial information in the East-West direction is preserved in a set of spectra in the direction perpendicular to dispersion.The technique of absolute accelerometry (AA, Connes, 1985, ApSS 110, 211) has been applied to the backscattered solar spectrum in order to determine the Doppler shift associated with the zonal circulation. Our measurements have been made in the wavelength range of 480-680 nm. Previously we successfully adapted this Doppler velocimetry technique for measuring winds at Venus cloud tops (Machado et al. 2012).The observations consisted of 4 blocks of 15 exposures of 90 sec, plus two shorter blocks of 9 exposures, totalling 7.3 hours of telescope time. In order to cover the whole disk the aperture has been offset by 1 arcsec in the North-South direction between consecutive exposures. Most of the northern hemisphere was covered by the rings. Saturn's diameter was 17.4 arcsec, and the slit aperture was 0.3x25 arcsec. The aperture offset between consecutive exposures was 1 arcsec. Two observations blocks of 9 exposures only covered the central part of the disk, and four others covered the whole disk. The sub-terrestrial point was at -26.1 degrees South. The

  15. Research on flame retardation of wool fibers

    Energy Technology Data Exchange (ETDEWEB)

    Enomoto, Ichiro; Ametani, Kazuo; Sawai, Takeshi (Tokyo Metropolitan Isotope Research Center (Japan))

    1990-01-01

    Flame retardant, vinyl phosphonate oligomer, was uniformly impregnated in wool fibers, and by irradiating low energy electron beam or cobalt-60 gamma ray, the flame retardation of fabrics was attempted, as the results, the following knowledges were obtained. At the rate of sticking of flame retardant lower than that in cotton fabrics, sufficient flame retarding property can be given. The flame retarding property withstands 30 times of washing. The lowering of strength due to the processing hardly arose. For the flame retardation, gamma-ray was more effective than electron beam. Since the accidents of burning clothes have occurred frequently, their flame retardation has been demanded. So far the flame retardation of cotton fabrics has been advanced, but this time the research on the flame retardation of wool fabrics was carried out by the same method. The experimental method is explained. As for the performance of the processed fabrics, the rate of sticking of the flame retardant, the efficiency of utilization, the flame retarding property, the endurance in washing and the tensile and tearing strength were examined. As the oxygen index was higher, the flame retarding property was higher, and in the case of the index being more than 27, the flame retarding property is sufficient, that is, the rate of sticking of 6% in serge and 5% in muslin. (K.I.).

  16. Role of the outer-edge flame on flame extinction in nitrogen-diluted non-premixed counterflow flames with finite burner diameters

    KAUST Repository

    Chung, Yong Ho

    2013-03-01

    This study of nitrogen-diluted non-premixed counterflow flames with finite burner diameters investigates the important role of the outer-edge flame on flame extinction through experimental and numerical analyses. It explores flame stability diagrams mapping the flame extinction response of nitrogen-diluted non-premixed counterflow flames to varying global strain rates in terms of burner diameter, burner gap, and velocity ratio. A critical nitrogen mole fraction exists beyond which the flame cannot be sustained; the critical nitrogen mole fraction versus global strain rate curves have C-shapes for various burner diameters, burner gaps, and velocity ratios. At sufficiently high strain-rate flames, these curves collapse into one curve; therefore, the flames follow the one-dimensional flame response of a typical diffusion flame. Low strain-rate flames are significantly affected by radial conductive heat loss, and therefore flame length. Three flame extinction modes are identified: flame extinction through shrinkage of the outer-edge flame with or without oscillations at the outer-edge flame prior to the extinction, and flame extinction through a flame hole at the flame center. The extinction modes are significantly affected by the behavior of the outer-edge flame. Detailed explanations are provided based on the measured flame-surface temperature and numerical evaluation of the fractional contribution of each term in the energy equation. Radial conductive heat loss at the flame edge to ambience is the main mechanism of extinction through shrinkage of the outer-edge flame in low strain-rate flames. Reduction of the burner diameter can extend the flame extinction mode by shrinking the outer-edge flame in higher strain-rate flames. © 2012 Elsevier Ltd. All rights reserved.

  17. Enhancement of turbulent flame speed of V-shaped flames in fractal-grid-generated turbulence

    NARCIS (Netherlands)

    Verbeek, A.A.; Willems, P.A.; Stoffels, G.G.M.; Geurts, B.J.; Meer, van der T.H.

    2016-01-01

    A variety of fractal grids is used to investigate how fractal-grid-generated turbulence affects the turbulent flame speed for premixed flames. The grids are placed inside a rectangular duct and a V-shaped flame is stabilized downstream of the duct, using a metal wire. This flame is characterized usi

  18. 33 CFR 154.822 - Detonation arresters, flame arresters, and flame screens.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Detonation arresters, flame arresters, and flame screens. 154.822 Section 154.822 Navigation and Navigable Waters COAST GUARD... BULK Vapor Control Systems § 154.822 Detonation arresters, flame arresters, and flame screens. (a)...

  19. Asymptotic analysis of outwardly propagating spherical flames

    Institute of Scientific and Technical Information of China (English)

    Yun-Chao Wu; Zheng Chen

    2012-01-01

    Asymptotic analysis is conducted for outwardly propagating spherical flames with large activation energy.The spherical flame structure consists of the preheat zone,reaction zone,and equilibrium zone.Analytical solutions are separately obtained in these three zones and then asymptotically matched.In the asymptotic analysis,we derive a correlation describing the spherical flame temperature and propagation speed changing with the flame radius.This correlation is compared with previous results derived in the limit of infinite value of activation energy.Based on this correlation,the properties of spherical flame propagation are investigated and the effects of Lewis number on spherical flame propagation speed and extinction stretch rate are assessed.Moreover,the accuracy and performance of different models used in the spherical flame method are examined.It is found that in order to get accurate laminar flame speed and Markstein length,non-linear models should be used.

  20. Flame Retardants Used in Flexible Polyurethane Foam

    Science.gov (United States)

    The partnership project on flame retardants in furniture seeks to update the health and environmental profiles of flame-retardant chemicals that meet fire safety standards for upholstered consumer products with polyurethane foam

  1. Firefighters and flame retardant activism.

    Science.gov (United States)

    Cordner, Alissa; Rodgers, Kathryn M; Brown, Phil; Morello-Frosch, Rachel

    2015-02-01

    In the past decade, exposure to flame retardant chemicals has become a pressing health concern and widely discussed topic of public safety for firefighters in the United States. Working through local, state, and national unions and independent health and advocacy organizations, firefighters have made important contributions to efforts to restrict the use of certain flame retardants. Firefighters are key members in advocacy coalitions dedicated to developing new environmental health regulations and reforming flammability standards to reflect the best available fire science. Their involvement has been motivated by substantiated health concerns and critiques of deceptive lobbying practices by the chemical industry. Drawing on observations and interviews with firefighters, fire safety experts, and other involved stakeholders, this article describes why firefighters are increasingly concerned about their exposure to flame retardant chemicals in consumer products, and analyzes their involvement in state and national environmental health coalitions.

  2. Droplet and Supercritical Flame Dynamics in Propulsion

    Science.gov (United States)

    2010-03-26

    In order to study the stability of a lifted jet flame by nozzle-generated vortexes, we have developed a chemical explosive mode analysis ( CEMA ) to...runaway can consequently be distinguished. CEMA of the lifted flame shows the existence of two premixed flame fronts, which are difficult to detect

  3. Premixed flame propagation in vertical tubes

    Science.gov (United States)

    Kazakov, Kirill A.

    2016-04-01

    Analytical treatment of the premixed flame propagation in vertical tubes with smooth walls is given. Using the on-shell flame description, equations for a quasi-steady flame with a small but finite front thickness are obtained and solved numerically. It is found that near the limits of inflammability, solutions describing upward flame propagation come in pairs having close propagation speeds and that the effect of gravity is to reverse the burnt gas velocity profile generated by the flame. On the basis of these results, a theory of partial flame propagation driven by a strong gravitational field is developed. A complete explanation is given of the intricate observed behavior of limit flames, including dependence of the inflammability range on the size of the combustion domain, the large distances of partial flame propagation, and the progression of flame extinction. The role of the finite front-thickness effects is discussed in detail. Also, various mechanisms governing flame acceleration in smooth tubes are identified. Acceleration of methane-air flames in open tubes is shown to be a combined effect of the hydrostatic pressure difference produced by the ambient cold air and the difference of dynamic gas pressure at the tube ends. On the other hand, a strong spontaneous acceleration of the fast methane-oxygen flames at the initial stage of their evolution in open-closed tubes is conditioned by metastability of the quasi-steady propagation regimes. An extensive comparison of the obtained results with the experimental data is made.

  4. 30 CFR 14.20 - Flame resistance.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Flame resistance. 14.20 Section 14.20 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR TESTING, EVALUATION, AND APPROVAL OF... § 14.20 Flame resistance. Conveyor belts for use in underground coal mines must be flame-resistant...

  5. Acoustic power measurements of oscillating flames

    NARCIS (Netherlands)

    Valk, M.

    1981-01-01

    The acoustic power of an oscillating flame is measured. A turbulent premixed propane/air flame is situated near a pressure antinode of a standing wave in a laboratory combustion chamber. This standing wave is generated by a piston. The fluctuating heat release of the flame will supply acoustic power

  6. Hysteresis and transition in swirling nonpremixed flames

    NARCIS (Netherlands)

    Tummers, M.J.; Hübner, A.W.; Veen, van E.H.; Hanjalic, K.; Meer, van der Th.H.

    2009-01-01

    Strongly swirling nonpremixed flames are known to exhibit a hysteresis when transiting from an attached long, sooty, yellow flame to a short lifted blue flame, and vice versa. The upward transition (by increasing the air and fuel flow rates) corresponds to a vortex breakdown, i.e. an abrupt change f

  7. Acoustic power measurements of oscillating flames

    NARCIS (Netherlands)

    Valk, M.

    1981-01-01

    The acoustic power of an oscillating flame is measured. A turbulent premixed propane/air flame is situated near a pressure antinode of a standing wave in a laboratory combustion chamber. This standing wave is generated by a piston. The fluctuating heat release of the flame will supply acoustic power

  8. Environmental Considerations for Flame Resistant Textiles

    Science.gov (United States)

    Virtually all common textiles will ignite and burn. There are mandatory and voluntary cigarette and open-flame ignition regulations to address unreasonable fire risks associated with textile products that require them to be treated with and/or contain flame retardant chemicals to make them flame res...

  9. Cars Spectroscopy of Propellant Flames

    Science.gov (United States)

    1983-11-01

    Harris, K. Aron, and J. Fendell "N2 and 00 Vibrational CARS and H2 Rotational CARS Spectroscopy of CHI/N20 Flames," Proceedings of the Nineteenth...JANNAF Combustion Meeting, CIIA Publication No. 366, 1982, p 123. 21. K. Aron, L. E. Harris, and J. Fendell , "N and CO Vibrational CARS and H2 Rotational...9 6 5 . p 3 8 4 . . . . . 23. J. Fendell , L. E, Harris, and K. Aron, "Theoretical Calculation of 11 CARS S-Branches for Propellant Flames

  10. Experimental characterization of methane inverse diffusion flame

    KAUST Repository

    Elbaz, Ayman M.

    2014-06-26

    This article presents 10-kHz images of OH-PLIF simultaneously with 2-D PIV measurements in an inverse methane diffusion flame. Under a constant fuel flow rate, the central air jet Re was varied, leading to air to fuel velocity ratio, Vr, to vary from 8.3 to 66.5. Starting from Vr = 20.7, the flame is commonly characterized by three distinct zones. The length of the lower fuel entrainment region is inversely proportional to Vr. The flames investigated resemble a string shear layer confining this zone, and converging into the second distinct region, the flame neck zone. The third region is the rest of the flame, which spreads in a jet-like manner. The inverse diffusion flames exhibit varying degrees of partial premixing, depending upon on the velocity ratio Vr, and this region of partial premixing evolves into a well-mixed reaction zone along the flame centerline. The OH distribution correlated with the changes in the mean characteristics of the flow through reduction in the local Reynolds number due to heat release. The existence of a flame suppresses or laminarizes the turbulence at early axial locations and promotes fluctuations at the flame tip for flames with Vr < 49.8. In addition, the flame jet width can be correlated to the OH distribution. In upstream regions of the flames, the breaks in OH are counterbalanced by flame closures and are governed by edge flame propagation. These local extinctions were found to occur at locations where large flow structures were impinging on the flame and are associated with a locally higher strain rate or correlated to the local high strain rates at the flame hole edges without this flow impinging. Another contributor to re-ignition was found to be growing flame kernels. As the flames approach global blow-off, these kernels become the main mechanism for re-ignition further downstream of the flames. At low Vr, laminarization within the early regions of the flame provides an effective shield, preventing the jet flow from

  11. zCOSMOS : A large VLT/VIMOS redshift survey covering 0

    NARCIS (Netherlands)

    Lilly, S. J.; Le Fevre, O.; Renzini, A.; Zamorani, G.; Scodeggio, M.; Contini, T.; Carollo, C. M.; Hasinger, G.; Kneib, J.-P.; Iovino, A.; Le Brun, V.; Maier, C.; Mainieri, V.; Mignoli, M.; Silverman, J.; Tasca, L. A. M.; Bolzonella, M.; Bongiorno, A.; Bottini, D.; Capak, P.; Caputi, K.; Cimatti, A.; Cucciati, O.; Daddi, E.; Feldmann, R.; Franzetti, P.; Garilli, B.; Guzzo, L.; Ilbert, O.; Kampczyk, P.; Kovac, K.; Lamareille, F.; Leauthaud, A.; Le Borgne, J.-F.; McCracken, H. J.; Marinoni, C.; Pello, R.; Ricciardelli, E.; Scarlata, C.; Vergani, D.; Sanders, D. B.; Schinnerer, E.; Scoville, N.; Taniguchi, Y.; Arnouts, S.; Aussel, H.; Bardelli, S.; Brusa, M.; Cappi, A.; Ciliegi, P.; Finoguenov, A.; Foucaud, S.; Franceschini, R.; Halliday, C.; Impey, C.; Knobel, C.; Koekemoer, A.; Kurk, J.; Maccagni, D.; Maddox, S.; Marano, B.; Marconi, G.; Meneux, B.; Mobasher, B.; Moreau, C.; Peacock, J. A.; Porciani, C.; Pozzetti, L.; Scaramella, R.; Schiminovich, D.; Shopbell, P.; Smail, I.; Thompson, D.; Tresse, L.; Vettolani, G.; Zanichelli, A.; Zucca, E.

    2007-01-01

    zCOSMOS is a large-redshift survey that is being undertaken in the COSMOS field using 600 hr of observation with the VIMOS spectrograph on the 8mVLT. The survey is designed to characterize the environments of COSMOS galaxies from the 100 kpc scales of galaxy groups up to the 100 Mpc scale of the cos

  12. Motion control solution for new PLC-based standard development platform for VLT instrument control systems

    Science.gov (United States)

    Popovic, D.; Brast, R.; Di Lieto, N.; Kiekebusch, M.; Knudstrup, J.; Lucuix, C.

    2014-07-01

    More than a decade ago, due to obsolescence issues, ESO initiated the design and implementation of a custom-made CANbus based motion controller (CAN-RMC) to provide, together with a tailor-made software library (motor library), the motion control capabilities for the VME platform needed for the second generation VLT/VLTI instruments. The CAN-RMC controller has been successfully used in a number of VLT instruments but it has high production costs compared to the commercial off-the-shelf (COTS) industrial solutions available on the market today. In the scope of the selection of a new PLC-based platform for the VLT instrument control systems, ESO has evaluated motion control solutions from the company Beckhoff. This paper presents the investigation, implementation and testing of the PLC/TwinCAT/EtherCAT motion controllers for DC and stepper motors and their adaptation and integration into the VLT instrumentation framework. It reports functional and performance test results for the most typical use cases of astronomical instruments like initialization sequences, tracking, switch position detections, backslash compensation, brake handling, etc. In addition, it gives an overview of the main features of TwinCAT NC/PTP, PLCopen MC, EtherCAT motion control terminals and the engineering tools like TwinCAT Scope that are integrated into the development environment and simplify software development, testing and commissioning of motorized instrument functions.

  13. The Cepheid Distance to NGC 5236 (M 83) with the VLT

    NARCIS (Netherlands)

    Thim, F.; Tammann, G. A.; Saha, A.; Dolphin, A.; Sandage, A.; Tolstoy, E.; Labhardt, L.

    2003-01-01

    Published in: Astrophys. J. 590 (2003) 256-270 citations recorded in [Science Citation Index] Abstract: Cepheids have been observed in NGC 5236 (M 83) using the ANTU (UT1) 8.2 meter telescope of the ESO VLT with FORS1. Observations over 34 epochs in V and I have been made between January 2000 and Ju

  14. OmegaCAM: the 16k × 16k Survey Camera for the VLT Survey Telescope

    NARCIS (Netherlands)

    Deul, Erik; Kuijken, Konrad; Valentijn, Edwin A.; Tyson, J. Anthony; Wolff, Sidney

    2002-01-01

    OmegaCAM, a 16k×16k-pixel wide field optical camera, and the VLT Survey Telescope (VST) that is to host it, will constitute a major sky surveying machine that becomes operational in 2004 at ESO"s Paranal Observatory. It maps one square degree of sky with 0.21 arcsec sized pixels. Both individual pro

  15. The VLT LBG Redshift Survey - I. Clustering and dynamics of ≈1000 galaxies at z≈ 3

    NARCIS (Netherlands)

    Bielby, R. M.; Shanks, T.; Weilbacher, P. M.; Infante, L.; Crighton, N. H. M.; Bornancini, C.; Bouché, N.; Héraudeau, P.; Lambas, D. G.; Lowenthal, J.; Minniti, D.; Padilla, N.; Petitjean, P.; Theuns, T.

    2011-01-01

    We present the initial imaging and spectroscopic data acquired as part of the Very Large Telescope (VLT) VIMOS Lyman-break galaxy Survey. UBR (or UBVI) imaging covers five ≈36 × 36 arcmin2 fields centred on bright z > 3 quasi-stellar objects (QSOs), allowing ≈21 000 2

  16. MOONS: a multi-object optical and near-infrared spectrograph for the VLT

    NARCIS (Netherlands)

    Cirasuolo, M.; Afonso, J.; Bender, R.; Bonifacio, P.; Evans, C.; Kaper, L.; Oliva, Ernesto; Vanzi, Leonardo; Abreu, Manuel; Atad-Ettedgui, Eli; Babusiaux, Carine; Bauer, Franz E.; Best, Philip; Bezawada, Naidu; Bryson, Ian R.; Cabral, Alexandre; Caputi, Karina; Centrone, Mauro; Chemla, Fanny; Cimatti, Andrea; Cioni, Maria-Rosa; Clementini, Gisella; Coelho, João.; Daddi, Emanuele; Dunlop, James S.; Feltzing, Sofia; Ferguson, Annette; Flores, Hector; Fontana, Adriano; Fynbo, Johan; Garilli, Bianca; Glauser, Adrian M.; Guinouard, Isabelle; Hammer, Jean-François; Hastings, Peter R.; Hess, Hans-Joachim; Ivison, Rob J.; Jagourel, Pascal; Jarvis, Matt; Kauffman, G.; Lawrence, A.; Lee, D.; Li Causi, G.; Lilly, S.; Lorenzetti, D.; Maiolino, R.; Mannucci, F.; McLure, R.; Minniti, D.; Montgomery, D.; Muschielok, B.; Nandra, K.; Navarro, R.; Norberg, P.; Origlia, L.; Padilla, N.; Peacock, J.; Pedicini, F.; Pentericci, L.; Pragt, J.; Puech, M.; Randich, S.; Renzini, A.; Ryde, N.; Rodrigues, M.; Royer, F.; Saglia, R.; Sánchez, A.; Schnetler, H.; Sobral, D.; Speziali, R.; Todd, S.; Tolstoy, E.; Torres, M.; Venema, L.; Vitali, F.; Wegner, M.; Wells, M.; Wild, V.; Wright, G.

    2012-01-01

    MOONS is a new conceptual design for a Multi-Object Optical and Near-infrared Spectrograph for the Very Large Telescope (VLT), selected by ESO for a Phase A study. The baseline design consists of ~1000 fibers deployable over a field of view of ~500 square arcmin, the largest patrol field offered by

  17. Alcohol affects video lottery terminal (VLT) gambling behaviors and cognitions differently.

    Science.gov (United States)

    Ellery, Michael; Stewart, Sherry H

    2014-03-01

    People frequently combine alcohol use and gambling. However, our understanding of the effects of alcohol on gambling behavior is limited, both in terms of what the effects are and how they occur. The effects of a moderately intoxicating dose of alcohol (i.e., a blood alcohol concentration of .06 g%) on the video lottery terminal (VLT) gambling behaviors and cognitions of community-recruited nonpathological (n = 30) and probable pathological gamblers (n = 30) were compared. Alcohol increased the rate of double up betting (i.e., choosing to play a bonus game, after a winning video poker hand, which involves trying to pick a higher ranked card than the dealer's card from among 5 face down cards) of probable pathological gamblers, but did not influence their irrational beliefs about VLT play. Alcohol maintained the irrational beliefs about VLT play of nonpathological gamblers, but did not influence their gambling behaviors. Results are consistent with a growing body of research finding that gambling cognitions have an equivocal role in explaining actual gambling behaviors. Potential mechanisms for the observed effects are discussed. Applied implications discussed include: educating regular VLT players about the effects of alcohol on irrational gambling cognitions; reconsidering policies and practices that make alcohol available where machine gambling takes place; and targeting even moderate alcohol use in the treatment of gambling problems.

  18. Athermal design of the optical tube assemblies for the ESO VLT four laser guidestar facility

    NARCIS (Netherlands)

    Henselmans, R.; Nijkerk, M.D.; Lemmen, M.H.J.; Rijnveld, N.; Kamphues, F.G.

    2011-01-01

    TNO is developing the Optical Tube Asssemblies (OTAs) for the ESO VLT Four Laser Guide Star Facility. The OTAs are Galilean 20x beam expanders, expanding a Ø15 mm input beam to a steerable Ø300 mm output beam with a wavefront quality requirement of 50 nm rms. The allowed defocus under the influence

  19. VIMOS-VLT and Spitzer observations of a radio galaxy at z=2.5

    NARCIS (Netherlands)

    Villar-Martin, M; Sanchez, SF; De Breuck, C; Peletier, R; Vernet, J; Rettura, A; Seymour, N; Humphrey, A; Stern, D; Alighieri, SD; Fosbury, R

    2006-01-01

    We present: (i) a kinematic and morphological study of the giant Ly alpha nebula associated with the radio galaxy MRC 2104-242 (z = 2.49) based on integral field spectroscopic Visible Multiobject Spectrograph (VIMOS) data from the Very Large Telescope (VLT), and (ii) a photometric study of the host

  20. Data Mining for Double Stars on VLT Survey Telescope Image Archive

    Science.gov (United States)

    Curelaru, Lucian

    2017-04-01

    The article presents a set of methods and tools used to identify and measure double stars on already existing images produced by the ESO VLT Survey Telescope in Paranal Chile. A precision analysis and a first set of measurements are included.

  1. Imaging Invisible Flames Without Additives

    Science.gov (United States)

    Weiland, Karen J.

    1996-01-01

    Image intensifiers, video cameras, and image-data-processing computers used to study combustion. Possible to view and analyze methane, hydrogen, and other flames dim or invisible to human eye and difficult to image by use of conventional photographic and video cameras.

  2. Olympic Flame Burning In Athens

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    <正>At 6:00pm March 25 (Beijing time), 2004 Athens Olympic flame was lit in Greece’s ancient sanctuary, indicating that the torch relay started.The torch relay, established at the Berlin Games in 1936, will for the first time visit all five continents

  3. Flame monitoring enhances burner management

    Energy Technology Data Exchange (ETDEWEB)

    Flynn, T.; Bailey, R.; Fuller, T.; Daw, S.; Finney, C.; Stallings, J. [Babcock & Wilcox Research Center (USA)

    2003-02-01

    A new burner monitoring and diagnostic system called Flame Doctor offers users a more precise and discriminating understanding of burner conditions. Alpha testing on Unit 4 at AmerenUE's Meramec power plant in St. Louis, MO, USA and Beta testing is underway at plants owned by Dynegy and Allegheny Energy. 6 refs., 3 figs.

  4. VLT multi-object spectroscopy of 33 eclipsing binaries in the Small Magellanic Cloud. New distance and depth of the SMC, and a record-breaking apsidal motion

    CERN Document Server

    North, P L; Barblan, F; Royer, F

    2010-01-01

    Aim: Our purpose is to provide reliable stellar parameters for a significant sample of eclipsing binaries, which are representative of a whole dwarf and metal-poor galaxy. We also aim at providing a new estimate of the mean distance to the SMC and of its depth along the line of sight for the observed field of view. Method: We use radial velocity curves obtained with the ESO FLAMES facility at the VLT and light curves from the OGLE-II photometric survey. The radial velocities were obtained by least-squares fits of the observed spectra to synthetic ones, excluding the hydrogen Balmer lines. Results: Our sample contains 23 detached, 9 semi-detached and 1 overcontact systems. Most detached systems have properties consistent with stellar evolution calculations from single-star models at the standard SMC metallicity Z = 0.004, though they tend to be slightly overluminous. The few exceptions are probably due to third light contribution or insufficient signal-to-noise ratio. The mass ratios are consistent with a flat...

  5. Enhancements of Impinging Flame by Pulsation

    Institute of Scientific and Technical Information of China (English)

    AySu; Ying-ChiehLiu

    2000-01-01

    Experimental investigations on the pulsating jet-impinging diffusion flame were executed.A soleoid valve was aligned upstream of the jet orifice and the methane fuel was controlled in open-closed cycles from 0 Hz to 20Hz.Results show that the open-closed cycles,indeed increase the fluctuations of the methane fuel obviously.The evolutions of pulsating flame therefore develop faster than the continuous impinging flame.The optimized pulating frequencies are near 9 to 11 hz from the Re=170 to 283.The temperature differences between that under optimized pulsating rate and full open condition(no pulsation)are ranging from 100 to 150 degree.The pulsating effect is more singnificant at low Reynolds number.The cross section of continuous impinging flame behaves as elliptic shape with axial ratio equals to 2/3.The tip of the impinging flame obviously crosses at 42mm above the impinging point.ecause of the phenomenon of pulsation flame,the flame sheet or flame front may not be identified clearly in the averaged temperature contours.Results shows that the averaged end-contour of pulsation flame rears at 38mm above the impinging point.By observation and experiment,the pulsating flame behaves more stable and efficient than the continuous impinging flame.

  6. Turbulent Oxygen Flames in Type Ia Supernovae

    CERN Document Server

    Aspden, A J; Woosley, S E; 10.1088/0004-637X/730/2/144

    2011-01-01

    In previous studies, we examined turbulence-flame interactions in carbon-burning thermonuclear flames in Type Ia supernovae. In this study, we consider turbulence-flame interactions in the trailing oxygen flames. The two aims of the paper are to examine the response of the inductive oxygen flame to intense levels of turbulence, and to explore the possibility of transition to detonation in the oxygen flame. Scaling arguments analogous to the carbon flames are presented and then compared against three-dimensional simulations for a range of Damk\\"ohler numbers ($\\Da_{16}$) at a fixed Karlovitz number. The simulations suggest that turbulence does not significantly affect the oxygen flame when $\\Da_{16}1$, turbulence enhances heat transfer and drives the propagation of a flame that is {\\em narrower} than the corresponding inductive flame would be. Furthermore, burning under these conditions appears to occur as part of a combined carbon-oxygen turbulent flame with complex compound structure. The simulations do not ...

  7. Sooting limit of a double diffusion flame

    Energy Technology Data Exchange (ETDEWEB)

    Kitano, Michio; Kobayashi, Hideaki; Nishiki, Nobuhiko (Tohoku Univ., Faculty of Engineering, Sendai, Japan Sony Corp., Tokyo (Japan))

    1989-07-25

    The soot exhaust from the flame of pot type burner for the domestic heating use was basically studied. Inside a fuel (secondary) diffusion flame in air atmosphere, which was an ordinary diffusion flame, an air (primary) diffusion flame in fuel atmosphere, which was reverse in relation between them, was formed by using propane fuel. For the sooting limit of that double diffusion flame, the effect of primary air ratio, distance between primary and secondary flames, thermal condition on wall surface and flow stretch being investigated by use of three different types of burner, the double diffusion flame method was studied in effectiveness on the soot exhaust and known to heighten the control against it, which heightening however depended in degree upon the locative relation between both the flames. The control was more heightened with a more lengthening in the secondary flame. Because the sooting limit is governed by the secondary flame temperature, the establishment of condition so as to heighten the flame temperature is necessary for the effective control against the soot exhaust. 11 refs., 11 figs.

  8. Flame Reconstruction Using Synthetic Aperture Imaging

    CERN Document Server

    Murray, Preston; Tree, Dale; Truscott, Tadd

    2011-01-01

    Flames can be formed by burning methane (CH4). When oxygen is scarce, carbon particles nucleate into solid particles called soot. These particles emit photons, making the flame yellow. Later, methane is pre-mixed with air forming a blue flame; burning more efficiently, providing less soot and light. Imaging flames and knowing their temperature are vital to maximizing efficiency and validating numerical models. Most temperature probes disrupt the flame and create differences leading to an inaccurate measurement of the flame temperature. We seek to image the flame in three dimensions using synthetic aperture imaging. This technique has already successfully measured velocity fields of a vortex ring [1]. Synthetic aperture imaging is a technique that views one scene from multiple cameras set at different angles, allowing some cameras to view objects that are obscured by others. As the resulting images are overlapped different depths of the scene come into and out of focus, known as focal planes, similar to tomogr...

  9. Flex-flame burner and combustion method

    Science.gov (United States)

    Soupos, Vasilios; Zelepouga, Serguei; Rue, David M.; Abbasi, Hamid A.

    2010-08-24

    A combustion method and apparatus which produce a hybrid flame for heating metals and metal alloys, which hybrid flame has the characteristic of having an oxidant-lean portion proximate the metal or metal alloy and having an oxidant-rich portion disposed above the oxidant lean portion. This hybrid flame is produced by introducing fuel and primary combustion oxidant into the furnace chamber containing the metal or metal alloy in a substoichiometric ratio to produce a fuel-rich flame and by introducing a secondary combustion oxidant into the furnace chamber above the fuel-rich flame in a manner whereby mixing of the secondary combustion oxidant with the fuel-rich flame is delayed for a portion of the length of the flame.

  10. The discrete regime of flame propagation

    Science.gov (United States)

    Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew

    The propagation of laminar dust flames in iron dust clouds was studied in a low-gravity envi-ronment on-board a parabolic flight aircraft. The elimination of buoyancy-induced convection and particle settling permitted measurements of fundamental combustion parameters such as the burning velocity and the flame quenching distance over a wide range of particle sizes and in different gaseous mixtures. The discrete regime of flame propagation was observed by substitut-ing nitrogen present in air with xenon, an inert gas with a significantly lower heat conductivity. Flame propagation in the discrete regime is controlled by the heat transfer between neighbor-ing particles, rather than by the particle burning rate used by traditional continuum models of heterogeneous flames. The propagation mechanism of discrete flames depends on the spa-tial distribution of particles, and thus such flames are strongly influenced by local fluctuations in the fuel concentration. Constant pressure laminar dust flames were observed inside 70 cm long, 5 cm diameter Pyrex tubes. Equally-spaced plate assemblies forming rectangular chan-nels were placed inside each tube to determine the quenching distance defined as the minimum channel width through which a flame can successfully propagate. High-speed video cameras were used to measure the flame speed and a fiber optic spectrometer was used to measure the flame temperature. Experimental results were compared with predictions obtained from a numerical model of a three-dimensional flame developed to capture both the discrete nature and the random distribution of particles in the flame. Though good qualitative agreement was obtained between model predictions and experimental observations, residual g-jitters and the short reduced-gravity periods prevented further investigations of propagation limits in the dis-crete regime. The full exploration of the discrete flame phenomenon would require high-quality, long duration reduced gravity environment

  11. A flame particle tracking analysis of turbulence–chemistry interaction in hydrogen–air premixed flames

    KAUST Repository

    Uranakara, Harshavardhana A.

    2015-11-21

    Interactions of turbulence, molecular transport, and energy transport, coupled with chemistry play a crucial role in the evolution of flame surface geometry, propagation, annihilation, and local extinction/re-ignition characteristics of intensely turbulent premixed flames. This study seeks to understand how these interactions affect flame surface annihilation of lean hydrogen–air premixed turbulent flames. Direct numerical simulations (DNSs) are conducted at different parametric conditions with a detailed reaction mechanism and transport properties for hydrogen–air flames. Flame particle tracking (FPT) technique is used to follow specific flame surface segments. An analytical expression for the local displacement flame speed (Sd) of a temperature isosurface is considered, and the contributions of transport, chemistry, and kinematics on the displacement flame speed at different turbulence-flame interaction conditions are identified. In general, the displacement flame speed for the flame particles is found to increase with time for all conditions considered. This is because, eventually all flame surfaces and their resident flame particles approach annihilation by reactant island formation at the end of stretching and folding processes induced by turbulence. Statistics of principal curvature evolving in time, obtained using FPT, suggest that these islands are ellipsoidal on average enclosing fresh reactants. Further examinations show that the increase in Sd is caused by the increased negative curvature of the flame surface and eventual homogenization of temperature gradients as these reactant islands shrink due to flame propagation and turbulent mixing. Finally, the evolution of the normalized, averaged, displacement flame speed vs. stretch Karlovitz number are found to collapse on a narrow band, suggesting that a unified description of flame speed dependence on stretch rate may be possible in the Lagrangian description.

  12. Numerical simulation of tulip flame dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Cloutman, L.D.

    1991-11-30

    A finite difference reactive flow hydrodynamics program based on the full Navier-Stokes equations was used to simulate the combustion process in a homogeneous-charge, constant-volume combustion bomb in which an oddly shaped flame, known as a ``tulip flame`` in the literature, occurred. The ``tulip flame`` was readily reproduced in the numerical simulations, producing good agreement with the experimental flame shapes and positions at various times. The calculations provide sufficient detail about the dynamics of the experiment to provide some insight into the physical mechanisms responsible for the peculiar flame shape. Several factors seem to contribute to the tulip formation. The most important process is the baroclinic production of vorticity by the flame front, and this rate of production appears to be dramatically increased by the nonaxial flow generated when the initial semicircular flame front burns out along the sides of the chamber. The vorticity produces a pair of vortices behind the flame that advects the flame into the tulip shape. Boundary layer effects contribute to the details of the flame shape next to the walls of the chamber, but are otherwise not important. 24 refs.

  13. Numerical simulation of tulip flame dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Cloutman, L.D.

    1991-11-30

    A finite difference reactive flow hydrodynamics program based on the full Navier-Stokes equations was used to simulate the combustion process in a homogeneous-charge, constant-volume combustion bomb in which an oddly shaped flame, known as a tulip flame'' in the literature, occurred. The tulip flame'' was readily reproduced in the numerical simulations, producing good agreement with the experimental flame shapes and positions at various times. The calculations provide sufficient detail about the dynamics of the experiment to provide some insight into the physical mechanisms responsible for the peculiar flame shape. Several factors seem to contribute to the tulip formation. The most important process is the baroclinic production of vorticity by the flame front, and this rate of production appears to be dramatically increased by the nonaxial flow generated when the initial semicircular flame front burns out along the sides of the chamber. The vorticity produces a pair of vortices behind the flame that advects the flame into the tulip shape. Boundary layer effects contribute to the details of the flame shape next to the walls of the chamber, but are otherwise not important. 24 refs.

  14. The initial development of a tulip flame

    Energy Technology Data Exchange (ETDEWEB)

    Matalon, M.; Mcgreevy, J.L. [Northwestern Univ., Evanston, IL (United States)

    1994-12-31

    The initial development of a ``tulip flame``, often observed during flame propagation in closed tubes, is attributed to a combustion instability. The roles of hydrodynamic and of the diffusional-thermal processes on the onset of instability are investigated through a linear stability analysis in which the growth or decay of small disturbances, superimposed on an otherwise smooth and planar flame front, are followed. A range of the Markstein parameter, related to the mixture composition through an appropriately defined Lewis number, has been identified where a tulip flame could be observed. For a given value of the Markstein parameter within this range, a critical wavelength is identified as the most unstable mode. This wavelength is directly related to the minimal aspect ratio of the tube where a tulip flame could be observed. The time of onset of instability is identified as the time when the most unstable disturbance, associated with the critical wavelength, grows at a faster rate than the flame front itself and exceeds a certain threshold. This occurs after the flame has propagated a certain distance down the tube: a value which has been explicitly determined in terms of the relevant parameters. Experimental records on the tulip flame phenomenon support the finding of the analysis. That is, the tulip flame forms after the flame has traveled half the tube`s length, it does not form in short tubes, and its formation depends on the mixture composition and on the initial pressure in the tube.

  15. Chemical abundances in the protoplanetary disc LV 2 (Orion) - II. High-dispersion VLT observations and microjet properties

    Science.gov (United States)

    Tsamis, Y. G.; Walsh, J. R.

    2011-11-01

    Integral field spectroscopy of the LV 2 proplyd is presented taken with the Very Large Telescope (VLT)/FLAMES Argus array at an angular resolution of 0.31 × 0.31 arcsec2 and velocity resolutions down to 2 km s-1 pixel-1. Following subtraction of the local M42 emission, the spectrum of LV 2 is isolated from the surrounding nebula. We measured the heliocentric velocities and widths of a number of lines detected in the intrinsic spectrum of the proplyd, as well as in the adjacent Orion nebula falling within a 6.6 × 4.2 arcsec2 field of view. It is found that far-ultraviolet to optical collisional lines with critical densities, Ncr, ranging from 103 to 109 cm-3 suffer collisional de-excitation near the rest velocity of the proplyd correlating tightly with their critical densities. Lines of low Ncr are suppressed the most. The bipolar jet arising from LV 2 is spectrally and spatially well detected in several emission lines. We compute the [O III] electron temperature profile across LV 2 in velocity space and measure steep temperature variations associated with the red-shifted lobe of the jet, possibly being due to a shock discontinuity. From the velocity-resolved analysis the ionized gas near the rest frame of LV 2 has Te= 9200 ± 800 K and Ne˜ 106 cm-3, while the red-shifted jet lobe has Te≈ 9000-104 K and Ne˜ 106-107 cm-3. The jet flow is highly ionized but contains dense semineutral clumps emitting neutral oxygen lines. The abundances of N+, O2 +, Ne2 +, Fe2 +, S+and S2 +are measured for the strong red-shifted jet lobe. Iron in the core of LV 2 is depleted by 2.54 dex with respect to solar as a result of sedimentation on dust, whereas the efficient destruction of dust grains in the fast microjet raises its Fe abundance to at least 30 per cent solar. Sulphur does not show evidence of significant depletion on dust, but its abundance both in the core and the jet is only about half solar. Based on observations made with ESO telescopes at the Paranal Observatory

  16. Flame Propagation Through Concentration Gradient

    Institute of Scientific and Technical Information of China (English)

    JunyaIINO; MitsuakiTANABE; 等

    2000-01-01

    The experiment was carried out in homogeneous propane-air mixture and in several concentration gradient of mixture.Igniter is put on the upper side of the combustion chamber,In concentration gradient experiment.ixture was ignited from lean side.An experimental study was conducted in a combustion chamber.The combustion chamber has glass windows for optical measurements at any side.For the measurement of distribution of fuel concentration,infraed absorption method using 3.39μm He-Ne laser was used,and for the observation of proagating flams,Schlieren method was employed.As a measurment result of flame propagation velocity and flammable limit,for a mixture of an identical local equivalence ratio.flame propagation velocity in concentration gradient is faster than that in homogeneous mixture,and rich flammable limit in concentration gradient shows a tendency to be higher than that in homogeneous mixture.

  17. Hubble Tarantula Treasury Project. II. The Star-formation History of the Starburst Region NGC 2070 in 30 Doradus

    Science.gov (United States)

    Cignoni, M.; Sabbi, E.; van der Marel, R. P.; Tosi, M.; Zaritsky, D.; Anderson, J.; Lennon, D. J.; Aloisi, A.; de Marchi, G.; Gouliermis, D. A.; Grebel, E. K.; Smith, L. J.; Zeidler, P.

    2015-10-01

    We present a study of the recent star formation (SF) of 30 Doradus in the Large Magellanic Cloud (LMC) using the panchromatic imaging survey Hubble Tarantula Treasury Project. In this paper we focus on the stars within 20 pc of the center of 30 Doradus, the starburst region NGC 2070. We recovered the SF history by comparing deep optical and near-infrared color-magnitude diagrams (CMDs) with state-of-the-art synthetic CMDs generated with the latest PAdova and TRieste Stellar Evolution Code (PARSEC) models, which include all stellar phases from pre-main-sequence to post-main-sequence. For the first time in this region we are able to measure the SF using intermediate- and low-mass stars simultaneously. Our results suggest that NGC 2070 experienced prolonged activity. In particular, we find that the SF in the region (1) exceeded the average LMC rate ≈ 20 Myr ago, (2) accelerated dramatically ≈ 7 Myr ago, and (3) reached a peak value 1-3 Myr ago. We did not find significant deviations from a Kroupa initial mass function down to 0.5 {M}⊙ . The average internal reddening E(B-V) is found to be between 0.3 and 0.4 mag. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555.

  18. The Interaction of High-Speed Turbulence with Flames: Global Properties and Internal Flame Structure

    CERN Document Server

    Poludnenko, Alexei Y; 10.1016/j.combustflame.2009.11.018

    2011-01-01

    We study the dynamics and properties of a turbulent flame, formed in the presence of subsonic, high-speed, homogeneous, isotropic Kolmogorov-type turbulence in an unconfined system. Direct numerical simulations are performed with Athena-RFX, a massively parallel, fully compressible, high-order, dimensionally unsplit, reactive-flow code. A simplified reaction-diffusion model represents a stoichiometric H2-air mixture. The system being modeled represents turbulent combustion with the Damkohler number Da = 0.05 and with the turbulent velocity at the energy injection scale 30 times larger than the laminar flame speed. The simulations show that flame interaction with high-speed turbulence forms a steadily propagating turbulent flame with a flame brush width approximately twice the energy injection scale and a speed four times the laminar flame speed. A method for reconstructing the internal flame structure is described and used to show that the turbulent flame consists of tightly folded flamelets. The reaction zon...

  19. Heat and mass transfer in flames

    Science.gov (United States)

    Faeth, G. M.

    1986-01-01

    Heat- and mass-transfer processes in turbulent diffusion flames are discussed, considering turbulent mixing and the structure of single-phase flames, drop processes in spray flames, and nonluminous and luminous flame radiation. Interactions between turbulence and other phenomena are emphasized, concentrating on past work of the author and his associates. The conserved-scalar formalism, along with the laminar-flamelet approximation, is shown to provide reasonable estimates of the structure of gas flames, with modest levels of empiricism. Extending this approach to spray flames has highlighted the importance of drop/turbulence interactions; e.g., turbulent dispersion of drops, modification of turbulence by drops, etc. Stochastic methods being developed to treat these phenomena are yielding encouraging results.

  20. Estimating phase errors from pupil discontinuities from simulated on sky data: examples with VLT and Keck

    Science.gov (United States)

    Lamb, Masen; Correia, Carlos; Sauvage, Jean-François; Véran, Jean-Pierre; Andersen, David; Vigan, Arthur; Wizinowich, Peter; van Dam, Marcos; Mugnier, Laurent; Bond, Charlotte

    2016-07-01

    We propose and apply two methods for estimating phase discontinuities for two realistic scenarios on VLT and Keck. The methods use both phase diversity and a form of image sharpening. For the case of VLT, we simulate the `low wind effect' (LWE) which is responsible for focal plane errors in low wind and good seeing conditions. We successfully estimate the LWE using both methods, and show that using both methods both independently and together yields promising results. We also show the use of single image phase diversity in the LWE estimation, and show that it too yields promising results. Finally, we simulate segmented piston effects on Keck/NIRC2 images and successfully recover the induced phase errors using single image phase diversity. We also show that on Keck we can estimate both the segmented piston errors and any Zernike modes affiliated with the non-common path.

  1. Flame Suppression Agent, System and Uses

    Science.gov (United States)

    Parrish, Clyde F. (Inventor)

    2013-01-01

    Aqueous droplets encapsulated in a flame retardant polymer are useful in suppressing combustion. Upon exposure to a flame, the encapsulated aqueous droplets rupture and vaporize, removing heat and displacing oxygen to retard the combustion process. The polymer encapsulant, through decomposition, may further add free radicals to the combustion atmosphere, thereby further retarding the combustion process. The encapsulated aqueous droplets may be used as a replacement to halon, water mist and dry powder flame suppression systems.

  2. Effects of a Video Lottery Terminal (VLT) Banner on Gambling: A Field Study

    Science.gov (United States)

    Gallagher, Timothy; Nicki, Richard; Otteson, Amy; Elliott, Heather

    2011-01-01

    The effects of a warning banner, informing patrons of the randomness of Video Lottery Terminal (VLT) outcomes, on gambling behaviour and beliefs were tested in a field setting using a mixed-model 2 x 3 design over a six-week period with 27 problem and 27 non-problem gamblers recruited from bars in a Canadian city with a population of 85,000.…

  3. Velocity fields of distant galaxies with FORS2 at the VLT

    CERN Document Server

    Ziegler, Bodo L; Da Rocha, Cristiano; Böhm, Asmus; Kapferer, Wolfgang; Kuntschner, Harald; Peletier, Reynier F; Schindler, Sabine; Verdugo, Miguel

    2009-01-01

    We describe a method to efficiently obtain two-dimensional velocity fields of distant, faint and small, emission-line galaxies with FORS2 at the VLT. They are examined for kinematic substructure to identify possible interaction processes. Numerical simulations of tidal interactions and ram-pressure effects reveal distinct signatures observable with our method. We detect a significant fraction of galaxies with irregular velocity fields both in the field and cluster environments.

  4. Comparative Analysis of Flame Characteristics of Castor Oil and ...

    African Journals Online (AJOL)

    Flame Retardants Used in Polyurethane Foam Systems. Polycarp .O. Ikeh ... such as ignition time, flame propagation rate, after glow, char rate, add-on and glow time. These properties .... hours before the flame test to ensure complete curing.

  5. MOONS: a Multi-Object Optical and Near-infrared Spectrograph for the VLT

    CERN Document Server

    Cirasuolo, M; Bender, R; Bonifacio, P; Evans, C; Kaper, L; Oliva, E; Vanzi, L; Abreu, M; Atad-Ettedgui, E; Babusiaux, C; Bauer, F; Best, P; Bezawada, N; Bryson, I; Cabral, A; Caputi, K; Centrone, M; Chemla, F; Cimatti, A; Cioni, M-R; Clementini, G; Coelho, J; Daddi, E; Dunlop, J; Feltzing, S; Ferguson, A; Flores, H; Fontana, A; Fynbo, J; Garilli, B; Glauser, A; Guinouard, I; Hammer, F; Hastings, P; Hess, A; Ivison, R; Jagourel, P; Jarvis, M; Kauffman, G; Lawrence, A; Lee, D; Licausi, G; Lilly, S; Lorenzetti, D; Maiolino, R; Mannucci, F; McLure, R; Minniti, D; Montgomery, D; Muschielok, B; Nandra, K; Navarro, R; Norberg, P; Origlia, L; Padilla, N; Peacock, J; Pedicini, F; Pentericci, L; Pragt, J; Puech, M; Randich, S; Renzini, A; Ryde, N; Rodrigues, M; Royer, F; Saglia, R; Sanchez, A; Schnetler, H; Sobral, D; Speziali, R; Todd, S; Tolstoy, E; Torres, M; Venema, L; Vitali, F; Wegner, M; Wells, M; Wild, V; Wright, G

    2012-01-01

    MOONS is a new conceptual design for a Multi-Object Optical and Near-infrared Spectrograph for the Very Large Telescope (VLT), selected by ESO for a Phase A study. The baseline design consists of 1000 fibers deployable over a field of view of 500 square arcmin, the largest patrol field offered by the Nasmyth focus at the VLT. The total wavelength coverage is 0.8um-1.8um and two resolution modes: medium resolution and high resolution. In the medium resolution mode (R=4,000-6,000) the entire wavelength range 0.8um-1.8um is observed simultaneously, while the high resolution mode covers simultaneously three selected spectral regions: one around the CaII triplet (at R=8,000) to measure radial velocities, and two regions at R=20,000 one in the J-band and one in the H-band, for detailed measurements of chemical abundances. The grasp of the 8.2m Very Large Telescope (VLT) combined with the large multiplex and wavelength coverage of MOONS - extending into the near-IR - will provide the observational power necessary to...

  6. A valiant little terminal: A VLT user`s manual. Revision 4

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, A.

    1992-08-01

    VLT came to be used at SLAC (Stanford Linear Accelerator Center), because SLAC wanted to assess the Amiga`s usefulness as a color graphics terminal and T{sub E}X workstation. Before the project could really begin, the people at SLAC needed a terminal emulator which could successfully talk to the IBM 3081 (now the IBM ES9000-580) and all the VAXes on the site. Moreover, it had to compete in quality with the Ann Arbor Ambassador GXL terminals which were already in use at the laboratory. Unfortunately, at the time there was no commercial program which fit the bill. Luckily, Willy Langeveld had been independently hacking up a public domain VT100 emulator written by Dave Wecker et al. and the result, VLT, suited SLAC`s purpose. Over the years, as the program was debugged and rewritten, the original code disappeared, so that now, in the present version of VLT, none of the original VT100 code remains.

  7. A valiant little terminal: A VLT user's manual

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, A.

    1992-08-01

    VLT came to be used at SLAC (Stanford Linear Accelerator Center), because SLAC wanted to assess the Amiga's usefulness as a color graphics terminal and T{sub E}X workstation. Before the project could really begin, the people at SLAC needed a terminal emulator which could successfully talk to the IBM 3081 (now the IBM ES9000-580) and all the VAXes on the site. Moreover, it had to compete in quality with the Ann Arbor Ambassador GXL terminals which were already in use at the laboratory. Unfortunately, at the time there was no commercial program which fit the bill. Luckily, Willy Langeveld had been independently hacking up a public domain VT100 emulator written by Dave Wecker et al. and the result, VLT, suited SLAC's purpose. Over the years, as the program was debugged and rewritten, the original code disappeared, so that now, in the present version of VLT, none of the original VT100 code remains.

  8. Pole solutions for flame front propagation

    CERN Document Server

    Kupervasser, Oleg

    2015-01-01

    This book deals with solving mathematically the unsteady flame propagation equations. New original mathematical methods for solving complex non-linear equations and investigating their properties are presented. Pole solutions for flame front propagation are developed. Premixed flames and filtration combustion have remarkable properties: the complex nonlinear integro-differential equations for these problems have exact analytical solutions described by the motion of poles in a complex plane. Instead of complex equations, a finite set of ordinary differential equations is applied. These solutions help to investigate analytically and numerically properties of the flame front propagation equations.

  9. Soot zone structure and sooting limit in diffusion flames: Comparison of counterflow and co-flow flames

    Energy Technology Data Exchange (ETDEWEB)

    Kang, K.T.; Hwang, J.Y.; Chung, S.H. [Seoul National Univ. (Korea, Republic of). Dept. of Mechanical Engineering; Lee, W. [Dankook Univ., Seoul (Korea, Republic of). Dept. of Mechanical Engineering

    1997-04-01

    Soot zone structures of counterflow and co-flow diffusion flames have been studied experimentally using the soot extinction-scattering, polycyclic aromatic hydrocarbon fluorescence, and laser Doppler velocimetry measurements. The counterflow flame has been numerically modelled with detailed chemistry. Results show that two different categories of sooting flame structures can be classified depending on the relative transport of soot particles to flames. These are the soot formation-oxidation flame and the soot formation flame. The soot formation-oxidation flame characteristics are observed in counterflow flames when located on the fuel side and in normal co-flow flames. In this case, soot particles are transported toward the high temperature region or the flame and experience soot inception, coagulation-growth, and oxidation. The soot formation flame characteristics are observed in counterflow flames when located on the oxidizer side and in inverse co-flow flames. In this case, soot particles are transported away from the flame without experiencing oxidation and finally leak through the stagnation plane in counterflow flames or leave the flame in inverse co-flow flames. Sooting limit measurements in both flames also substantiate the two different sooting flame structures and their characteristics.

  10. Flame dynamics of a meso-scale heat recirculating combustor

    Energy Technology Data Exchange (ETDEWEB)

    Vijayan, V.; Gupta, A.K. [Department of Mechanical Engineering, University of Maryland, College Park, MD 20742 (United States)

    2010-12-15

    The dynamics of premixed propane-air flame in a meso-scale ceramic combustor has been examined here. The flame characteristics in the combustor were examined by measuring the acoustic emissions and preheat temperatures together with high-speed cinematography. For the small-scale combustor, the volume to surface area ratio is small and hence the walls have significant effect on the global flame structure, flame location and flame dynamics. In addition to the flame-wall thermal coupling there is a coupling between flame and acoustics in the case of confined flames. Flame-wall thermal interactions lead to low frequency flame fluctuations ({proportional_to}100 Hz) depending upon the thermal response of the wall. However, the flame-acoustic interactions can result in a wide range of flame fluctuations ranging from few hundred Hz to few kHz. Wall temperature distribution is one of the factors that control the amount of reactant preheating which in turn effects the location of flame stabilization. Acoustic emission signals and high-speed flame imaging confirmed that for the present case flame-acoustic interactions have more significant effect on flame dynamics. Based on the acoustic emissions, five different flame regimes have been identified; whistling/harmonic mode, rich instability mode, lean instability mode, silent mode and pulsating flame mode. (author)

  11. Unsteady planar diffusion flames: Ignition, travel, burnout

    Science.gov (United States)

    Fendell, F.; Wu, F.

    1995-01-01

    In microgravity, a thin planar diffusion flame is created and thenceforth travels so that the flame is situated at all times at an interface at which the hydrogen and oxygen meet in stoichiometric proportion. If the initial amount of hydrogen is deficient relative to the initial amount of oxygen, then the planar flame will travel further and further into the half volume initially containing hydrogen, until the hydrogen is (virtually) fully depleted. Of course, when the amount of residual hydrogen becomes small, the diffusion flame is neither vigorous nor thin; in practice, the flame is extinguished before the hydrogen is fully depleted, owing to the finite rate of the actual chemical-kinetic mechanism. The rate of travel of the hydrogen-air diffusion flame is much slower than the rate of laminar flame propagation through a hydrogen-air mixture. This slow travel facilitates diagnostic detection of the flame position as a function of time, but the slow travel also means that the time to burnout (extinction) probably far exceeds the testing time (typically, a few seconds) available in earth-sited facilities for microgravity-environment experiments. We undertake an analysis to predict (1) the position and temperature of the diffusion flame as a function of time, (2) the time at which extinction of the diffusion flame occurs, and (3) the thickness of quench layers formed on side walls (i.e., on lateral boundaries, with normal vectors parallel to the diffusion-flame plane), and whether, prior to extinction, water vapor formed by burning will condense on these cold walls.

  12. Tulip flames: changes in shape of premixed flames propagating in closed tubes

    Science.gov (United States)

    Dunn-Rankin, D.; Sawyer, R. F.

    The experimental results that are the subject of this communication provide high-speed schlieren images of the closed-tube flame shape that has come to be known as the tulip flame. The schlieren images, along with in-chamber pressure records, help demonstrate the effects of chamber length, equivalence ratio, and igniter geometry on formation of the tulip flame. The pressure/time records show distinct features which correlate with flame shape changes during the transition to tulip. The measurements indicate that the basic tulip flame formation is a robust phenomenon that depends on little except the overall geometry of the combustion vessel.

  13. Impact of flame-wall interaction on premixed flame dynamics and transfer function characteristics

    KAUST Repository

    Kedia, K.S.

    2011-01-01

    In this paper, we numerically investigate the response of a perforated-plate stabilized laminar methane-air premixed flame to imposed inlet velocity perturbations. A flame model using detailed chemical kinetics mechanism is applied and heat exchange between the burner plate and the gas mixture is incorporated. Linear transfer functions, for low mean inlet velocity oscillations, are analyzed for different equivalence ratio, mean inlet velocity, plate thermal conductivity and distance between adjacent holes. The oscillations of the heat exchange rate at the top of the burner surface plays a critical role in driving the growth of the perturbations over a wide range of conditions, including resonance. The flame response to the perturbations at its base takes the form of consumption speed oscillations in this region. Flame stand-off distance increases/decreases when the flame-wall interaction strengthens/weakens, impacting the overall dynamics of the heat release. The convective lag between the perturbations and the flame base response govern the phase of heat release rate oscillations. There is an additional convective lag between the perturbations at the flame base and the flame tip which has a weaker impact on the heat release rate oscillations. At higher frequencies, the flame-wall interaction is weaker and the heat release oscillations are driven by the flame area oscillations. The response of the flame to higher amplitude oscillations are used to gain further insight into the mechanisms. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

  14. Numerical Study on Laminar Burning Velocity and Flame Stability of Premixed Methane/Ethylene/Air Flames

    Institute of Scientific and Technical Information of China (English)

    陈珊珊; 蒋勇; 邱榕; 安江涛

    2012-01-01

    A numerical study on premixed methane/ethylene/air flames with various ethylene fractions and equivalence ratios was conducted at room temperature and atmospheric pressure. The effects of ethylene addition on laminar burning velocity, flame structure and flame stability under the condition of lean burning were investigated. The results show that the laminar burning velocity increases with ethylene fraction, especially at a large equivalence ratio. More ethylene addition gives rise to higher concentrations of H, O and OH radicals in the flame, which significantly promotes chemical reactions, and a linear correlation exists between the laminar burning velocity and the maximum H + OH concentration in the reaction zone. With the increase of ethylene fraction, the adiabatic flame temperature is raised, while the inner layer temperature becomes lower, contributing to the enhancement of combustion. Markstein length and Markstein number, representative of the flame stability, increase as more ethylene is added, indicating the tendency of flame stability to improve with ethylene addition.

  15. On the transition from a highly turbulent curved flame into a tulip flame

    Energy Technology Data Exchange (ETDEWEB)

    Kratzel, T.; Pantow, E.; Fischer, M. [German Aerospace Research Establishment, Stuttgart (Germany). Institute of Technical Thermodynamics

    1998-12-31

    Experimental and numerical investigations of premixed flame propagation behaviour associated with vortex interactions due to planar pressure waves crossing a curved flame front have been carried out. The resulting ``tulip flame`` formation in such a closed tube has been studied by Schlieren visualization. The ``tulip flame`` phenomenon was observed only closed tubes, while cellular flame fronts appeared in half-open tubes. A physical model has been developed and implemented in a discrete vortex method combined with a flame tracking algorithm. The numerical method has been applied to model and understand the processes that cause the flame to change from a curved to a tulip shape. The results of the simulation are in good agreement with the experimental observations. (author)

  16. Monitoring Atmospheric Transmission with FLAME

    Science.gov (United States)

    Zimmer, Peter C.; McGraw, J. T.; Zirzow, D. C.; Koppa, M.; Buttler-Pena, K.

    2014-01-01

    Calibration of ground-based observations in the optical and near-infrared requires precise and accurate understanding of atmospheric transmission, at least as precise and accurate as that required for the spectral energy distributions of science targets. Traditionally this has used the Langley extrapolation method, observing targets and calibrators over a range of airmass and extrapolating to zero airmass by assuming a plane-parallel homogeneous atmosphere. The technique we present uses direct measurements of the atmosphere to derive the transmission along the line of sight to science targets at a few well-chosen wavelengths. The Facility Lidar Atmospheric Monitor of Extinction (FLAME) is a 0.5m diameter three Nd:YAG wavelength (355nm, 532nm & 1064nm) elastic backscatter lidar system. Laser pulses are transmitted into the atmosphere in the direction of the science target. Photons scattered back toward the receiver by molecules, aerosols and clouds are collected and time-gated so that the backscatter intensity is measured as a function of range to the scattering volume. The system is housed in a mobile calibration lab, which also contains auxiliary instrumentation to provide a NIST traceable calibration of the transmitted laser power and receiver efficiency. FLAME was designed to create a million photons per minute signal from the middle stratosphere, where the atmosphere is relatively calm and dominated by molecules of the well-mixed atmosphere (O2 & N2). Routine radiosonde measurements of the density at these altitudes constrain the scattering efficiency in this region and, combined with calibration of the transmitter and receiver, the only remaining unknown quantity is the two-way transmission to the stratosphere. These measurements can inform atmospheric transmission models to better understand the complex and ever-changing observatory radiative transfer environment. FLAME is currently under active development and we present some of our ongoing measurements.

  17. Physical and Chemical Processing in Flames

    Science.gov (United States)

    2013-08-12

    than the classical Troe formula, and the development of a Chemical Explosive Mode Analysis ( CEMA ) computation algorithm that allows on-the-fly...6-311++G(d,p) method. 3. Flame Stabilization and Chemical Explosive Mode Analysis ( CEMA ) Flame stabilization is essential in the understanding of

  18. Development of PIV for Microgravity Diffusion Flames

    Science.gov (United States)

    Greenberg, Paul S.; Wernet, Mark P.; Yanis, William; Urban, David L.; Sunderland, Peter B.

    2003-01-01

    Results are presented from the application of Particle Image Velocimetry(PIV) to the overfire region of a laminar gas jet diffusion flame in normal gravity. A methane flame burning in air at 0.98 bar was considered. The apparatus demonstrated here is packaged in a drop rig designed for use in the 2.2 second drop tower.

  19. Chemical processes in the HNF flame

    NARCIS (Netherlands)

    Ermolin, N.E.; Zarko, V.E.; Keizers, H.L.J.

    2006-01-01

    Results of modeling the HNF flame structure are presented. From an analysis of literature data on the thermal decomposition and combustion of HNF, it is concluded that the dissociative vaporization of HNF proceeds via the route HNFliq → (N2H4)g + (HC(NO 2)3)g. The flame structure is modeled using a

  20. Flaming in CMC: Prometheus' Fire or Inferno's?

    Science.gov (United States)

    Abrams, Zsuzsanna Ittzes

    2003-01-01

    Reports on a descriptive study with 75 intermediate college learners of German participating in two sessions of synchronous computer mediated communication during the course of a semester that investigated students' flaming behavior--aggressive interpersonal language and rude behavior. Shows that not only is flaming a very infrequent occurrence,…

  1. Flame retardant cotton barrier nonwovens for mattresses

    Science.gov (United States)

    According to regulation CPSC 16 CFR 1633, every new residential mattress sold in the United States since July 2007 must resist ignition by open flame. An environmentally benign “green”, inexpensive way to meet this regulation is to use a low-cost flame retardant (FR) barrier fabric. In this study, a...

  2. Flame retardant cotton based highloft nonwovens

    Science.gov (United States)

    Flame retardancy has been a serious bottleneck to develop cotton blended very high specific volume bulky High loft fabrics. Alternately, newer approach to produce flame retardant cotton blended High loft fabrics must be employed that retain soft feel characteristics desirable of furnishings. Hence, ...

  3. Flaming in CMC: Prometheus' Fire or Inferno's?

    Science.gov (United States)

    Abrams, Zsuzsanna Ittzes

    2003-01-01

    Reports on a descriptive study with 75 intermediate college learners of German participating in two sessions of synchronous computer mediated communication during the course of a semester that investigated students' flaming behavior--aggressive interpersonal language and rude behavior. Shows that not only is flaming a very infrequent occurrence,…

  4. Physical and Chemical Processes in Turbulent Flames

    Science.gov (United States)

    2015-06-23

    DISTRIBUTION A: Distribution approved for public release. AF Office Of Scientific Research (AFOSR)/ RTE Arlington, Virginia 22203 Air Force Research...two-year subject program, conducted through tight coupling between experiment, theory and computation, and reported in high impact journal articles ...The thrust for this program constitutes of three major areas of turbulent combustion: (1) Flame surface statistics , (2) Flame-turbulence interaction

  5. Simulations of flame generated particles

    KAUST Repository

    Patterson, Robert

    2016-01-05

    The nonlinear structure of the equations describing the evolution of a population of coagulating particles in a flame make the use of stochastic particle methods attractive for numerical purposes. I will present an analysis of the stochastic fluctuations inherent in these numerical methods leading to an efficient sampling technique for steady-state problems. I will also give some examples where stochastic particle methods have been used to explore the effect of uncertain parameters in soot formation models. In conclusion I will try to indicate some of the issues in optimising these methods for the study of uncertain model parameters.

  6. Properties and Mechanism of the Mechanosensitive Ion Channel Inhibitor GsMTx4, a Therapeutic Peptide Derived from Tarantula Venom.

    Science.gov (United States)

    Gottlieb, Philip A; Suchyna, Thomas M; Sachs, Frederick

    2007-01-01

    Mechanosensitive ion channels (MSCs) are found in all types of cells ranging from Escherichia coli to morning glories to humans. They seem to fall into two families: those in specialized receptors, such as the hair cells of the cochlea, and those in cells not clearly differentiated for sensory duty. The physiological function of the channels in nonspecialized cells has not been demonstrated, although their activity has been demonstrated innumerable times in vitro. The only specific reagent to block MSCs isGsMTx4, a 4-kDa peptide isolated from tarantula venom. Despite being isolated from venom, it is nontoxic to mice. GsMTx4 is specific for an MSC subtype, the nonselective cation channels that may be members of the transient receptor potential (TRP) family. GsMTx4 acts as a gating modifier, increasing the energy of the open state relative to the closed state. The mirror image D enantiomer of GsMTx4 is equally active, so mode of action is not via the traditional lock and key model. GsMTx4 probably acts in the boundary lipid of the channel by changing local curvature and mechanically stressing the channel toward the closed state. Despite the lack of definitive physiological data on the function of the cationic MSCs, GsMTx4 may prove useful as a drug or lead compound that can affect physiological processes. These processes would be those driven by mechanical stress, such as blood vessel autoregulation, stress-induced contraction of smooth muscle, and Ca(2+) loading in muscular dystrophy. © 2007, Elsevier Inc. All right reserved.

  7. A Revision of the Selenocosmiine Tarantula Genus Phlogiellus Pocock 1897 (Araneae: Theraphosidae, with Description of 4 New Species

    Directory of Open Access Journals (Sweden)

    Steven C. Nunn

    2016-01-01

    Full Text Available The tarantula genus Phlogiellus (Pocock 1897 is revised. The genus is diagnosed against all other selenocosmiine genera for the first time along with a new generic description. The tribe Yamiini (Kishida 1920 is diagnosed against all other selenocosmiine tribes. All Phlogiellus species are diagnosed from all congeners; all species are mapped. Complete dichotomous keys for both sexes of all species are included. Where appropriate, intraspecific variation is discussed. Four new species are described: P. bogadeki sp. nov. from Hong Kong, P. johnreylazoi sp. nov. from Palawan Island, Philippines, P. moniqueverdezae sp. nov. from Ranong, Thailand, and P. pelidnus sp. nov. from Sabah, Borneo. The type species P. atriceps (Pocock 1897 holotype male is redescribed and the male P. baeri (Simon 1877 is described in detail for the first time. The validity of P. inermis (Ausserer 1871 is confirmed. Relationships between all known selenocosmiine genera and Phlogiellus from the Philippines are discussed and several character traits are newly diagnosed. The tribe Phlogiellini (West et al. 2012 is a junior synonym of Yamiini (Kishida 1920. Selenocosmia orophila (Thorell 1897 from Myanmar, Selenocosmia insulana (Hirst 1909 from Djampea (= Jampea Island, and Selenocosmia obscura (Hirst 1909 from Sarawak, Borneo, are transferred to Phlogiellus, altering the specific names to Phlogiellus orophilus (Thorell 1897 comb. nov., Phlogiellus insulanus (Hirst 1909 comb. nov., and Phlogiellus obscurus (Hirst 1909 comb. nov. Phlogiellus subarmatus (Thorell 1891 is transferred to Chilobrachys (Karsch 1891, becoming Chilobrachys subarmatus (Thorell 1891 comb. nov. Phlogiellus kwebaburdeos (Barrion-Dupo et al., 2014 is transferred to Orphnaecus (Simon 1892, becoming Orphnaecus kwebaburdeos (Barrion-Dupo et al., 2014 comb. nov. Phlogiellus ornatus (Thorell 1897 and Phlogiellus nebulosus (Rainbow 1899 are considered species inquirenda. Phlogiellus baeri (Simon 1877 is no longer

  8. SVM-based prediction of propeptide cleavage sites in spider toxins identifies toxin innovation in an Australian tarantula.

    Directory of Open Access Journals (Sweden)

    Emily S W Wong

    Full Text Available Spider neurotoxins are commonly used as pharmacological tools and are a popular source of novel compounds with therapeutic and agrochemical potential. Since venom peptides are inherently toxic, the host spider must employ strategies to avoid adverse effects prior to venom use. It is partly for this reason that most spider toxins encode a protective proregion that upon enzymatic cleavage is excised from the mature peptide. In order to identify the mature toxin sequence directly from toxin transcripts, without resorting to protein sequencing, the propeptide cleavage site in the toxin precursor must be predicted bioinformatically. We evaluated different machine learning strategies (support vector machines, hidden Markov model and decision tree and developed an algorithm (SpiderP for prediction of propeptide cleavage sites in spider toxins. Our strategy uses a support vector machine (SVM framework that combines both local and global sequence information. Our method is superior or comparable to current tools for prediction of propeptide sequences in spider toxins. Evaluation of the SVM method on an independent test set of known toxin sequences yielded 96% sensitivity and 100% specificity. Furthermore, we sequenced five novel peptides (not used to train the final predictor from the venom of the Australian tarantula Selenotypus plumipes to test the accuracy of the predictor and found 80% sensitivity and 99.6% 8-mer specificity. Finally, we used the predictor together with homology information to predict and characterize seven groups of novel toxins from the deeply sequenced venom gland transcriptome of S. plumipes, which revealed structural complexity and innovations in the evolution of the toxins. The precursor prediction tool (SpiderP is freely available on ArachnoServer (http://www.arachnoserver.org/spiderP.html, a web portal to a comprehensive relational database of spider toxins. All training data, test data, and scripts used are available from

  9. Edge Diffusion Flame Propagation and Stabilization Studied

    Science.gov (United States)

    Takahashi, Fumiaki; Katta, Viswanath R.

    2004-01-01

    In most practical combustion systems or fires, fuel and air are initially unmixed, thus forming diffusion flames. As a result of flame-surface interactions, the diffusion flame often forms an edge, which may attach to burner walls, spread over condensed fuel surfaces, jump to another location through the fuel-air mixture formed, or extinguish by destabilization (blowoff). Flame holding in combustors is necessary to achieve design performance and safe operation of the system. Fires aboard spacecraft behave differently from those on Earth because of the absence of buoyancy in microgravity. This ongoing in-house flame-stability research at the NASA Glenn Research Center is important in spacecraft fire safety and Earth-bound combustion systems.

  10. Interaction Between Flames and Electric Fields Studied

    Science.gov (United States)

    Yuan, Zeng-Guang; Hegde, Uday

    2003-01-01

    The interaction between flames and electric fields has long been an interesting research subject that has theoretical importance as well as practical significance. Many of the reactions in a flame follow an ionic pathway: that is, positive and negative ions are formed during the intermediate steps of the reaction. When an external electric field is applied, the ions move according to the electric force (the Coulomb force) exerted on them. The motion of the ions modifies the chemistry because the reacting species are altered, it changes the velocity field of the flame, and it alters the electric field distribution. As a result, the flame will change its shape and location to meet all thermal, chemical, and electrical constraints. In normal gravity, the strong buoyant effect often makes the flame multidimensional and, thus, hinders the detailed study of the problem.

  11. pVLT-EGFP载体构建及其在巴西固氮螺菌(Azospirillum brasilense)的表达研究%Construction of an Expression Vector pVLT-EGFP and Its Expression in Azospirillum brasilense

    Institute of Scientific and Technical Information of China (English)

    巩涛; 王继雯; 杨文玲; 甄静; 刘莹莹; 李冠杰; 刘莉; 岳丹丹; 陈国参

    2015-01-01

    为了研究巴西固氮螺菌(Azospirillum brasilense)在植物体内的定殖,利用酶切连接的方法,以增强型绿色荧光蛋白(enhanced green fluorescent protein,EGFP)基因与表达栽体pVLT-33为基本元件,构建了重组表达载体pVLT-EGFP,电转巴西固氮螺菌R7细胞,并利用实时荧光定量PCR(qPCR)研究了不同温度、不同时间EGFP mRNA的表达情况.酶切及测序结果表明,成功构建了pVLT-EGFP载体,并在荧光显微镜下观察到绿色荧光蛋白表达;qPCR结果显示:30℃,诱导9hEGFP基因的表达水平最高.本研究成功构建了重组表达载体pVLT-EGFP,为实现pVLT-EGFP的可控表达及研究固氮菌在植物体内的定殖规律及促生长机理提供了一种有效的途径.

  12. Cool Sooting Flames of Hydrocarbons

    Institute of Scientific and Technical Information of China (English)

    Z.A. MANSUROV

    2001-01-01

    This paper presents the study of polycyclic aromatic hydrocarbons (PAH) and paramagnetism of soot particles sampled from cool sooting flames of methane and propane in a separately-heated two-sectional reactor under atmospheric pressure at the reactor temperatures of 670-1170 K. The temperature profiles of the flames were studied. The sampling was carried out with a quartz sampler and the samples were frozen with liquid nitrogen. A number of polyaromatic hydrocarbons such as pyrene, fluoranthene, coronene, anthanthrene, 1,12-benzperylene,were identified by spectroscopic methods in the extract of soot. The processes of soot formation at methaneoxygen mixture combustion in the electric field with applied potential changed from 0 to 2,2 kV at different polarity of electrodes have been investigated. It has been stated that at the electrical field application, an increase in soot particle sizes and soot yield occurs; besides, at the application of the field, speeding up the positively charged particles, the interplanar distance decreases. On the basis of investigation of soot particles paramagnetism, it was shown that initially soot particles have high carcinogetic activity and pollute the environment owing to a rapid decrease of the number of these radical centers. The reduction of the radical concentration is connected with radical recombination on soot.

  13. Experiment and Simulation of Autoignition in Jet Flames and its Relevance to Flame Stabilization and Structure

    KAUST Repository

    Al-Noman, Saeed M.

    2016-06-01

    Autoignition characteristics of pre-vaporized iso-octane, primary reference fuels, gasolines, and dimethyl ether (DME) have been investigated experimentally in a coflow with elevated temperature of air. With the coflow air at relatively low initial temperatures below autoignition temperature Tauto, an external ignition source was required to stabilize the flame. Non-autoignited lifted flames had tribrachial edge structures and their liftoff heights correlated well with the jet velocity scaled by the stoichiometric laminar burning velocity, indicating the importance of the edge propagation speed on flame stabilization balanced with local flow velocity. At high initial temperatures over Tauto, the autoignited flames were stabilized without requiring an external ignition source. The autoignited lifted flames exhibited either tribrachial edge structures or Mild combustion behaviors depending on the level of fuel dilution. For the iso-octane and n-heptane fuels, two distinct transition behaviors were observed in the autoignition regime from a nozzle-attached flame to a lifted tribrachial-edge flame and then a sudden transition to lifted Mild combustion as the jet velocity increased at a certain fuel dilution level. The liftoff data of the autoignited flames with tribrachial edges were analyzed based on calculated ignition delay times for the pre-vaporized fuels. Analysis of the experimental data suggested that ignition delay time may be much less sensitive to initial temperature under atmospheric pressure conditions as compared with predictions. For the gasoline fuels for advanced combustion engines (FACEs), and primary reference fuels (PRFs), autoignited liftoff data were correlated with Research Octane Number and Cetane Number. For the DME fuel, planar laser-induced fluorescence (PLIF) of formaldehyde (CH2O) and CH* chemiluminescence were visualized qualitatively. In the autoignition regime for both tribrachial structure and mild combustion, formaldehyde were found

  14. Flame Structure and Emissions of Strongly-Pulsed Turbulent Diffusion Flames with Swirl

    Science.gov (United States)

    Liao, Ying-Hao

    This work studies the turbulent flame structure, the reaction-zone structure and the exhaust emissions of strongly-pulsed, non-premixed flames with co-flow swirl. The fuel injection is controlled by strongly-pulsing the fuel flow by a fast-response solenoid valve such that the fuel flow is completely shut off between pulses. This control strategy allows the fuel injection to be controlled over a wide range of operating conditions, allowing the flame structure to range from isolated fully-modulated puffs to interacting puffs to steady flames. The swirl level is controlled by varying the ratio of the volumetric flow rate of the tangential air to that of the axial air. For strongly-pulsed flames, both with and without swirl, the flame geometry is strongly impacted by the injection time. Flames appear to exhibit compact, puff-like structures for short injection times, while elongated flames, similar in behaviors to steady flames, occur for long injection times. The flames with swirl are found to be shorter for the same fuel injection conditions. The separation/interaction level between flame puffs in these flames is essentially governed by the jet-off time. The separation between flame puffs decreases as swirl is imposed, consistent with the decrease in flame puff celerity due to swirl. The decreased flame length and flame puff celerity are consistent with an increased rate of air entrainment due to swirl. The highest levels of CO emissions are generally found for compact, isolated flame puffs, consistent with the rapid quenching due to rapid dilution with excess air. The imposition of swirl generally results in a decrease in CO levels, suggesting more rapid and complete fuel/air mixing by imposing swirl in the co-flow stream. The levels of NO emissions for most cases are generally below the steady-flame value. The NO levels become comparable to the steady-flame value for sufficiently short jet-off time. The swirled co-flow air can, in some cases, increase the NO

  15. Scaling of turbulent flame speed for expanding flames with Markstein diffusion considerations.

    Science.gov (United States)

    Chaudhuri, Swetaprovo; Wu, Fujia; Law, Chung K

    2013-09-01

    In this paper we clarify the role of Markstein diffusivity, which is the product of the planar laminar flame speed and the Markstein length, on the turbulent flame speed and its scaling, based on experimental measurements on constant-pressure expanding turbulent flames. Turbulent flame propagation data are presented for premixed flames of mixtures of hydrogen, methane, ethylene, n-butane, and dimethyl ether with air, in near-isotropic turbulence in a dual-chamber, fan-stirred vessel. For each individual fuel-air mixture presented in this work and the recently published iso-octane data from Leeds, normalized turbulent flame speed data of individual fuel-air mixtures approximately follow a Re_{T,f}^{0.5} scaling, for which the average radius is the length scale and thermal diffusivity is the transport property of the turbulence Reynolds number. At a given Re_{T,f}^{}, it is experimentally observed that the normalized turbulent flame speed decreases with increasing Markstein number, which could be explained by considering Markstein diffusivity as the leading dissipation mechanism for the large wave number flame surface fluctuations. Consequently, by replacing thermal diffusivity with the Markstein diffusivity in the turbulence Reynolds number definition above, it is found that normalized turbulent flame speeds could be scaled by Re_{T,M}^{0.5} irrespective of the fuel, equivalence ratio, pressure, and turbulence intensity for positive Markstein number flames.

  16. VLT FORS2 comparative transmission spectral survey of clear and cloudy exoplanet atmospheres

    Science.gov (United States)

    Nikolov, Nikolay; Sing, David; Gibson, Neale; Evans, Thomas; Barstow, Joanna Katy; Kataria, Tiffany; Wilson, Paul A.

    2016-10-01

    Transmission spectroscopy is a key to unlocking the secrets of close-in exoplanet atmospheres. Observations have started to unveil a vast diversity of irradiated giant planet atmospheres with clouds and hazes playing a definitive role across the entire mass and temperature regime. We have initiated a ground-based, multi-object transmission spectroscopy of a hand full of hot Jupiters, covering the wavelength range 360-850nm using the recently upgraded FOcal Reducer and Spectrograph (FORS2) mounted on the Very Large Telescope (VLT) at the European Southern Observatory (ESO). These targets were selected for comparative follow-up as their transmission spectra showed evidence for alkali metal absorption, based on the results of Hubble Space Telescope (HST) observations. This talk will discuss the first results from the programme, demonstrating excellent agreement between the transmission spectra measured from VLT and HST and further reinforce the findings of clear, cloudy and hazy atmospheres. More details will be discussed on the narrow alkali features obtained with FORS2 at higher resolution, revealing its high potential in securing optical transmission spectra. These FORS2 observations are the first ground-based detections of clear, cloudy and hazy hot-Jupiter atmosphere with a simultaneous detections of Na, K, and H2 Rayleigh scattering. Our program demonstrates the large potential of the instrument for optical transmission spectroscopy, capable of obtaining HST-quality light curves from the ground. Compared to HST, the larger aperture of VLT will allow for fainter targets to be observed and higher spectral resolution, which can greatly aid comparative exoplanet studies. This is important for further exploring the diversity of exoplanet atmospheres and is particularly complementary to the near- and mid-IR regime, to be covered by the upcoming James-Webb Space Telescope (JWST) and is readily applicable to less massive planets down to super-Earths.

  17. MOONS: A New Powerful Multi-Object Spectrograph for the VLT

    Science.gov (United States)

    Cirasuolo, M.; MOONS Consortium

    2016-10-01

    MOONS (the Multi-Object Optical and Near-infrared Spectrograph) is a third-generation instrument for the ESO Very Large Telescope (VLT). The large collecting area offered by the VLT (8.2 m diameter), combined with the large multiplex and wavelength coverage (optical to near-IR: 0.64 μm - 1.8 μm) of MOONS will provide the European astronomical community with a powerful, unique instrument able to pioneer a wide range of Galactic, Extragalactic and Cosmological studies, and the crucial follow-up for major facilities such as Gaia, VISTA, Euclid and LSST. MOONS has the observational power needed to unveil galaxy formation and evolution over the entire history of the Universe, from stars in our Milky Way, through the redshift desert, and up to the epoch of the very first galaxies and reionization of the Universe at redshifts of z > 8-9, just a few million years after the Big Bang. From five years of observations MOONS will provide high-quality spectra for >3 M stars in our Galaxy and the Local Group, and for 1-2 M galaxies at z >1 (for an SDSS-like survey), promising to revolutionize our understanding of the Universe. The baseline design consists of 1024 fibers, deployable over a field-of-view of ˜500 sq. arcmin, the largest patrol field offered by the Nasmyth focus at the VLT. The total wavelength coverage is 0.64 μm - 1.8 μm with two spectral resolving power settings: in the medium-resolution mode (R˜4,000-6,000) the entire wavelength range is observed simultaneously, while the high-resolution mode will cover simultaneously selected sub-regions: one region with R˜9,000 near the Ca II triplet to measure stellar radial velocities, and part of the H-band at R˜20,000 for precision measurements of chemical abundances.

  18. PC based PLCs and ethernet based fieldbus: the new standard platform for future VLT instrument control

    Science.gov (United States)

    Kiekebusch, Mario J.; Lucuix, Christian; Erm, Toomas M.; Chiozzi, Gianluca; Zamparelli, Michele; Kern, Lothar; Brast, Roland; Pirani, Werther; Reiss, Roland; Popovic, Dan; Knudstrup, Jens; Duchateau, Michel; Sandrock, Stefan; Di Lieto, Nicola

    2014-07-01

    ESO is currently in the final phase of the standardization process for PC-based Programmable Logical Controllers (PLCs) as the new platform for the development of control systems for future VLT/VLTI instruments. The standard solution used until now consists of a Local Control Unit (LCU), a VME-based system having a CPU and commercial and proprietary boards. This system includes several layers of software and many thousands of lines of code developed and maintained in house. LCUs have been used for several years as the interface to control instrument functions but now are being replaced by commercial off-the-shelf (COTS) systems based on BECKHOFF Embedded PCs and the EtherCAT fieldbus. ESO is working on the completion of the software framework that enables a seamless integration into the VLT control system in order to be ready to support upcoming instruments like ESPRESSO and ERIS, that will be the first fully VLT compliant instruments using the new standard. The technology evaluation and standardization process has been a long and combined effort of various engineering disciplines like electronics, control and software, working together to define a solution that meets the requirements and minimizes the impact on the observatory operations and maintenance. This paper presents the challenges of the standardization process and the steps involved in such a change. It provides a technical overview of how industrial standards like EtherCAT, OPC-UA, PLCOpen MC and TwinCAT can be used to replace LCU features in various areas like software engineering and programming languages, motion control, time synchronization and astronomical tracking.

  19. Laminar Soot Processes Experiment Shedding Light on Flame Radiation

    Science.gov (United States)

    Urban, David L.

    1998-01-01

    The Laminar Soot Processes (LSP) experiment investigated soot processes in nonturbulent, round gas jet diffusion flames in still air. The soot processes within these flames are relevant to practical combustion in aircraft propulsion systems, diesel engines, and furnaces. However, for the LSP experiment, the flames were slowed and spread out to allow measurements that are not tractable for practical, Earth-bound flames.

  20. Flaming: More than a Necessary Evil for Academic Mailing Lists?

    Science.gov (United States)

    Wang, Hongjie

    1996-01-01

    States that although Internet "gurus" advocate that users refrain from "flaming," in fact, flaming permeates the Internet. Explores the nature of flaming in its characteristics and forms as seen in academic discussion groups. Argues that flaming educates the ignorant, tames the uncouth, and promotes effective communication. (PA)

  1. VLT transit and occultation photometry for the bloated planet CoRoT-1b

    OpenAIRE

    Gillon, Michaël; Demory, B. -O.; Triaud, A. H. M. J.; Barman, T; Hebb, L.; Montalban Iglesias, Josefa; Maxted, P.; Queloz, D; Deleuil, M.; Magain, Pierre

    2009-01-01

    We present VLT eclipse photometry for the giant planet CoRoT-1b. We observed a transit in the R-band filter and an occultation in a narrow filter centered on 2.09 microns. Our analysis of this new photometry and published radial velocities, in combination with stellar-evolutionary modeling, leads to a planetary mass and radius of 1.07 (+0.13,-0.18) M_Jup and 1.45 (+0.07,-0.13) R_Jup, confirming the very low density previously deduced from CoRoT photometry. The large occultation depth that we ...

  2. Trends and developments in VLT data papers as seen through telbib

    Science.gov (United States)

    Bordelon, Dominic; Grothkopf, Uta; Meakins, Silvia; Sterzik, Michael

    2016-07-01

    The ESO Telescope Bibliography (telbib; http://telbib.eso.org) is a database of refereed papers published by the ESO users community. It links data in the ESO Science Archive with the published literature, and vice versa. Developed and maintained by the ESO library, telbib also provides insights into the organization's research output and impact as measured through bibliometric studies. Numerous reports, statistics, and visualizatons derived from telbib help to understand the way in which the user community uses ESO/VLT data in publications. Based on selected use cases, we will showcase recent trends and developments.

  3. The dilution effect on the extinction of wall diffusion flame

    Directory of Open Access Journals (Sweden)

    Ghiti Nadjib

    2014-12-01

    Full Text Available The dynamic process of the interaction between a turbulent jet diffusion methane flame and a lateral wall was experimentally studied. The evolution of the flame temperature field with the Nitrogen dilution of the methane jet flame was examined. The interaction between the diffusion flame and the lateral wall was investigated for different distance between the wall and the central axes of the jet flame. The dilution is found to play the central role in the flame extinction process. The flame response as the lateral wall approaches from infinity and the increasing of the dilution rate make the flame extinction more rapid than the flame without dilution, when the nitrogen dilution rate increase the flame temperature decrease.

  4. Structure of a poly(ethylene) opposed flow diffusion flame

    Energy Technology Data Exchange (ETDEWEB)

    Pitz, W.J.; Brown, N.J.; Sawyer, R.F.

    1980-08-01

    Structural measurements were obtained and compared with other investigations of diffusion flames. Departures from the commonly assumed collapsed flame model of laminar diffusion flames were observed in terms of excessive CO concentrations and oxygen penetration into the fuel side of the flame. An upper bound on the importance of oxygen diffusion to the fuel surface and subsequent surface oxidation was placed at 20% of the energy required for fuel pyrolysis, with the remainder of the energy being delivered to the surface from the flame through heat transfer processes. As the oxygen concentration in the oxidizer flow was decreased and extinction conditions approached, the CO/CO/sub 2/ ratio at the flame increased slightly, the oxygen concentration at the luminous flame zone decreased, the flame stand-off distance decreased, and the flame temperature decreased. Radial similarity in the composition and temperature profiles was established experimentally which confirms predictions and greatly simplifies the modeling of the opposed flow diffusion flame.

  5. Aromatics oxidation and soot formation in flames

    Energy Technology Data Exchange (ETDEWEB)

    Howard, J.B.; Pope, C.J.; Shandross, R.A.; Yadav, T. [Massachusetts Institute of Technology, Cambridge (United States)

    1993-12-01

    This project is concerned with the kinetics and mechanisms of aromatics oxidation and soot and fullerenes formation in flames. The scope includes detailed measurements of profiles of stable and radical species concentrations in low-pressure one-dimensional premixed flames. Intermediate species identifications and mole fractions, fluxes, and net reaction rates calculated from the measured profiles are used to test postulated reaction mechanisms. Particular objectives are to identify and to determine or confirm rate constants for the main benzene oxidation reactions in flames, and to characterize fullerenes and their formation mechanisms and kinetics.

  6. Systems and methods for controlling flame instability

    KAUST Repository

    Cha, Min Suk

    2016-07-21

    A system (62) for controlling flame instability comprising: a nozzle (66) coupled to a fuel supply line (70), an insulation housing (74) coupled to the nozzle, a combustor (78) coupled to the nozzle via the insulation housing, where the combustor is grounded (80), a pressure sensor (82) coupled to the combustor and configured to detect pressure in the combustor, and an instability controlling assembly coupled to the pressure sensor and to an alternating current power supply (86), where, the instability controlling assembly can control flame instability of a flame in the system based on pressure detected by the pressure sensor.

  7. Novel Flame-Based Synthesis of Nanowires for Multifunctional Application

    Science.gov (United States)

    2015-05-13

    laser-based diagnostics for in-situ Raman characterization of as- synthesized nanomaterials, (iv) flame synthesis of graphene , (v) flame synthesis of...laser- based diagnostics for in-situ Raman characterization of as-synthesized nanomaterials, (iv) flame synthesis of graphene , (v) flame synthesis of...Stephen D. Tse, Manish Chhowalla, Bernard H. Kear. Role of substrate, temperature, and hydrogen on the flame synthesis of graphene films, Proceedings

  8. Acoustically Forced Coaxial Hydrogen / Liquid Oxygen Jet Flames

    Science.gov (United States)

    2016-05-15

    visualized for both reacting and nonreacting cases. The jet flame was studied unforced, without acoustics , and forced, with transverse acoustic waves in...liquid rocket injector flames react to acoustic waves . In this study, a representative coaxial gaseous hydrogen / liquid oxygen (LOX) jet flame is...hydrogen / liquid oxygen (LOX) jet flame is visualized for both reacting and nonreacting cases. The jet flame was studied unforced, without acoustics , and

  9. Sm-Nd and Rb-Sr Isotopic Studies of Meteorite Kalahari 009: An Old VLT Mare Basalt

    Science.gov (United States)

    Shih, C.-Y.; Nyquist, L. E.; Reese, Y.; Bischoff, A.

    2008-01-01

    Lunar meteorite Kalahari 009 is a fragmental basaltic breccia contain ing various very-low-Ti (VLT) mare basalt clasts embedded in a fine-g rained matrix of similar composition. This meteorite and lunar meteorite Kalahari 008, an anorthositic breccia, were suggested to be paired mainly due to the presence of similar fayalitic olivines in fragment s found in both meteorites. Thus, Kalahari 009 probably represents a VLT basalt that came from a locality near a mare-highland boundary r egion of the Moon, as compared to the typical VLT mare basalt samples collected at Mare Crisium during the Luna-24 mission. The concordant Sm-Nd and Ar-Ar ages of such a VLT basalt (24170) suggest that the extrusion of VLT basalts at Mare Crisium occurred 3.30 +/- 0.05 Ga ag o. Previous age results for Kalahari 009 range from approximately 4.2 Ga by its Lu-Hf isochron age to 1.70?0.04 Ga of its Ar-Ar plateau ag e. However, recent in-situ U-Pb dating of phosphates in Kalahari 009 defined an old crystallization age of 4.35+/- 0.15 Ga. The authors su ggested that Kalahari 009 represents a cryptomaria basalt. In this r eport, we present Sm-Nd and Rb-Sr isotopic results for Kalahari 009, discuss the relationship of its age and isotopic characteristics to t hose of other L-24 VLT mare basalts and other probable cryptomaria ba salts represented by Apollo 14 aluminous mare basalts, and discuss it s petrogenesis.

  10. Heat release and flame structure measurements of self-excited acoustically-driven premixed methane flames

    Energy Technology Data Exchange (ETDEWEB)

    Kopp-Vaughan, Kristin M.; Tuttle, Steven G.; Renfro, Michael W. [Department of Mechanical Engineering, University of Connecticut, 191 Auditorium Rd, U-3139, Storrs, CT 06269 (United States); King, Galen B. [School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907 (United States)

    2009-10-15

    An open-open organ pipe burner (Rijke tube) with a bluff-body ring was used to create a self-excited, acoustically-driven, premixed methane-air conical flame, with equivalence ratios ranging from 0.85 to 1.05. The feed tube velocities corresponded to Re = 1780-4450. Coupled oscillations in pressure, velocity, and heat release from the flame are naturally encouraged at resonant frequencies in the Rijke tube combustor. This coupling creates sustainable self-excited oscillations in flame front area and shape. The period of the oscillations occur at the resonant frequency of the combustion chamber when the flame is placed {proportional_to}1/4 of the distance from the bottom of the tube. In this investigation, the shape of these acoustically-driven flames is measured by employing both OH planar laser-induced fluorescence (PLIF) and chemiluminescence imaging and the images are correlated to simultaneously measured pressure in the combustor. Past research on acoustically perturbed flames has focused on qualitative flame area and heat release relationships under imposed velocity perturbations at imposed frequencies. This study reports quantitative empirical fits with respect to pressure or phase angle in a self-generated pressure oscillation. The OH-PLIF images were single temporal shots and the chemiluminescence images were phase averaged on chip, such that 15 exposures were used to create one image. Thus, both measurements were time resolved during the flame oscillation. Phase-resolved area and heat release variations throughout the pressure oscillation were computed. A relation between flame area and the phase angle before the pressure maximum was derived for all flames in order to quantitatively show that the Rayleigh criterion was satisfied in the combustor. Qualitative trends in oscillating flame area were found with respect to feed tube flow rates. A logarithmic relation was found between the RMS pressure and both the normalized average area and heat release rate

  11. Direct numerical simulations of non-premixed ethylene-air flames: Local flame extinction criterion

    KAUST Repository

    Lecoustre, Vivien R.

    2014-11-01

    Direct Numerical Simulations (DNS) of ethylene/air diffusion flame extinctions in decaying two-dimensional turbulence were performed. A Damköhler-number-based flame extinction criterion as provided by classical large activation energy asymptotic (AEA) theory is assessed for its validity in predicting flame extinction and compared to one based on Chemical Explosive Mode Analysis (CEMA) of the detailed chemistry. The DNS code solves compressible flow conservation equations using high order finite difference and explicit time integration schemes. The ethylene/air chemistry is simulated with a reduced mechanism that is generated based on the directed relation graph (DRG) based methods along with stiffness removal. The numerical configuration is an ethylene fuel strip embedded in ambient air and exposed to a prescribed decaying turbulent flow field. The emphasis of this study is on the several flame extinction events observed in contrived parametric simulations. A modified viscosity and changing pressure (MVCP) scheme was adopted in order to artificially manipulate the probability of flame extinction. Using MVCP, pressure was changed from the baseline case of 1 atm to 0.1 and 10 atm. In the high pressure MVCP case, the simulated flame is extinction-free, whereas in the low pressure MVCP case, the simulated flame features frequent extinction events and is close to global extinction. Results show that, despite its relative simplicity and provided that the global flame activation temperature is correctly calibrated, the AEA-based flame extinction criterion can accurately predict the simulated flame extinction events. It is also found that the AEA-based criterion provides predictions of flame extinction that are consistent with those provided by a CEMA-based criterion. This study supports the validity of a simple Damköhler-number-based criterion to predict flame extinction in engineering-level CFD models. © 2014 The Combustion Institute.

  12. High pressure flame system for pollution studies with results for methane-air diffusion flames

    Science.gov (United States)

    Miller, I. M.; Maahs, H. G.

    1977-01-01

    A high pressure flame system was designed and constructed for studying nitrogen oxide formation in fuel air combustion. Its advantages and limitations were demonstrated by tests with a confined laminar methane air diffusion flame over the pressure range from 1 to 50 atm. The methane issued from a 3.06 mm diameter port concentrically into a stream of air contained within a 20.5 mm diameter chimney. As the combustion pressure is increased, the flame changes in shape from wide and convex to slender and concave, and there is a marked increase in the amount of luminous carbon. The height of the flame changes only moderately with pressure.

  13. CROMOS A cryogenic near-infrared, multi-object spectrometer for the VLT

    CERN Document Server

    Genzel, R; Tomono, D; Thatte, N; Eisenhauer, F; Lehnert, M; Tecza, M; Bender, R

    2001-01-01

    We discuss a cryogenic, multi-object near-infrared spectrometer as a second generation instrument for the VLT. The spectrometer combines 20 to 40 independent integral eld units (IFUs), which can be positioned by a cryogenic robot over the entire unvignetted eld of the VLT (~7'). Each IFU consists of a contiguous cluster of 20 to 30 pixels (0.15 to 0.25" per pixel). The individual IFUs have cold fore-optics and couple into the spectrograph with integrated bers-microlenses. The spectrometer has lambda/d-lambda~4000 and simultaneously covers the J-, H-, and K-bands with three HAWAII 2 detectors. The system is designed for operation both in seeing limited and MCAO modes. Its speed is approximately 3500 times greater than that of ISAAC and 60 times greater than NIRMOS (in H-band). The proposed instrument aims at a wide range of science, ranging from studies of galaxies/clusters in the high-z Universe (dynamics and star formation in z>1 galaxies, evolution of ellipticals, properties of distant, obscured far-IR and ...

  14. High-precision astrometry on the VLT/FORS1 at time scales of few days

    CERN Document Server

    Lazorenko, P F; Dominik, M; Pepe, F; Ségransan, D; Udry, S

    2007-01-01

    We investigate the accuracy of astrometric measurements with the VLT/FORS1 camera and consider potential applications. The study is based on two-epoch (2000 and 2002/2003) frame series of observations of a selected Galactic Bulge sky region that were obtained with FORS1 during four consecutive nights each. Reductions were carried out with a novel technique that eliminates atmospheric image motion and does not require a distinction between targets and reference objects. The positional astrometric precision was found to be limited only by the accuracy of the determination of the star photocentre, which is typically 200-300 microarcsec per single measurement for bright unsaturated stars B=18-19. Several statistical tests have shown that at time-scales of 1-4 nights the residual noise in measured positions is essentially a white noise with no systematic instrumental signature and no significant deviation from a Gaussian distribution. Some evidence of a good astrometric quality of the VLT for frames separated by t...

  15. Final binary star results from the ESO VLT Lunar occultations program

    Energy Technology Data Exchange (ETDEWEB)

    Richichi, A. [National Astronomical Research Institute of Thailand, 191 Siriphanich Bldg., Huay Kaew Road, Suthep, Muang, Chiang Mai 50200 (Thailand); Fors, O. [Departament Astronomia i Meteorologia and Institut de Ciències del Cosmos (ICC), Universitat de Barcelona (UB/IEEC), Martí i Franqués 1, E-08028 Barcelona (Spain); Cusano, F. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Ivanov, V. D., E-mail: andrea4work@gmail.com [European Southern Observatory, Ave. Alonso de Cordova 3107, Casilla 19001, Santiago 19 (Chile)

    2014-03-01

    We report on 13 subarcsecond binaries, detected by means of lunar occultations in the near-infrared at the ESO Very Large Telescope (VLT). They are all first-time detections except for the visual binary HD 158122, which we resolved for the first time in the near-infrared. The primaries have magnitudes in the range K = 4.5-10.0, and companions in the range K = 6.8-11.1. The magnitude differences have a median value of 2.4, with the largest being 4.6. The projected separations are in the range of 4-168 mas, with a median of 13 mas. We discuss and compare our results with the available literature. With this paper, we conclude the mining for binary star detections in the 1226 occultations recorded at the VLT with the ISAAC instrument. We expect that the majority of these binaries may be unresolvable by adaptive optics on current telescopes, and they might be challenging for long-baseline interferometry. However, they constitute an interesting sample for future larger telescopes and for astrometric missions such as GAIA.

  16. VLT/FORS2 observations of the optical counterpart of the isolated neutron star RBS 1774

    CERN Document Server

    Mignani, R P; Turolla, R; Haberl, F; Cropper, M; Motch, C; Treves, A; Zampieri, L

    2011-01-01

    X-ray observations performed with ROSAT led to the discovery of a group (seven to date) of X-ray dim and radio-silent middle-aged isolated neutron stars (a.k.a. XDINSs), which are characterised by pure blackbody spectra (kT~40-100 eV), long X-ray pulsations (P=3-12 s), and appear to be endowed with relatively high magnetic fields, (B~10d13-14 G). RBS 1774 is one of the few XDINSs with a candidate optical counterpart, which we discovered with the VLT. We performed deep observations of RBS 1774 in the R band with the VLT to disentangle a non-thermal power-law spectrum from a Rayleigh-Jeans, whose contributions are expected to be very much different in the red part of the spectrum. We did not detect the RBS 1774 candidate counterpart down to a 3 sigma limiting magnitude of R~27. The constraint on its colour, (B-R)<0.6, rules out that it is a background object, positionally coincident with the X-ray source. Our R-band upper limit is consistent with the extrapolation of the B-band flux (assuming a 3 sigma uncer...

  17. Probing unexplored territories with MUSE: a second generation instrument for the VLT

    CERN Document Server

    Bacon, R; Böhm, P; Boudon, D; Brau-Nogue, S; Caillier, P; Capoani, L; Carollo, C M; Champavert, N; Contini, T; Daguise, E; Dalle, D; Delabre, B; Devriendt, J; Dreizler, S; Du Bois, J; Dupieux, M; Dupin, J P; Emsellem, E; Ferruit, P; Franx, M; Gallou, G; Gerssen, J; Guiderdoni, B; Hahn, T; Hofmann, D; Jarno, A; Kelz, A; Köhler, C; Kollatschny, W; Kosmalski, J; Laurent, F; Lilly, S J; Lizon, J; Loupias, M; Lynn, S; Manescau, A; McDermid, R M; Monstein, C; Nicklas, H; Pares, L; Pasquini, L; Pecontal-Rousset, A; Pécontal, E; Pellò, R; Petit, C; Picat, J P; Popow, E; Quirrenbach, Andreas G; Reiss, R; Renault, E; Roth, M; Schaye, J; Soucail, G; Steinmetz, M; Stroebele, S; Stuik, R; Weilbacher, P; Wozniak, H; De Zeeuw, P T

    2006-01-01

    The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph under preliminary design study. MUSE has a field of 1x1 arcmin**2 sampled at 0.2x0.2 arcsec**2 and is assisted by the VLT ground layer adaptive optics ESO facility using four laser guide stars. The simultaneous spectral range is 465-930 nm, at a resolution of R~3000. MUSE couples the discovery potential of a large imaging device to the measuring capabilities of a high-quality spectrograph, while taking advantage of the increased spatial resolution provided by adaptive optics. This makes MUSE a unique and tremendously powerful instrument for discovering and characterizing objects that lie beyond the reach of even the deepest imaging surveys. MUSE has also a high spatial resolution mode with 7.5x7.5 arcsec**2 field of view sampled at 25 milli-arcsec. In this mode MUSE should be able to obtain diffraction limited data-cubes in the 600-930 nm wavelength range. Although the MUSE design has been optimized f...

  18. Using the VLT to analyze the compact photoionized regions in NGC 3109

    Directory of Open Access Journals (Sweden)

    M. Peña

    2007-01-01

    Full Text Available Veinte nebulosas planetarias (NP y numerosas regiones HII compactas fueron detectadas en la galaxia irregular NGC3109, mediante imágenes \\en-línea" y \\fuera de línea" en [O III] 5007 obtenidas con el ESO VLT. Las NPs fueron seleccionadas como objetos estelares que no mostraran continuo estelar. Espectroscopia obtenida con el VLT FORS1 en modo multi-objeto ha permitido confirmar la naturaleza de NP para varias candidatas. Se ha obtenido también espectroscopia para varias regiones HII compactas. Los espectros son profundos de manera que muchos objetos muestran [O III] 4363 y se puede determinar la temperatura de las regiones, permitiendo analizar la composición química de NPs y regiones HII. Encontramos que las regiones HII muestran una composición química (O/H muy homogénea (en promedio 12 + log O/H = 7.79_0.10, en tanto que las NPs muestran variaciones grandes de composición química y un aparente enriquecimiento en oxígeno.

  19. VLT FORS2 comparative transmission spectral survey of clear and cloudy exoplanet atmospheres

    Science.gov (United States)

    Nikolov, Nikolay; Sing, David K.; Gibson, Neale; Fortney, Jonathan J.; Evans, Tom M.; Barstow, Joanna; Kataria, Tiffany; Wilson, Paul

    2017-01-01

    Thousands of transiting exoplanets are known today but not many have been studied in transmission. While observations with the Hubble Space Telescope (HST) have started to reveal a diversity of atmosphere types, drawing robust conclusions about the underlying population is hampered by the small sample size. This can be greatly aided by ground-based telescopes, equipped with multi-object spectrographs by their unprecedented access to the abundance of fainter systems that HST cannot observe. We have initiated a ground-based, multi-object transmission spectroscopy of a handful of hot gas-giants, covering the wavelength range 360-850nm, using the recently upgraded FOcal Reducer and Spectrograph (FORS2) mounted on the Very Large Telescope (VLT). These exoplanets were selected for a comparative follow-up as their transmission spectra showed evidence for alkali metal absorption, based on the results of HST observations. Here we will discuss first results from the program, demonstrating an excellent agreement between the transmission spectra measured from VLT and HST and detections of Na and K absorption and scattering by clouds/hazes in the atmospheres of several exoplanets. More details will be discussed on the narrow alkali features obtained with FORS2 at higher resolution, revealing its high potential in obtaining optical transmission spectra, which can greatly aid comparative exoplanet studies.

  20. VLT/UVES constraints on the cosmological variability of the fine-structure constant

    CERN Document Server

    Levshakov, S A; Molaro, P; D'Odorico, S

    2004-01-01

    A differential many-multiplet (DMM) technique is developed to probe the variability of alpha. Applied to the FeII lines of the metal absorption line system at zabs = 1.839 in the spectrum of Q1101-264 obtained by means of the UV-Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT), the DMM provides da/a = (4.3+/-7.8) 10^{-6}.The zabs = 1.15 FeII system toward HE0515-4414 has been re-analyzed by the DMM method thus obtaining for the combined sample da/a = (0.7+/-3.1) 10^{-6}. These values are shifted with respect to the Keck/HIRES mean da/a = (-5.7+/-1.1) 10^{-6} (Murphy et al. 2004) at very high confidence level (95%). The fundamental photon noise limitation in the da/a measurement with the VLT/UVES is discussed to figure the prospects for future observations. It is suggested that with a spectrograph of 10 times the UVES resolution coupled to a 100m class telescope the present Oklo level (da/a >= 4.5 10^{-8}) can be achieved along cosmological distances with differential measurements of da...

  1. VLT observations of the asymmetric Etched Hourglass Nebula, MyCn 18

    CERN Document Server

    Clyne, N; Lloyd, M; Matsuura, M; Singh, N; Meaburn, J

    2014-01-01

    Context. The mechanisms that form extreme bipolar planetary nebulae remain unclear. Aims. The physical properties, structure, and dynamics of the bipolar planetary nebula, MyCn 18, are investigated in detail with the aim of understanding the shaping mechanism and evolutionary history of this object. Methods. VLT infrared images, VLT ISAAC infrared spectra, and long-slit optical Echelle spectra are used to investigate MyCn 18. Morpho-kinematic modelling was used to firmly constrain the structure and kinematics of the source. A timescale analysis was used to determine the kinematical age of the nebula and its main components. Results. A spectroscopic study of MyCn 18's central and offset region reveals the detailed make-up of its nebular composition. Molecular hydrogen, atomic helium, and Bracket gamma emission are detected from the central regions of MyCn 18. ISAAC spectra from a slit position along the narrow waist of the nebula demonstrate that the ionised gas resides closer to the centre of the nebula than ...

  2. Theory of DDT in unconfined flames

    CERN Document Server

    Khokhlov, A M; Wheeler, J C; Wheeler, J Craig

    1996-01-01

    This paper outlines a theoretical approach for predicting the onset of detonation in unconfined turbulent flames which is relevant both to problems of terrestrial combustion and to thermonuclear burning in Type Ia supernovae. Two basic assumuptions are made: 1) the gradient mechanism is the inherent mechanism that leads to DDT in unconfined conditions, and 2) the sole mechanism for preparing the gradient in induction time is by turbulent mixing and local flame quenching. The criterion for DDT is derived in terms of the one-dimensional detonation wave thickness, the laminar flame speed, and the laminar flame thickness in the reactive gas. This approach gives a lower-bound criterion for DDT for conditions where shock preheating, wall effects, and interactions with obstacles are absent. Regions in parameter space where unconfined DDT can and cannot occur are determined. A subsequent paper will address these issues specifically in the astrophysical context.

  3. Quantification of non-LTE contributions to OH rotational temperatures based on VLT/X-shooter, VLT/UVES, and TIMED/SABER data

    Science.gov (United States)

    Noll, Stefan; Kausch, Wolfgang; Kimeswenger, Stefan; Proxauf, Bastian; Unterguggenberger, Stefanie; Jones, Amy M.

    2016-04-01

    The hydroxyl (OH) airglow emission is very valuable for estimating atmospheric temperatures at about 87 km because it is relatively easy to measure. The usual approach is based on intensity ratios of OH lines with low rotational upper levels of a given band and the assumption of a Boltzmann distribution of the level populations consistent with the ambient temperature. However, this assumption can be unrealistic if the frequency of thermalising collisions is too low, which is most likely at the highest emission altitudes. We have investigated the amounts of possible non-LTE contributions to the measured OH rotational temperatures depending on the selected lines, band, and time of observation. For this, we used several hundred spectra from the echelle spectrograph X-shooter at the Very Large Telescope (VLT) at Cerro Paranal in Chile. These data with a very wide wavelength coverage allowed us to simultaneously measure temperatures for 25 OH bands and two O2 bands. The latter were used to obtain reference temperatures, which is possible since the radiative lifetimes of the upper states are sufficiently long for establishing full thermalisation for the populations of the different rotational levels. For a comparison of the resulting temperatures, a correction of the different emission altitudes is required. Hence, we also used CO2-based temperature and OH and O2 emission profile data from the SABER multi-channel radiometer on the TIMED satellite. The altitude-corrected OH rotational temperatures show significant non-LTE effects for higher vibrational levels of the upper state v' and especially even v'. The maximum deviations of more than 10 K were found for v' = 8. The non-LTE effects can vary within a range of a few K. The studied nocturnal variations indicate that the non-LTE contributions increase when the emission layer rises. Finally, we will also present first results for several thousand spectra taken with the VLT high-resolution optical echelle spectrograph UVES

  4. Development, validity, and normative data study for the 12-word Philadelphia Verbal Learning Test [czP(r)VLT-12] among older and very old Czech adults.

    Science.gov (United States)

    Bezdicek, Ondrej; Libon, David J; Stepankova, Hana; Panenkova, Erika; Lukavsky, Jiri; Garrett, Kelly Davis; Lamar, Melissa; Price, Catherine C; Kopecek, Miloslav

    2014-01-01

    The aim of the present study was to assess the validity of a 12-word Czech version of the Philadelphia (repeatable) Verbal Learning Test [czP(r)VLT-12]. The construction of the czP(r)VLT-12 was modeled after the California Verbal Learning Test (CVLT) and the nine-word Philadelphia (repeatable) Verbal Learning Test [P(r)VLT]. The czP(r)VLT-12 was constructed from a large corpus of old (60-74) and very old (75-96) Czech adults (n = 540). Participants met strict inclusion criteria for the absence of any active or past neurodegenerative disorders and performed within normal limits on other neuropsychological measures. Principal component analysis (PCA) and correlations between czP(r)VLT-12 factor structure and other memory tests were conducted. The czP(r)VLT-12 produced a four-factor solution, accounting for 70.90% of variance, with factors related to: (1) recall, (2) extra-list intrusion errors/recognition foils, (3) interference, and (4) acquisition rate; a solution similar to the CVLT and P(r)VLT. Increasing age resulted in a decline in most czP(r)VLT-12 indices, women outperformed men, and higher education led to higher scores. Memory performance in normal aging did not correlate with instrumental activities of daily living. Low, but significant, correlations were seen with other tests of cognitive performance (divergent validity). Appendices are available that provide normed percentile estimates of individual czP(r)VLT-12 performance stratified by age, education, and gender. In accordance with previous studies, these results demonstrate the usefulness of czP(r)VLT-12 in assessing declarative memory in older adults.

  5. Flaming Pear Creative Pack1.0

    Institute of Scientific and Technical Information of China (English)

    Kane

    2003-01-01

    Flaming Pear是个一直给我留下深刻印象的软件开发公司。我以前评论过很多这个公司的插件,每一次都是不错的经历。同样的优良传统同样体现在Flaming Pear的新品Creative Pack1.0

  6. NO concentration imaging in turbulent nonpremixed flames

    Energy Technology Data Exchange (ETDEWEB)

    Schefer, R.W. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    The importance of NO as a pollutant species is well known. An understanding of the formation characteristics of NO in turbulent hydrocarbon flames is important to both the desired reduction of pollutant emissions and the validation of proposed models for turbulent reacting flows. Of particular interest is the relationship between NO formation and the local flame zone, in which the fuel is oxidized and primary heat release occurs. Planar imaging of NO provides the multipoint statistics needed to relate NO formation to the both the flame zone and the local turbulence characteristics. Planar imaging of NO has been demonstrated in turbulent flames where NO was seeded into the flow at high concentrations (2000 ppm) to determine the gas temperature distribution. The NO concentrations in these experiments were significantly higher than those expected in typical hydrocarbon-air flames, which require a much lower detectability limit for NO measurements. An imaging technique based on laser-induced fluorescence with sufficient sensitivity to study the NO formation mechanism in the stabilization region of turbulent lifted-jet methane flames.

  7. Synthesis of Nano-Particles in Flames

    DEFF Research Database (Denmark)

    Johannessen, Tue

    The scope of this work is to investigate the synthesis of aluminum oxide particles in flames from the combustion of an aluminum alkoxide precursor.A general introduction to particles formation in the gas phase is presented with emphasis on the mechanisms that control the particle morphology after...... for the analysis of particle formation in flames. Good results for a wide range of operating conditions were obtained. Therefore, the method should be useful as a tool for the optimization and/or design of flame processes for particle production.......The scope of this work is to investigate the synthesis of aluminum oxide particles in flames from the combustion of an aluminum alkoxide precursor.A general introduction to particles formation in the gas phase is presented with emphasis on the mechanisms that control the particle morphology after...... flame burner and a premixed burner with a precursor jet. The experimental setups and results are shown and discussed in detail. Alumina powder with specific surface area between 45 m2/g and 190 m2/g was obtained.Temperature and flow fields of the flame processes are analysed by numerical simulations...

  8. Conical quarl swirl stabilized non-premixed flames: flame and flow field interaction

    KAUST Repository

    Elbaz, Ayman M.

    2017-09-19

    The flame-flow field interaction is studied in non-premixed methane swirl flames stabilized in quartz quarl via simultaneous measurements of the flow field using a stereo PIV and OH-PLIF at 5 KHz repetition rate. Under the same swirl intensity, two flames with different fuel jet velocity were investigated. The time-averaged flow field shows a unique flow pattern at the quarl exit, where two recirculation vortices are formed; a strong recirculation zone formed far from the quarl exit and a larger recirculation zone extending inside the quarl. However, the instantaneous images show that, the flow pattern near the quarl exit plays a vital role in the spatial location and structure of the reaction zone. In the low fuel jet velocity flame, a pair of vortical structures, located precisely at the corners of the quarl exit, cause the flame to roll up into the central region of low speed flow, where the flame sheet then tracks the axial velocity fluctuations. The vorticity field reveals a vortical structure surrounding the reaction zones, which reside on a layer of low compressive strain adjacent to that vortical structure. In the high fuel jet velocity flame, initially a laminar flame sheet resides at the inner shear layer of the main jet, along the interface between incoming fresh gas and high temperature recirculating gas. Further downstream, vortex breakdown alters the flame sheet path toward the central flame region. The lower reaction zones show good correlation to the regions of maximum vorticity and track the regions of low compressive strain associated with the inner shear layer of the jet flow. In both flames the reactions zones conform the passage of the large structure while remaining inside the low speed regions or at the inner shear layer.

  9. Preparation of Flame Retardant Modified with Titanate for Asphalt Binder

    Directory of Open Access Journals (Sweden)

    Bo Li

    2014-01-01

    Full Text Available Improving the compatibility between flame retardant and asphalt is a difficult task due to the complex nature of the materials. This study explores a low dosage compound flame retardant and seeks to improve the compatibility between flame retardants and asphalt. An orthogonal experiment was designed taking magnesium hydroxide, ammonium polyphosphate, and melamine as factors. The oil absorption and activation index were tested to determine the effect of titanate on the flame retardant additive. The pavement performance test was conducted to evaluate the effect of the flame retardant additive. Oxygen index test was conducted to confirm the effect of flame retardant on flame ability of asphalt binder. The results of this study showed that the new composite flame retardant is more effective in improving the compatibility between flame retardant and asphalt and reducing the limiting oxygen index of asphalt binder tested in this study.

  10. Dissecting 30 Doradus: Optical and Near Infrared Star Formation History of the starburst cluster NGC2070 from the Hubble Tarantula Treasury Project

    Science.gov (United States)

    Cignoni, Michele

    2015-08-01

    I will present new results on the star formation history of 30 Doradus in the Large Magellanic Cloud based on the panchromatic imaging survey Hubble Tarantula Treasury Project (HTTP). Here the focus is on the starburst cluster NGC2070. The star formation history is derived by comparing the deepest ever optical and NIR color-magnitude diagrams (CMDs) with state-of-the-art synthetic CMDs generated with the latest PARSEC models, which include all stellar phases from pre-main sequence (PMS) to post-main sequence. For the first time in this region we are able to measure the star formation using intermediate and low mass stars simultaneously. Our results suggest that NGC2070 experienced a prolonged activity. I will discuss the detailed star formation history, initial mass function and reddening distribution and how these relate to previous studies of this starburst region.

  11. Autoignition and flame stabilisation processes in turbulent non-premixed hot coflow flames

    NARCIS (Netherlands)

    Oldenhof , E.

    2012-01-01

    This dissertation examines stabilisation processes in turbulent non-premixed jet flames, created by injecting gaseous fuel into a co-flowing stream of hot, low-oxygen combustion products. Being able to predict whether and how a flame achieves stable and reliable combustion is a matter of great pract

  12. On the dynamics of flame edges in diffusion-flame/vortex interactions

    Energy Technology Data Exchange (ETDEWEB)

    Hermanns, Miguel; Linan, Amable [Departamento de Motopropulsion y Termofluidodinamica, Universidad Politecnica de Madrid, Pza. Cardenal Cisneros 3, 28040 Madrid (Spain); Vera, Marcos [Area de Mecanica de Fluidos, Universidad Carlos III de Madrid, 28911 Leganes (Spain)

    2007-04-15

    We analyze the local flame extinction and reignition of a counterflow diffusion flame perturbed by a laminar vortex ring. Local flame extinction leads to the appearance of flame edges separating the burning and extinguished regions of the distorted mixing layer. The dynamics of these edges is modeled based on previous numerical results, with heat release effects fully taken into account, which provide the propagation velocity of triple and edge flames in terms of the upstream unperturbed value of the scalar dissipation. The temporal evolution of the mixing layer is determined using the classical mixture fraction approach, with both unsteady and curvature effects taken into account. Although variable density effects play an important role in exothermic reacting mixing layers, in this paper the description of the mixing layer is carried out using the constant density approximation, leading to a simplified analytical description of the flow field. The mathematical model reveals the relevant nondimensional parameters governing diffusion-flame/vortex interactions and provides the parameter range for the more relevant regime of local flame extinction followed by reignition via flame edges. Despite the simplicity of the model, the results show very good agreement with previously published experimental results. (author)

  13. Methane Formation by Flame-Generated Hydrogen Atoms in the Flame Ionization Detector

    DEFF Research Database (Denmark)

    Holm, Torkil; Madsen, Jørgen Øgaard

    1996-01-01

    The precombustion degradation of organic compounds in the flame ionization detector has been studied (1) by heating the additives in hydrogen in a quartz capillary and analyzing the reaction products by GC and (2) by following the degradation of the additives in a hydrogen flame, by means of a th...

  14. Modeling Candle Flame Behavior In Variable Gravity

    Science.gov (United States)

    Alsairafi, A.; Tien, J. S.; Lee, S. T.; Dietrich, D. L.; Ross, H. D.

    2003-01-01

    The burning of a candle, as typical non-propagating diffusion flame, has been used by a number of researchers to study the effects of electric fields on flame, spontaneous flame oscillation and flickering phenomena, and flame extinction. In normal gravity, the heat released from combustion creates buoyant convection that draws oxygen into the flame. The strength of the buoyant flow depends on the gravitational level and it is expected that the flame shape, size and candle burning rate will vary with gravity. Experimentally, there exist studies of candle burning in enhanced gravity (i.e. higher than normal earth gravity, g(sub e)), and in microgravity in drop towers and space-based facilities. There are, however, no reported experimental data on candle burning in partial gravity (g model of the candle flame, buoyant forces were neglected. The treatment of momentum equation was simplified using a potential flow approximation. Although the predicted flame characteristics agreed well with the experimental results, the model cannot be extended to cases with buoyant flows. In addition, because of the use of potential flow, no-slip boundary condition is not satisfied on the wick surface. So there is some uncertainty on the accuracy of the predicted flow field. In the present modeling effort, the full Navier-Stokes momentum equations with body force term is included. This enables us to study the effect of gravity on candle flames (with zero gravity as the limiting case). In addition, we consider radiation effects in more detail by solving the radiation transfer equation. In the previous study, flame radiation is treated as a simple loss term in the energy equation. Emphasis of the present model is on the gas-phase processes. Therefore, the detailed heat and mass transfer phenomena inside the porous wick are not treated. Instead, it is assumed that a thin layer of liquid fuel coated the entire wick surface during the burning process. This is the limiting case that the mass

  15. The VIMOS VLT Deep Survey :Evolution of the major merger rate since z~1 from spectroscopicaly confirmed galaxy pairs

    CERN Document Server

    de Ravel, L; Tresse, L; Bottini, D; Garilli, B; Le Brun, V; MacCagni, D; Scaramella, R; Scodeggio, M; Vettolani, G; Zanichelli, A; Adami, C; Arnouts, S; Bardelli, S; Bolzonella, M; Cappi, A; Charlot, S; Ciliegi, P; Contini, T; Foucaud, S; Franzetti, P; Gavignaud, I; Guzzo, L; Ilbert, O; Iovino, A; Lamareille, F; McCracken, H J; Marano, B; Marinoni, C; Mazure, A; Meneux, B; Merighi, R; Paltani, S; Pellò, R; Pollo, A; Pozzetti, L; Radovich, M; Vergani, D; Zamorani, G; Zucca, E; Bondi, M; Bongiorno, A; Brinchmann, J; Cucciati, O; De la Torre, S; Gregorini, L; Memeo, P; Pérez-Montero, E; Mellier, Y; Merluzzi, P; Temporin, S

    2008-01-01

    From the VIMOS VLT Deep Survey we use a sample of 6447 galaxies with I_{AB} 9.5 has been accreted through major merging events since z ~ 1, indicating that major mergers have contributed significantly to the growth in stellar mass density of bright galaxies over the last half of the life of the Universe.

  16. The Great Observatories Origins Deep Survey VLT/FORS2 spectroscopy in the GOODS-South Field

    NARCIS (Netherlands)

    Vanzella, E; Cristiani, S; Dickinson, M; Kuntschner, H; Moustakas, LA; Nonino, M; Rosati, P; Stern, D; Cesarsky, C; Ettori, S; Ferguson, HC; Fosbury, RAE; Giavalisco, M; Haase, J; Renzini, A; Rettura, A; Serra, P

    2005-01-01

    We present the first results of the ESO/ GOODS program of spectroscopy of faint galaxies in the Chandra Deep Field South ( CDF- S). 399 spectra of 303 unique targets have been obtained in service mode with the FORS2 spectrograph at the ESO/ VLT, providing 234 redshift determinations ( the median of

  17. The VLT LBG Redshift Survey - I. Clustering and dynamics of approximate to 1000 galaxies at z approximate to 3

    NARCIS (Netherlands)

    Bielby, R. M.; Shanks, T.; Weilbacher, P. M.; Infante, L.; Crighton, N. H. M.; Bornancini, C.; Bouche, N.; Heraudeau, P.; Lambas, D. G.; Lowenthal, J.; Minniti, D.; Padilla, N.; Petitjean, P.; Theuns, T.

    2011-01-01

    We present the initial imaging and spectroscopic data acquired as part of the Very Large Telescope (VLT) VIMOS Lyman-break galaxy Survey. UBR (or UBVI) imaging covers five approximate to 36 x 36 arcmin(2) fields centred on bright z > 3 quasi-stellar objects (QSOs), allowing approximate to 21 000 2 <

  18. X-shooter: UV-to-IR intermediate-resolution high-efficiency spectrograph for the ESO VLT

    NARCIS (Netherlands)

    D'Odorico, S.; Andersen, M.I.; Conconi, P.; De Caprio, V.; Delabre, B.; Di Marcantonio, P.; Dekker, H.; Downing, M.D.; Finger, G.; Groot, P.; Hanenburg, H.H.; Hammer, F.; Horville, D.; Hjorth, J.; Kaper, L.; Klougart, J.; Kjaergaard-Rasmussen, P.; Lizon, J.-L.; Marteaud, M.; Mazzoleni, R.; Michaelsen, N.; Pallavicini, R.; Rigal, F.; Santin, P.; Norup Soerensen, A.; Spano, P.; Venema, L.; Vola, P.; Zerbi, F.M.; Hasinger, G.; Turner, M.J.L.

    2004-01-01

    X-shooter is a single target spectrograph for the Cassegrain focus of one of the VLT UTs. It covers in a single exposure the spectral range from the UV to the H band with a possible extension into part of the K band. It is designed to maximize the sensitivity in this spectral range through the

  19. Design, analysis and testing of the Optical Tube Assemblies for the ESO VLT Four Laser Guide Star Facility

    NARCIS (Netherlands)

    Henselmans, R.; Nijkerk, M.D.; Lemmen, M.H.J.; Rijnveld, N.; Kamphues, F.G.

    2012-01-01

    TNO has developed the Optical Tube Assemblies (OTAs) for the ESO VLT Four Laser Guide Star Facility. The OTAs are Galilean 20x beam expanders, expanding a ∅15 mm input beam (25W, 589 nm CW) to a steerable ∅300 mm output beam. TNO has recently successfully completed acceptance testing of the four uni

  20. Turbulence-flame interactions in DNS of a laboratory high Karlovitz premixed turbulent jet flame

    Science.gov (United States)

    Wang, Haiou; Hawkes, Evatt R.; Chen, Jacqueline H.

    2016-09-01

    In the present work, direct numerical simulation (DNS) of a laboratory premixed turbulent jet flame was performed to study turbulence-flame interactions. The turbulent flame features moderate Reynolds number and high Karlovitz number (Ka). The orientations of the flame normal vector n, the vorticity vector ω and the principal strain rate eigenvectors ei are examined. The in-plane and out-of-plane angles are introduced to quantify the vector orientations, which also measure the flame geometry and the vortical structures. A general observation is that the distributions of these angles are more isotropic downstream as the flame and the flow become more developed. The out-of-plane angle of the flame normal vector, β, is a key parameter in developing the correction of 2D measurements to estimate the corresponding 3D quantities. The DNS results show that the correction factor is unity at the inlet and approaches its theoretical value of an isotropic distribution downstream. The alignment characteristics of n, ω and ei, which reflect the interactions of turbulence and flame, are also studied. Similar to a passive scalar gradient in non-reacting flows, the flame normal has a tendency to align with the most compressive strain rate, e3, in the flame, indicating that turbulence contributes to the production of scalar gradient. The vorticity dynamics are examined via the vortex stretching term, which was found to be the predominant source of vorticity generation balanced by dissipation, in the enstrophy transport equation. It is found that although the vorticity preferentially aligns with the intermediate strain rate, e2, the contribution of the most extensive strain rate, e1, to vortex stretching is comparable with that of the intermediate strain rate, e2. This is because the eigenvalue of the most extensive strain rate, λ1, is always large and positive. It is confirmed that the vorticity vector is preferentially positioned along the flame tangential plane, contributing

  1. Direct exoplanet detection and characterization using the ANDROMEDA method: Performance on VLT/NaCo data

    Science.gov (United States)

    Cantalloube, F.; Mouillet, D.; Mugnier, L. M.; Milli, J.; Absil, O.; Gomez Gonzalez, C. A.; Chauvin, G.; Beuzit, J.-L.; Cornia, A.

    2015-10-01

    Context. The direct detection of exoplanets with high-contrast imaging requires advanced data processing methods to disentangle potential planetary signals from bright quasi-static speckles. Among them, angular differential imaging (ADI) permits potential planetary signals with a known rotation rate to be separated from instrumental speckles that are either statics or slowly variable. The method presented in this paper, called ANDROMEDA for ANgular Differential OptiMal Exoplanet Detection Algorithm, is based on a maximum likelihood approach to ADI and is used to estimate the position and the flux of any point source present in the field of view. Aims: In order to optimize and experimentally validate this previously proposed method, we applied ANDROMEDA to real VLT/NaCo data. In addition to its pure detection capability, we investigated the possibility of defining simple and efficient criteria for automatic point source extraction able to support the processing of large surveys. Methods: To assess the performance of the method, we applied ANDROMEDA on VLT/NaCo data of TYC-8979-1683-1 which is surrounded by numerous bright stars and on which we added synthetic planets of known position and flux in the field. In order to accommodate the real data properties, it was necessary to develop additional pre-processing and post-processing steps to the initially proposed algorithm. We then investigated its skill in the challenging case of a well-known target, β Pictoris, whose companion is close to the detection limit and we compared our results to those obtained by another method based on principal component analysis (PCA). Results: Application on VLT/NaCo data demonstrates the ability of ANDROMEDA to automatically detect and characterize point sources present in the image field. We end up with a robust method bringing consistent results with a sensitivity similar to the recently published algorithms, with only two parameters to be fine tuned. Moreover, the companion flux

  2. Structure of Flame Balls at Low Lewis-Number

    Science.gov (United States)

    Weiland, Karen J.; Ronney, Paul

    1998-01-01

    The Structure of Flame Balls at Low Lewis-Number (SOFBALL) experiment explored the behavior of a newly discovered flame phenomena called "flame balls." These spherical, stable, stationary flame structures, observed only in microgravity, provide a unique opportunity to study the interactions of the two most important processes necessary for combustion (chemical reaction and heat and mass transport) in the simplest possible configuration. The previously unobtainable experimental data provided a comparison with models of flame stability and flame propagation limits that are crucial both in assessing fire safety and in designing efficient, clean-burning combustion engines.

  3. Flame Quenching Dynamics of High Velocity Flames in Rectangular Cross-section Channels

    KAUST Repository

    Mahuthannan, Ariff Magdoom

    2017-01-05

    Understanding flame quenching for different conditions is necessary to develop safety devices like flame arrestors. In practical applications, the speed of a deflagration in the lab-fixed reference frame will be a strong function of the geometry through which the deflagration propagates. This study reports on the effect of the flame speed, at the entrance of a quenching section, on the quenching distance. A 2D rectangular channel joining two main spherical vessels is considered for studying this effect. Two different velocity regimes are investigated and referred to as configurations A, and B. For configuration A, the velocity of the flame is 20 m/s, while it is about 100 m/s for configuration B. Methane-air stoichiometric mixtures at 1 bar and 298 K are used. Simultaneous dynamic pressure measurements along with schlieren imaging are used to analyze the quenching of the flame. Risk assessment of re-ignition is also reported and analyzed.

  4. Engineering Flame Retardant Biodegradable Nanocomposites

    Science.gov (United States)

    He, Shan; Yang, Kai; Guo, Yichen; Zhang, Linxi; Pack, Seongchan; Davis, Rachel; Lewin, Menahem; Ade, Harald; Korach, Chad; Kashiwagi, Takashi; Rafailovich, Miriam

    2013-03-01

    Cellulose-based PLA/PBAT polymer blends can potentially be a promising class of biodegradable nanocomposites. Adding cellulose fiber reinforcement can improve mechanical properties of biodegradable plastics, but homogeneously dispersing hydrophilic cellulose in the hydrophobic polymer matrix poses a significant challenge. We here show that resorcinol diphenyl phosphates (RDP) can be used to modify the surface energy, not only reducing phase separation between two polymer kinds but also allowing the cellulose particles and the Halloysite clay to be easily dispersed within polymer matrices to achieve synergy effect using melt blending. Here in this study we describe the use of cellulose fiber and Halloysite clay, coated with RDP surfactant, in producing the flame retardant polymer blends of PBAT(Ecoflex) and PLA which can pass the stringent UL-94 V0 test. We also utilized FTIR, SEM and AFM nanoindentation to elucidate the role RDP plays in improving the compatibility of biodegradable polymers, and to determine structure property of chars that resulted in composites that could have optimized mechanical and thermal properties. Supported by Garcia Polymer Center and NSF Foundation.

  5. A, a Brominated Flame Retardant

    Directory of Open Access Journals (Sweden)

    Tomomi Takeshita

    2013-01-01

    Full Text Available Tetrabromobisphenol A (TBBPA, a brominated flame retardant, has been found to exacerbate pneumonia in respiratory syncytial virus- (RSV- infected mice. We examined the effect of Brazilian propolis (AF-08 on the exacerbation of RSV infection by TBBPA exposure in mice. Mice were fed a powdered diet mixed with 1% TBBPA alone, 0.02% AF-08 alone, or 1% TBBPA and 0.02% AF-08 for four weeks and then intranasally infected with RSV. TBBPA exposure increased the pulmonary virus titer and level of IFN-γ, a representative marker of pneumonia due to RSV infection, in the lungs of infected mice without toxicity. AF-08 was significantly effective in reducing the virus titers and IFN-γ level increased by TBBPA exposure. Also, AF-08 significantly reduced proinflammatory cytokine (TNF-α and IL-6 levels in the lungs of RSV-infected mice with TBBPA exposure, but Th2 cytokine (IL-4 and IL-10 levels were not evidently increased. Neither TBBPA exposure nor AF-08 treatment affected the anti-RSV antibody production in RSV-infected mice. In flow cytometry analysis, AF-08 seemed to be effective in reducing the ratio of pulmonary CD8a+ cells in RSV-infected mice with TBBPA exposure. TBBPA and AF-08 did not exhibit anti-RSV activity in vitro. Thus, AF-08 probably ameliorated pneumonia exacerbated by TBBPA exposure in RSV-infected mice by limiting excess cellular immune responses.

  6. Sooting turbulent jet flame: characterization and quantitative soot measurements

    Science.gov (United States)

    Köhler, M.; Geigle, K. P.; Meier, W.; Crosland, B. M.; Thomson, K. A.; Smallwood, G. J.

    2011-08-01

    Computational fluid dynamics (CFD) modelers require high-quality experimental data sets for validation of their numerical tools. Preferred features for numerical simulations of a sooting, turbulent test case flame are simplicity (no pilot flame), well-defined boundary conditions, and sufficient soot production. This paper proposes a non-premixed C2H4/air turbulent jet flame to fill this role and presents an extensive database for soot model validation. The sooting turbulent jet flame has a total visible flame length of approximately 400 mm and a fuel-jet Reynolds number of 10,000. The flame has a measured lift-off height of 26 mm which acts as a sensitive marker for CFD model validation, while this novel compiled experimental database of soot properties, temperature and velocity maps are useful for the validation of kinetic soot models and numerical flame simulations. Due to the relatively simple burner design which produces a flame with sufficient soot concentration while meeting modelers' needs with respect to boundary conditions and flame specifications as well as the present lack of a sooting "standard flame", this flame is suggested as a new reference turbulent sooting flame. The flame characterization presented here involved a variety of optical diagnostics including quantitative 2D laser-induced incandescence (2D-LII), shifted-vibrational coherent anti-Stokes Raman spectroscopy (SV-CARS), and particle image velocimetry (PIV). Producing an accurate and comprehensive characterization of a transient sooting flame was challenging and required optimization of these diagnostics. In this respect, we present the first simultaneous, instantaneous PIV, and LII measurements in a heavily sooting flame environment. Simultaneous soot and flow field measurements can provide new insights into the interaction between a turbulent vortex and flame chemistry, especially since soot structures in turbulent flames are known to be small and often treated in a statistical manner.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-11-20

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

  8. Status and new operation modes of the versatile VLT/NACO

    CERN Document Server

    Girard, Julien H V; Quanz, Sascha P; Kenworthy, Matthew A; Rengaswamy, Sridharan; Schödel, Rainer; Gallenne, Alexandre; Gillessen, Stefan; Huerta, Nicolas; Kervella, Pierre; Kornweibel, Nick; Lenzen, Rainer; Mérand, Antoine; Montagnier, Guillaume; O'Neal, Jared; Zins, Gérard; IOT, the NACO; 10.1117/12.856799

    2010-01-01

    This paper aims at giving an update on the most versatile adaptive optics fed instrument to date, the well known and successful NACO . Although NACO is only scheduled for about two more years at the Very Large Telescope (VLT), it keeps on evolving with additional operation modes bringing original astronomical results. The high contrast imaging community uses it creatively as a test-bench for SPHERE and other second generation planet imagers. A new visible wavefront sensor (WFS) optimized for Laser Guide Star (LGS) operations has been installed and tested, the cube mode is more and more requested for frame selection on bright sources, a seeing enhancer mode (no tip/tilt correction) is now offered to provide full sky coverage and welcome all kind of extragalactic applications, etc. The Instrument Operations Team (IOT) and Paranal engineers are currently working hard at maintaining the instrument overall performances but also at improving them and offering new capabilities, providing the community with a well tu...

  9. Developing an instrument simulator: experience feedback from the JWST/NIRSpec and VLT/MUSE simulators

    Science.gov (United States)

    Jarno, Aurélien; Piqueras, Laure; Bacon, Roland; Ferruit, Pierre; Legros, Emeline; Pécontal-Rousset, Arlette; Gnata, Xavier; Streicher, Ole; Weilbacher, Peter

    2012-09-01

    The Centre de Recherche Astrophysique de Lyon (CRAL) has recently developed two instrument simulators for spectrographic instruments. They are based on Fourier optics, and model the whole chain of acquisition, taking into account both optical aberrations and diffraction effects, by propagating a wavefront through the instrument, according to the Fourier optics concept. One simulates the NIRSpec instrument, a near-infrared multi-object spectrograph for the future James Webb Space Telescope (JWST). The other one models the Multi Unit Spectroscopic Explorer (MUSE) instrument, a second-generation integral-field spectrograph for the Very Large Telescope (VLT). The two simulators have been developed in different contexts (subcontracted versus developed internally), and for very different instruments (space-based versus ground-based), which strengthen the CRAL experience. This paper describes the lessons learned while developing these simulators: development methods, phasing with the project, points to focus on, getting data, interacting with scientists and users, etc.

  10. Revealing deuterium Balmer lines in HII regions with VLT-UVES

    CERN Document Server

    Hébrard, G; Walsh, J R; Vidal-Madjar, A; Ferlet, R

    2000-01-01

    The search for deuterium Balmer lines with VLT-UVES is reported in HII regions of the Galaxy and the Magellanic Clouds. The DI lines appear as faint, narrow emission features in the blue wings of the HI Balmer lines and can be distinguished from high-velocity HI emission. The previous identification to deuterium is re-inforced beyond doubt. The detection of D-alpha and D-beta in Orion (Hebrard et al. 2000) is confirmed and deuterium lines are now detected up to at least D-eta. The UVES observations provide the first detection of Balmer DI lines in four new HII regions (M 8, M 16, M 20, and DEM S 103 in SMC), demonstrating that these lines are of common occurence.

  11. Validation Through Simulations of a Cn2 Profiler for the ESO/VLT Adaptive Optics Facility

    CERN Document Server

    Garcia-Rissmann, A; Kolb, J; Louarn, M Le; Madec, P -Y; Neichel, B

    2015-01-01

    The Adaptive Optics Facility (AOF) project envisages transforming one of the VLT units into an adaptive telescope and providing its ESO (European Southern Observatory) second generation instruments with turbulence corrected wavefronts. For MUSE and HAWK-I this correction will be achieved through the GALACSI and GRAAL AO modules working in conjunction with a 1170 actuators Deformable Secondary Mirror (DSM) and the new Laser Guide Star Facility (4LGSF). Multiple wavefront sensors will enable GLAO and LTAO capabilities, whose performance can greatly benefit from a knowledge about the stratification of the turbulence in the atmosphere. This work, totally based on end-to-end simulations, describes the validation tests conducted on a Cn2 profiler adapted for the AOF specifications. Because an absolute profile calibration is strongly dependent on a reliable knowledge of turbulence parameters r0 and L0, the tests presented here refer only to normalized output profiles. Uncertainties in the input parameters inherent t...

  12. NIX, the imager for ERIS: the AO instrument for the VLT

    Science.gov (United States)

    Pearson, David; Taylor, William; Davies, Ric; MacIntosh, Mike; Henry, David; Lunney, David; Waring, Chris; Gao, Xiaofeng; Lightfoot, John; Glauser, Adrian M.; Quanz, Sascha P.; Meyer, Michael R.; Schmid, Hans Martin; March, Stephen; Bachmann, Walter; Feuchtgruber, Helmut; George, Elizabeth; Sturm, Eckhard; Biller, Beth; Hinckley, Sasha; Kenworthy, Matthew; Amico, Paola; Glindemann, Andreas; Kasper, Marcus; Kuntschner, Harald; Dorn, Reinhold; Egner, Sebastian

    2016-08-01

    ERIS will be the next-generation AO facility on the VLT, combining the heritage of NACO imaging, with the spectroscopic capabilities of an upgraded SINFONI. Here we report on the all-new NIX imager that will deliver diffraction-limited imaging from the J to M band. The instrument will be equipped with both Apodizing Phase Plates and Sparse Aperture Masks to provide high-angular resolution imagery, especially suited for exoplanet imaging and characterization. This paper provides detail on the instrument's design and how it is suited to address a broad range of science cases, from detailed studies of the galactic centre at the highest resolutions, to studying detailed resolved stellar populations.

  13. VLT transit and occultation photometry for the bloated planet CoRoT-1b

    CERN Document Server

    Gillon, M; Triaud, A H M J; Barman, T; Hebb, L; Montalban, J; Maxted, P F L; Queloz, D; Deleuil, M; Magain, P

    2009-01-01

    We present VLT eclipse photometry for the giant planet CoRoT-1b. We observed a transit in the R-band filter and an occultation in a narrow filter centered on 2.09 microns. Our analysis of this new photometry and published radial velocities, in combination with stellar-evolutionary modeling, leads to a planetary mass and radius of 1.07 (+0.13,-0.18) M_Jup and 1.45 (+0.07,-0.13) R_Jup, confirming the very low density previously deduced from CoRoT photometry. The large occultation depth that we measure at 2.09 microns (0.278 (+0.043,-0.066) %) is consistent with thermal emission and is better reproduced by an atmospheric model with no redistribution of the absorbed stellar flux to the night side of the planet.

  14. Mid-IR observations of NGC 1068 with VLT/VISIR

    CERN Document Server

    Poncelet, A; Perrin, G; Sol, H; Lagage, P O

    2006-01-01

    We present a speckle analysis of the active galactic nucleus (AGN) inside the archetype Seyfert type 2 galaxy NGC 1068. This study is based on 12.8 microns images obtained with the burst mode of VISIR (the Very Large Telescope Imager and Spectrometer in the InfraRed). The interferometric processing allows to push the resolution far below the diffraction limit of a 8m telescope in the N-band and to trace two main contributions to the mid-IR flux inside the nucleus. It also allows to partially fill the lack of visibility points at low spatial frequencies. The confrontation with VLT/MIDI (the Mid-InfrareD Interferometer) data points helps to establish the link between dust in the vicinity of the central engine and inside the ionisation cone to get a multi-scale picture of mid-IR sources emitting in the nucleus of NGC 1068.

  15. The Space Missions WAXS/WFXT and SWIFT New Targets for the VLT

    CERN Document Server

    Chincarini, G L

    1999-01-01

    At OAB we were, during the year 1998, deeply involved in planning two important space missions for which very large ground based telescopes, VLT in particular, would play a very large and important role in the optical followup. The study of the first mission, Wide Angle X-ray Survey using a Wide Field X-ray Telescope, was coordinated by the Observatory of Brera, involved mainly Italian industries and resulted in a proposal to the Italian Space Agency under the Small Satellite Program. The second mission, SWIFT, has been coordinated and directed by the Goddard Space Flight Center and resulted in the submission of a proposal to NASA under the MIDEX program. The science goal of this mission is the detection and study of the Gamma-ray bursts.

  16. Direct exoplanet detection and characterization using the ANDROMEDA method: Performance on VLT/NaCo data

    CERN Document Server

    Cantalloube, F; Mugnier, L M; Milli, J; Absil, O; Gonzalez, C A Gomez; Chauvin, G; Beuzit, J -L; Cornia, A

    2015-01-01

    Context. The direct detection of exoplanets with high-contrast imaging requires advanced data processing methods to disentangle potential planetary signals from bright quasi-static speckles. Among them, angular differential imaging (ADI) permits potential planetary signals with a known rotation rate to be separated from instrumental speckles that are either statics or slowly variable. The method presented in this paper, called ANDROMEDA for ANgular Differential OptiMal Exoplanet Detection Algorithm is based on a maximum likelihood approach to ADI and is used to estimate the position and the flux of any point source present in the field of view. Aims. In order to optimize and experimentally validate this previously proposed method, we applied ANDROMEDA to real VLT/NaCo data. In addition to its pure detection capability, we investigated the possibility of defining simple and efficient criteria for automatic point source extraction able to support the processing of large surveys. Methods. To assess the performan...

  17. The binarity status of stars with and without planets Probed with vlt/naco

    Directory of Open Access Journals (Sweden)

    S. Udry

    2004-01-01

    Full Text Available Las propiedades de los planetas en orbita alrededor de una componente de una estrella binaria o m ultiple son distintas a las de los planetas de las estrellas aisladas (Udry et al., 2004. Describimos un sondeo con la optica adaptativa VLT/NACO que intenta estudiar el efecto de la duplicidad estelar en la formaci on y evoluci on de los planetas, comparando la estad stica de las compa~neras d ebiles en muestras de estrellas con y sin planetas, seleccionadas en forma similar. Los resultados nos permitir an discriminar entre los modelos para la formaci on de planetas (acreci on o inestabilidad del disco. Los resultados preliminares son muy interesantes: el 20 7% de las estrellas \\sencillas" tienen compa~neras dentro de 1000, mientras que s olo el 3 3% de compa~neras equivalentes se encuentran cerca de las estrellas que albergan.

  18. Deep census of variable stars in a VLT/VIMOS field in Carina

    CERN Document Server

    Pietrukowicz, P; Fernández, J M; Pietrzynski, G; Ruiz, M T; Gieren, W; Diaz, R F; Zoccali, M; Hempel, M

    2009-01-01

    We have searched for variable stars in deep V-band images of a field towards the Galactic plane in Carina. The images were taken with VIMOS instrument at ESO VLT during 4 contiguous nights in April 2005. We detected 348 variables among 50897 stars in the magnitude range between V=15.4 and V=24.5 mag. Upon detection, we classified the variables by direct eye inspection of their light curves. All variable objects but 9 OGLE transits in the field are new discoveries. We provide a complete catalog of all variables which includes eclipsing/ellipsoidal binaries, miscellaneous pulsators (mostly delta Scuti-type variables), stars with flares and other (irregular and likely long-period) variables. Only two of the stars in our sample are known to host planets. Our result give some implications for future large variability surveys.

  19. Close Companions to Nearby Young Stars from Adaptive Optics Imaging on VLT and Keck

    Science.gov (United States)

    Haisch, Karl E.; Jayawardhana, Ray; Brandeker, Alexis; Mardones, Diego

    We report the results of VLT and Keck adaptive optics surveys of known members of the η Chamaeleontis, MBM 12, and TW Hydrae (TWA) associations to search for close companions. The multiplicity statistics of η Cha, MBM 12, and TWA are quite high compared with other clusters and associations, although our errors are large due to small number statistics. We have resolved S18 in MBM 12 and RECX 9 in η Cha into triples for the first time. The tight binary TWA 5Aab in the TWA offers the prospect of measuring the dynamical masses of both components as well as an independent distance to the system within a few years. The AO detection of the close companion to the nearby young star χ1 Orionis, previously inferred from radial velocity and astrometric observations, has already made it possible to derive the dynamical masses of that system without any astrophysical assumption.

  20. Close Companions to Nearby Young Stars from Adaptive Optics Imaging on VLT and Keck

    CERN Document Server

    Haisch, K E; Brandeker, A; Mardones, D; Jr., Karl E. Haisch; Jayawardhana, Ray; Brandeker, Alexis; Mardones, Diego

    2003-01-01

    We report the results of VLT and Keck adaptive optics surveys of known members of the Eta Chamaeleontis, MBM 12, and TW Hydrae (TWA) associations to search for close companions. The multiplicity statistics of Eta Cha, MBM 12, and TWA are quite high compared with other clusters and associations, although our errors are large due to small number statistics. We have resolved S18 in MBM 12 and RECX 9 in Eta Cha into triples for the first time. The tight binary TWA 5Aab in the TWA offers the prospect of measuring the dynamical masses of both components as well as an independent distance to the system within a few years. The AO detection of the close companion to the nearby young star Chi^1 Orionis, previously inferred from radial velocity and astrometric observations, has already made it possible to derive the dynamical masses of that system without any astrophysical assumption.

  1. VLT/UVES constraints on the cosmological variability of the fine-structure constant

    Science.gov (United States)

    Levshakov, S. A.; Centurión, M.; Molaro, P.; D'Odorico, S.

    2005-05-01

    We propose a new methodology for probing the cosmological variability of α from pairs of Fe II lines (SIDAM, single ion differential α measurement) observed in individual exposures from a high resolution spectrograph. By this we avoid the influence of the spectral shifts due to (i) ionization inhomogeneities in the absorbers; and (ii) non-zero offsets between different exposures. Applied to the Fe II lines of the metal absorption line system at z_abs = 1.839 in the spectrum of Q 1101-264 obtained by means of the UV-Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT), SIDAM provides Δα/α = (2.4±3.8_stat)×10-6. The z_abs = 1.15 Fe II system toward HE 0515-4414 has been re-analyzed by this method thus obtaining for the combined sample Δα/α = (0.4±1.5_stat)×10-6. These values are shifted with respect to the Keck/HIRES mean Δα/α = (-5.7 ± 1.1_stat)×10-6 (Murphy et al. 2004) at very high confidence level (95%). The fundamental photon noise limitation in the Δα/α measurement with the VLT/UVES is discussed to figure the prospects for future observations. It is suggested that with a spectrograph of ~10 times the UVES dispersion coupled to a 100 m class telescope the present Oklo level (Δα/α ≥ 4.5 × 10-8) can be achieved along cosmological distances with differential measurements of Δα/α.

  2. Launch Pad Flame Trench Refractory Materials

    Science.gov (United States)

    Calle, Luz M.; Hintze, Paul E.; Parlier, Christopher R.; Bucherl, Cori; Sampson, Jeffrey W.; Curran, Jerome P.; Kolody, Mark; Perusich, Steve; Whitten, Mary

    2010-01-01

    The launch complexes at NASA's John F. Kennedy Space Center (KSC) are critical support facilities for the successful launch of space-based vehicles. These facilities include a flame trench that bisects the pad at ground level. This trench includes a flame deflector system that consists of an inverted, V-shaped steel structure covered with a high temperature concrete material five inches thick that extends across the center of the flame trench. One side of the "V11 receives and deflects the flames from the orbiter main engines; the opposite side deflects the flames from the solid rocket boosters. There are also two movable deflectors at the top of the trench to provide additional protection to shuttle hardware from the solid rocket booster flames. These facilities are over 40 years old and are experiencing constant deterioration from launch heat/blast effects and environmental exposure. The refractory material currently used in launch pad flame deflectors has become susceptible to failure, resulting in large sections of the material breaking away from the steel base structure and creating high-speed projectiles during launch. These projectiles jeopardize the safety of the launch complex, crew, and vehicle. Post launch inspections have revealed that the number and frequency of repairs, as well as the area and size of the damage, is increasing with the number of launches. The Space Shuttle Program has accepted the extensive ground processing costs for post launch repair of damaged areas and investigations of future launch related failures for the remainder of the program. There currently are no long term solutions available for Constellation Program ground operations to address the poor performance and subsequent failures of the refractory materials. Over the last three years, significant liberation of refractory material in the flame trench and fire bricks along the adjacent trench walls following Space Shuttle launches have resulted in extensive investigations of

  3. Chaotic radiation/turbulence interactions in flames

    Energy Technology Data Exchange (ETDEWEB)

    Menguec, M.P.; McDonough, J.M.

    1998-11-01

    In this paper, the authors present a review of their recent efforts to model chaotic radiation-turbulence interactions in flames. The main focus is to characterize soot volume fraction fluctuations in turbulent diffusion flames, as they strongly contribute to these interaction. The approach is based on the hypothesis that the fluctuations of properties in turbulent flames are deterministic in nature, rather than random. The authors first discuss the theoretical details and then they briefly outline the experiments conducted to measure the scattered light signals from fluctuating soot particles along the axis of an ethylene-air diffusion flame. They compare the power spectra and time series obtained from experiments against the ad-hoc and rigorous models derived using a series of logistic maps. These logistic maps can be used in simulation of the fluctuations in these type of flames, without extensive computational effort or sacrifice of physical detail. Availability of accurate models of these kinds allows investigation of radiation-turbulence interactions at a more fundamental level than it was previously possible.

  4. Second Law Analysis of Diffusion Flames

    Directory of Open Access Journals (Sweden)

    Yalcin Gogus

    2001-03-01

    Full Text Available The objective of this paper is to investigate the sources of volumetric irreversibilities in both laminar and turbulent diffusion flames. The theoretical background of analysis relies on the local exergy transport equation, which allows the microscopic formulation of the well-known Gouy-Stodola theorem. For laminar reacting flows, the volumetric entropy generation rate expression includes the viscous, thermal, diffusion and chemical components. Their expressions show that the corresponding irreversibilities are uncoupled if the combustion process occurs at constant pressure. The numerical simulation of a methane-air combustion process shows that the thermal, chemical and diffusive irreversibilities represent, in order of enumeration, the predominant irreversibilities in the laminar diffusion reacting flows. In the case of turbulent diffusion flames, the viscous, thermal, diffusion and chemical mean components have to be expressed in accordance with the combustion model. Two combustion models are used: the multi-species approach based on the eddy-break formulation of mean reaction rate, and the assumed probability density function for a conserved scalar that relies on the flame sheet model. For a diffusion methane-air jet flame, the distribution of mean irreversibility components is presented. Taking into account the technical importance of diffusion flames, the analysis could serve to improve the combustion geometry and the flow condition.

  5. Aromatics oxidation and soot formation in flames

    Energy Technology Data Exchange (ETDEWEB)

    Howard, J.B.; Pope, C.J.; Shandross, R.A.; Yadav, T.

    1993-04-01

    This project is concerned with the kinetics and mechanisms of aromatics oxidation and soot and fullerenes formation in flames. The scope includes detailed measurements of profiles of stable and radical species concentrations in low-pressure one-dimensional premixed flames. Intermediate species identifications and mole fractions, fluxes, and net reaction rates calculated from the measured profiles are used to test postulated reaction mechanisms. Particular objectives are to identify, and to confirm or determine rate constants for, the main benzene oxidation reactions in flames, and to characterize soot and fullerenes and their formation mechanisms and kinetics. Stable and radical species profiles in the aromatics oxidation study are measured using molecular beam sampling with on-line mass spectrometry. The rate of soot formation measured by conventional optical techniques is found to support the hypotheses that particle inception occurs through reactive coagulation of high molecular weight PAH in competition with destruction by OHattack, and that the subsequent growth of the soot mass occurs through addition reactions of PAH and C[sub 2]H[sub 2] with the soot particles. During the first year of this reporting period, fullerenes C[sub 60] and C[sub 70] in substantial quantities were found in the flames being studied. The fullerenes were recovered, purified and spectroscopically identified. The yields of C[sub 60] and C[sub 70] were then determined over ranges of conditions in low-pressure premixed flames of benzene and oxygen.

  6. Distributed Flames in Type Ia Supernovae

    CERN Document Server

    Aspden, A J; Woosley, S E; 10.1088/0004-637X/710/2/1654

    2011-01-01

    In the distributed burning regime, turbulence disrupts the internal structure of the flame, and so the idea of laminar burning propagated by conduction is no longer valid. The nature of the burning depends on the turbulent Damkohler number (Da), which steadily declines from much greater than one to less that one as the density decreases to a few 10^6 g/cc. Scaling arguments predict that the turbulent flame speed s, normalized by the turbulent intensity u, follows s/u=Da^1/2 for Da1, and that localized excursions to as much as five times u can occur. The lambda-flame speed and width can be predicted based on the turbulence in the star and the turbulent nuclear burning time scale of the fuel. We propose a practical method for measuring these based on the scaling relations and small-scale computationally-inexpensive simulations. This suggests that a simple turbulent flame model can be easily constructed suitable for large-scale distributed supernovae flames.

  7. Pulsating instability and self-acceleration of fast turbulent flames

    CERN Document Server

    Poludnenko, A Y

    2015-01-01

    (Abridged) A series of three-dimensional numerical simulations is used to study the intrinsic stability of high-speed turbulent flames. Calculations model the interaction of a fully-resolved premixed flame with a highly subsonic, statistically steady, homogeneous, isotropic turbulence. We consider a wide range of turbulent intensities and system sizes, corresponding to the Damk\\"ohler numbers Da = 0.1-6.0. These calculations show that turbulent flames in the regimes considered are intrinsically unstable. In particular, we find three effects. 1) Turbulent flame speed develops pulsations with the observed peak-to-peak amplitude > 10 and a characteristic time scale close to a large-scale eddy turnover time. Such variability is caused by the interplay between turbulence, which continuously creates the flame surface, and highly intermittent flame collisions, which consume the flame surface. 2) Unstable burning results in the periodic pressure build-up and the formation of pressure waves or shocks, when the flame s...

  8. Beam steering effects in turbulent high pressure flames

    Energy Technology Data Exchange (ETDEWEB)

    Hemmerling, B.; Kaeppeli, B. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The propagation of a laser beam through a flame is influenced by variations of the optical density. Especially in turbulent high pressure flames this may seriously limit the use of laser diagnostic methods. (author) 1 fig., 2 refs.

  9. Daphnid life cycle response to new generation of flame retardants

    NARCIS (Netherlands)

    Waaijers, S.L.; Bleyenberg, T.E.; Dits, A; Schoorl, M.; Schütt, J; Kools, S.A.E.; de Voogt, P.; Admiraal, W.; Parsons, J.R.; Kraak, M.H.S.

    2013-01-01

    Relatively hazardous brominated flame retardants (BFRs) are currently substituted with halogen-free flame retardants (HFFRs). Consequently, information on their persistence, bioaccumulation and toxicity (PBT) is urgently needed. Therefore, we investigated the chronic toxicity to the water flea

  10. Visualization of ionic wind in laminar jet flames

    KAUST Repository

    Park, Daegeun

    2017-07-03

    Electric field, when it is applied to hydrocarbon flames, generates ionic wind due to the electric body force on charge carrying species. Ionic wind has been shown to influence soot emission, propagation speed, and stability of flames; however, a detailed behavior of ionic wind and its effects on flames is still not clear. Here, we investigated the dynamic behaviors of flames and ionic wind in the presence of direct current (DC) and alternating current (AC) electric fields in nonpremixed and premixed jet flames with a jet nozzle placed between two parallel electrodes. We observed a skewed flame toward a lower potential electrode with DC and lower frequency AC (e.g., 10Hz) and a steady flame with higher frequencies AC (1000Hz), while we found that the ionic wind blew toward both the anode and cathode regardless of flame type (nonpremixed or premixed) or the source of the electric field (DC and AC).

  11. The Interaction of High-Speed Turbulence with Flames: Turbulent Flame Speed

    CERN Document Server

    Poludnenko, Alexei Y; 10.1016/j.combustflame.2010.09.002

    2011-01-01

    (Abridged) Direct numerical simulations of the interaction of a premixed flame with driven, subsonic, homogeneous, isotropic, Kolmogorov-type turbulence in an unconfined system are used to study the mechanisms determining the turbulent flame speed, S_T, in the thin reaction zone regime. High intensity turbulence is considered with the r.m.s. velocity 35 times the laminar flame speed, S_L, resulting in the Damkohler number Da = 0.05. Here we show that: (1) The flame brush has a complex internal structure, in which the isosurfaces of higher fuel mass fractions are folded on progressively smaller scales. (2) Global properties of the turbulent flame are best represented by the structure of the region of peak reaction rate, which defines the flame surface. (3) In the thin reaction zone regime, S_T is predominantly determined by the increase of the flame surface area, A_T, caused by turbulence. (4) The observed increase of S_T relative to S_L exceeds the corresponding increase of A_T relative to the surface area of...

  12. Luminous Flame Temperature Distribution Measurement Using the Emission Method

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Flame temperature distribution is one of the most important characteristic parameters in combustion research. The emission method is a good way to measure the luminous flame temperature field. The maximum entropy method is introduced to the temperature distribution measurement of a luminous flame using the emission method. A simplified mathematical model was derived by combining the thermal radiation theory, reconstruction algorithm and maximum entropy method. Suitable parameters were selected in the computing process. Good experimental results were obtained with pulverized coal flames.

  13. CARS Temperature Measurements in Sooting, Laminar Diffusion Flames.

    Science.gov (United States)

    1984-07-30

    ethylene-air discussed above raise ques- tions about structure of a sooting flame and energy loss due to thermal radia- tion from soot. These questions do...certainly suggest that thermal radiation from soot may I, not be the only significant energy loss from a sooting flame . Nonluminous emission from CO2...CARS thermometry in a sooting flame . * Combust. Flame, 36, 87. Farrow, R. L., Lucht, R. P., Flower, W. L., and Palmer, R. E. (1984). Coherent anti

  14. Annealing effect and stability of carbon nanotubes in hydrogen flame

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Annealing of carbon nanotubes (CNTs) by the hydrogen flame in air was investigated in this study. Raman spectroscopy and scanning electron microscopy were used to characterize the products. The peak width of Raman spectra decreased with the increase in the annealing time. The CNTs were not stable in the hydrogen flame and the etching rate of the CNTs by hydrogen flame was very high. The hydrogen flame annealing had some effects on improving the crystallinity of CNTs.

  15. The Influences of Electric Fields on Soot Formation and Flame Structure of Diffusion Flames

    Institute of Scientific and Technical Information of China (English)

    LinXie; TakeyukiKishi; 等

    1993-01-01

    The influences of DC and AC electric fields,at frequencies up to 1.48 MHz and the maximum strength of about 6 kV/cm,on soot formation and flame structure were investigated using a counterflow type acetylene diffusion flame.The distributioons of flame luminosity,soot volume fraction,Flame temperature and OH concentration in flame were measured by non-invasive detection methods.Under the influence of electric fields,the changes in distribution of the soot volume fraction were confirmed.Electric fields of high frequency and high intensity reduced the soot volume fraction.whereas other electric fields increased it.The maximum values of flame temperature and OH concentration decreased.In the relationship between the maximum value of the soot volume fraction and the maximum temperature,the maximum soot volum fraction showed toth increase and decrease with maximum temperatures depending on the frequencies and intensities of the electric fields,and both of them occurred at temperatures lower than 1990 K.The production of the incipient particles seemed to be the dominant process controlling the soot volume fraction due to the electric fields.The luminosity of a sooting diffusion flame was found to depend on the volume fraction and temperature of the soot particles in the flame,As for the behavior of the flame in the electric fields.the ionic wind effect was not found to be dominant in the present work,and the result of the precious simulation based on the ionic wind theory was not consistent with the present experimental results.

  16. The Flame Challenge and Communicating Science

    Science.gov (United States)

    Ames, Ben

    2013-04-01

    When famed actor and science enthusiast Alan Alda was 11 years-old he was itching to know the science behind a flame. He asked his science teacher but her blunt response didn't exactly satisfy his curiosity. ``It's oxidation,'' she said. 65 years later, Alan Alda launched ``The Flame Challenge,'' an annual contest encouraging scientists to improve their communication to the general public. In this talk, last year's winner discusses his approach to successfully explaining the science behind a flame to a wide audience. Because communicating science is a pillar of the scientific method, he shares key elements of successful communication important for engaging funders, policy-makers, students, the general public, and even other scientists.

  17. Front roughening of flames in discrete media

    Science.gov (United States)

    Lam, Fredric; Mi, XiaoCheng; Higgins, Andrew J.

    2017-07-01

    The morphology of flame fronts propagating in reactive systems composed of randomly positioned, pointlike sources is studied. The solution of the temperature field and the initiation of new sources is implemented using the superposition of the Green's function for the diffusion equation, eliminating the need to use finite-difference approximations. The heat released from triggered sources diffuses outward from each source, activating new sources and enabling a mechanism of flame propagation. Systems of 40 000 sources in a 200 ×200 two-dimensional domain were tracked using computer simulations, and statistical ensembles of 120 realizations of each system were averaged to determine the statistical properties of the flame fronts. The reactive system of sources is parameterized by two nondimensional values: the heat release time (normalized by interparticle diffusion time) and the ignition temperature (normalized by adiabatic flame temperature). These two parameters were systematically varied for different simulations to investigate their influence on front propagation. For sufficiently fast heat release and low ignition temperature, the front roughness [defined as the root mean square deviation of the ignition temperature contour from the average flame position] grew following a power-law dependence that was in excellent agreement with the Kardar-Parisi-Zhang (KPZ) universality class (β =1 /3 ). As the reaction time was increased, lower values of the roughening exponent were observed, and at a sufficiently great value of reaction time, reversion to a steady, constant-width thermal flame was observed that matched the solution from classical combustion theory. Deviation away from KPZ scaling was also observed as the ignition temperature was increased. The features of this system that permit it to exhibit both KPZ and non-KPZ scaling are discussed.

  18. Large Scale Flame Spread Environmental Characterization Testing

    Science.gov (United States)

    Clayman, Lauren K.; Olson, Sandra L.; Gokoghi, Suleyman A.; Brooker, John E.; Ferkul, Paul V.; Kacher, Henry F.

    2013-01-01

    Under the Advanced Exploration Systems (AES) Spacecraft Fire Safety Demonstration Project (SFSDP), as a risk mitigation activity in support of the development of a large-scale fire demonstration experiment in microgravity, flame-spread tests were conducted in normal gravity on thin, cellulose-based fuels in a sealed chamber. The primary objective of the tests was to measure pressure rise in a chamber as sample material, burning direction (upward/downward), total heat release, heat release rate, and heat loss mechanisms were varied between tests. A Design of Experiments (DOE) method was imposed to produce an array of tests from a fixed set of constraints and a coupled response model was developed. Supplementary tests were run without experimental design to additionally vary select parameters such as initial chamber pressure. The starting chamber pressure for each test was set below atmospheric to prevent chamber overpressure. Bottom ignition, or upward propagating burns, produced rapid acceleratory turbulent flame spread. Pressure rise in the chamber increases as the amount of fuel burned increases mainly because of the larger amount of heat generation and, to a much smaller extent, due to the increase in gaseous number of moles. Top ignition, or downward propagating burns, produced a steady flame spread with a very small flat flame across the burning edge. Steady-state pressure is achieved during downward flame spread as the pressure rises and plateaus. This indicates that the heat generation by the flame matches the heat loss to surroundings during the longer, slower downward burns. One heat loss mechanism included mounting a heat exchanger directly above the burning sample in the path of the plume to act as a heat sink and more efficiently dissipate the heat due to the combustion event. This proved an effective means for chamber overpressure mitigation for those tests producing the most total heat release and thusly was determined to be a feasible mitigation

  19. Numerical modelling of ion transport in flames

    KAUST Repository

    Han, Jie

    2015-10-20

    This paper presents a modelling framework to compute the diffusivity and mobility of ions in flames. The (n, 6, 4) interaction potential is adopted to model collisions between neutral and charged species. All required parameters in the potential are related to the polarizability of the species pair via semi-empirical formulas, which are derived using the most recently published data or best estimates. The resulting framework permits computation of the transport coefficients of any ion found in a hydrocarbon flame. The accuracy of the proposed method is evaluated by comparing its predictions with experimental data on the mobility of selected ions in single-component neutral gases. Based on this analysis, the value of a model constant available in the literature is modified in order to improve the model\\'s predictions. The newly determined ion transport coefficients are used as part of a previously developed numerical approach to compute the distribution of charged species in a freely propagating premixed lean CH4/O2 flame. Since a significant scatter of polarizability data exists in the literature, the effects of changes in polarizability on ion transport properties and the spatial distribution of ions in flames are explored. Our analysis shows that changes in polarizability propagate with decreasing effect from binary transport coefficients to species number densities. We conclude that the chosen polarizability value has a limited effect on the ion distribution in freely propagating flames. We expect that the modelling framework proposed here will benefit future efforts in modelling the effect of external voltages on flames. Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/13647830.2015.1090018. © 2015 Taylor & Francis.

  20. 30 CFR 75.600-1 - Approved cables; flame resistance.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Approved cables; flame resistance. 75.600-1 Section 75.600-1 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE... cables; flame resistance. Cables shall be accepted or approved by MSHA as flame resistant....

  1. Preparation and characterizations of flame retardant polyamide 66 fiber

    Science.gov (United States)

    Li, Y. Y.; Liu, K.; Xiao, R.

    2017-06-01

    The polyamide 66 (PA66) is one of the most important thermoplastic materials, but it has the drawback of flammability. So the flame retardant PA66 was prepared by condensation polymerization using nylon salt and DOPO-based flame retardant in this paper. Then the flame retardant PA66 fiber was manufactured via melt spinning. The properties of flame retardant PA66 and flame retardant PA66 fiber were investigated by relative viscosity, differential scanning calorimetry (DSC), tensile test, vertical burning test (UL94) and limiting oxygen index (LOI) test. Although the loading of the DOPO-based flame retardant decreased the molecular weight, the melting temperature, the crystallinity and the mechanical properties of flame retardant PA66, the flame retardancy properties improved. The flame retardant PA66 loaded with 5.5 wt% of DOPO-based flame retardant can achieve a UL94 V-0 rating with a LOI value of 32.9%. The tenacity at break decreased from 4.51 cN·dtex-1 for PA66 fiber to 2.82 cN·dtex-1 for flame retardant PA66 fiber which still satisfied the requirements for fabrics. The flame retardant PA66 fiber expanded the application of PA66 materials which had a broad developing prospect.

  2. 30 CFR 56.6904 - Smoking and open flames.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Smoking and open flames. 56.6904 Section 56.6904 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL... Requirements § 56.6904 Smoking and open flames. Smoking and use of open flames shall not be permitted within...

  3. Entrainment regimes and flame characteristics of wildland fires

    Science.gov (United States)

    Ralph M. Nelson; Bret W. Butler; David R. Weise

    2012-01-01

    This paper reports results from a study of the flame characteristics of 22 wind-aided pine litter fires in a laboratory wind tunnel and 32 field fires in southern rough and litter-grass fuels. Flame characteristic and fire behaviour data from these fires, simple theoretical flame models and regression techniques are used to determine whether the data support the...

  4. Flame-Vortex Interactions Imaged in Microgravity - To Assess the Theory Flame Stretch

    Science.gov (United States)

    Driscoll, James F.

    2001-01-01

    The goals of this research are to: 1) Assess the Theory of Flame Stretch by operating a unique flame-vortex experiment under microgravity conditions in the NASA Glenn 2.2 Second Drop Tower (drops to identify operating conditions have been completed); 2) Obtain high speed shadowgraph images (500-1000 frames/s) using the drop rig (images were obtained at one-g, and the NASA Kodak RO camera is being mounted on the drop rig); 3) Obtain shadowgraph and PIV images at 1-g while varying the effects of buoyancy by controlling the Froude number (completed); 4) Numerically model the inwardly-propagating spherical flame that is observed in the experiment using full chemistry and the RUN 1DL code (completed); 5) Send images of the flame shape to Dr. G. Patniak at NRL who is numerically simulating the entire flame-vortex interaction of the present experiment (data transfer completed); and 6) Assess the feasibility of obtaining PIV velocity field images in the drop rig, which would be useful (but not required) for our assessment of the Theory of Flame Stretch (PIV images were obtained at one-g using same low laser power that is available from fiber optic cable in drop tower). The motivation for the work is to obtain novel measurement needed to develop a physically accurate model of turbulent combustion that can help in the control of engine pollutants. The unique experiment allows, for the first time, the detailed study of a negatively-curved (negatively stretched) flame, which is one of the five fundamental types of premixed flames. While there have been studies of flat flames, positively-curved (outwardly-propagating) cases and positively-strained (counterflow) cases, this is the first detailed study of a negatively-curved (inwardly-propagating) flame. The first set of drops in the 2.2 Second Drop Tower showed that microgravity provides more favorable conditions for achieving inwardly-propagating flames (IPFs) than 1-g. A vortex interacts with a flame and creates a spherical

  5. Computatonal and experimental study of laminar flames

    Energy Technology Data Exchange (ETDEWEB)

    Smooke, M.D.; Long, M.B. [Yale Univ., New Haven, CT (United States)

    1993-12-01

    This research has centered on an investigation of the effects of complex chemistry and detailed transport on the structure and extinction of hydrocarbon flames in counterflow, cylindrical and coflowing axisymmetric configurations. The authors have pursued both computational and experimental aspects of the research in parallel. The computational work has focused on the application of accurate and efficient numerical methods for the solution of the one and two-dimensional nonlinear boundary value problems describing the various reacting systems. Detailed experimental measurements were performed on axisymmetric coflow flames using two-dimensional imaging techniques. In particular, spontaneous Raman scattering and laser induced fluorescence were used to measure the temperature, major and minor species profiles.

  6. Pdf prediction of supersonic hydrogen flames

    Science.gov (United States)

    Eifler, P.; Kollmann, W.

    1993-01-01

    A hybrid method for the prediction of supersonic turbulent flows with combustion is developed consisting of a second order closure for the velocity field and a multi-scalar pdf method for the local thermodynamic state. It is shown that for non-premixed flames and chemical equilibrium mixture fraction, the logarithm of the (dimensionless) density, internal energy per unit mass and the divergence of the velocity have several advantages over other sets of scalars. The closure model is applied to a supersonic non-premixed flame burning hydrogen with air supplied by a supersonic coflow and the results are compared with a limited set of experimental data.

  7. Effect of Oxygen Enrichment in Propane Laminar Diffusion Flames under Microgravity and Earth Gravity Conditions

    Science.gov (United States)

    Bhatia, Pramod; Singh, Ravinder

    2017-01-01

    Diffusion flames are the most common type of flame which we see in our daily life such as candle flame and match-stick flame. Also, they are the most used flames in practical combustion system such as industrial burner (coal fired, gas fired or oil fired), diesel engines, gas turbines, and solid fuel rockets. In the present study, steady-state global chemistry calculations for 24 different flames were performed using an axisymmetric computational fluid dynamics code (UNICORN). Computation involved simulations of inverse and normal diffusion flames of propane in earth and microgravity condition with varying oxidizer compositions (21, 30, 50, 100 % O2, by mole, in N2). 2 cases were compared with the experimental result for validating the computational model. These flames were stabilized on a 5.5 mm diameter burner with 10 mm of burner length. The effect of oxygen enrichment and variation in gravity (earth gravity and microgravity) on shape and size of diffusion flames, flame temperature, flame velocity have been studied from the computational result obtained. Oxygen enrichment resulted in significant increase in flame temperature for both types of diffusion flames. Also, oxygen enrichment and gravity variation have significant effect on the flame configuration of normal diffusion flames in comparison with inverse diffusion flames. Microgravity normal diffusion flames are spherical in shape and much wider in comparison to earth gravity normal diffusion flames. In inverse diffusion flames, microgravity flames were wider than earth gravity flames. However, microgravity inverse flames were not spherical in shape.

  8. Effect of Oxygen Enrichment in Propane Laminar Diffusion Flames under Microgravity and Earth Gravity Conditions

    Science.gov (United States)

    Bhatia, Pramod; Singh, Ravinder

    2017-06-01

    Diffusion flames are the most common type of flame which we see in our daily life such as candle flame and match-stick flame. Also, they are the most used flames in practical combustion system such as industrial burner (coal fired, gas fired or oil fired), diesel engines, gas turbines, and solid fuel rockets. In the present study, steady-state global chemistry calculations for 24 different flames were performed using an axisymmetric computational fluid dynamics code (UNICORN). Computation involved simulations of inverse and normal diffusion flames of propane in earth and microgravity condition with varying oxidizer compositions (21, 30, 50, 100 % O2, by mole, in N2). 2 cases were compared with the experimental result for validating the computational model. These flames were stabilized on a 5.5 mm diameter burner with 10 mm of burner length. The effect of oxygen enrichment and variation in gravity (earth gravity and microgravity) on shape and size of diffusion flames, flame temperature, flame velocity have been studied from the computational result obtained. Oxygen enrichment resulted in significant increase in flame temperature for both types of diffusion flames. Also, oxygen enrichment and gravity variation have significant effect on the flame configuration of normal diffusion flames in comparison with inverse diffusion flames. Microgravity normal diffusion flames are spherical in shape and much wider in comparison to earth gravity normal diffusion flames. In inverse diffusion flames, microgravity flames were wider than earth gravity flames. However, microgravity inverse flames were not spherical in shape.

  9. Radiative Structures of Lycopodium-Air Flames in Low Gravity

    Science.gov (United States)

    Berlad, A. L.; Tangirala, V.; Ross, H.; Facca, L.

    1989-01-01

    Initially uniform clouds of fuel particulates in air sustain processes which may lead to particle cloud nonuniformities. In low gravity, flame-induced Kundt's Tube phenomena are observed to form regular patterns of nonuniform particle concentrations. Irregular patterns of particle concentrations also are observed to result from selected nonuniform mixing processes. Low gravity flame propagation for each of these classes of particle cloud flames has been found to depend importantly on the flame-generated infrared radiative fields. The spatial structures of these radiative fields are described. Application is made for the observed clases of lycopodium-air flames.

  10. FLARE FLAME INSTABILITY AND BURNER COMBUSTION CONTROL

    OpenAIRE

    БОНДАРЕНКО А.В.; В. Э. Волков; Максимов, М. В.

    2014-01-01

    Research of the flare instability development and the laminar-to-turbulent transition for the flares was executed. It was proved that the effects of viscosity and compressibility have the stabilizing influence on the gas flame. The study of the individual flare stability makes the theoretical basis of the fuel burning technology in combustion chambers and for the burner combustion control.

  11. Radical recombinations in acetylene-air flames

    NARCIS (Netherlands)

    Zeegers, P.J.Th.; Alkemade, C.T.J.

    1965-01-01

    In this paper an analysis is given of the behaviour of excess radical concentrations, H, OH and O as a function of height above the reaction zone in premixed acetylene-air flames at 2–200° to 2400°K and 1 atmosphere pressure. The intensity was measured of the Li resonance line which is related to th

  12. Numerical study of one swirling flame

    DEFF Research Database (Denmark)

    Yang, Yang; Kær, Søren Knudsen; Yin, Chungen

    This paper presents numerical study of one of Sydney swirl flames. Good agreements gained between numerical results and the experimental data. Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) methods show different flow patterns in isothermal and reacting case. The influence...

  13. Flame assisted synthesis of catalytic ceramic membranes

    DEFF Research Database (Denmark)

    Johansen, Johnny; Mosleh, Majid; Johannessen, Tue

    2004-01-01

    technology it is possible to make supported catalysts, composite metal oxides, catalytically active surfaces, and porous ceramic membranes. Membrane layers can be formed by using a porous substrate tube (or surface) as a nano-particle filter. The aerosol gas from the flame is led through a porous substrate...

  14. Experiments and modelling on vertical flame spread

    Energy Technology Data Exchange (ETDEWEB)

    Keski-Rahkonen, O.; Mangs, J. [VTT Building and Transport, Espoo (Finland)

    2004-07-01

    he principle and some preliminary results are shown of a new vertical flame spread modelling effort. Quick experimental screenings on relevant phenomena are made, some models are evaluated, and a new set of needed measuring instruments is proposed. Finally a single example of FRNC cable is shown as application of the methods. (orig.)

  15. Brominated flame retardants and endocrine disruption

    NARCIS (Netherlands)

    Vos, J.G.; Becher, G.; Berg, van den M.; Boer, de J.; Leonards, P.E.G.

    2003-01-01

    From an environmental point of view, an increasing important group of organohalogen compounds are the brominated flame retardants (BFRs), which are widely used in polymers and textiles and applied in construction materials, furniture, and electronic equipment. BFRs with the highest production volume

  16. Laminar Flame Speeds of Gasoline Surrogates Measured with the Flat Flame Method

    KAUST Repository

    Liao, Y.-H.

    2016-01-27

    © 2016 American Chemical Society. The adiabatic, laminar flame speeds of gasoline surrogates at atmospheric pressure over a range of equivalence ratios of = 0.8-1.3 and unburned gas temperatures of 298-400 K are measured with the flat flame method, which produces a one-dimensional flat flame free of stretch. Surrogates used in the current work are the primary reference fuels (PRFs, mixtures of n-heptane and isooctane), the toluene reference fuels (TRFs, mixtures of toluene and PRFs), and the ethanol reference fuels (ERFs, mixtures of ethanol and PRFs). In general, there is good agreement between the present work and the literature data for single-component fuel and PRF mixtures. Surrogates of TRF mixtures are found to exhibit comparable flame speeds to a real gasoline, while there is discrepancy observed between isooctane and gasoline. Moreover, the laminar flame speeds of TRF mixtures with similar fractions of n-heptane are found to be insensitive to the quantity of toluene in the mixture. Mixtures of ERFs exhibit comparable flame speeds to those of TRFs with similar mole fractions of n-heptane and isooctane.

  17. Radiation Heat Transfer in Particle-Laden Gaseous Flame: Flame Acceleration and Triggering Detonation

    CERN Document Server

    Liberman, M A; Kiverin, A D

    2015-01-01

    In this study we examine influence of the radiation heat transfer on the combustion regimes in the mixture, formed by suspension of fine inert particles in hydrogen gas. The gaseous phase is assumed to be transparent for the thermal radiation, while the radiant heat absorbed by the particles is then lost by conduction to the surrounding gas. The particles and gas ahead of the flame is assumed to be heated by radiation from the original flame. It is shown that the maximum temperature increase due to the radiation preheating becomes larger for a flame with lower velocity. For a flame with small enough velocity temperature of the radiation preheating may exceed the crossover temperature, so that the radiation heat transfer may become a dominant mechanism of the flame propagation. In the case of non-uniform distribution of particles, the temperature gradient formed due to the radiation preheating can initiate either deflagration or detonation ahead of the original flame via the Zel'dovich's gradient mechanism. Th...

  18. The flame anchoring mechanism and associated flow structure in bluff-body stabilized lean premixed flames

    Science.gov (United States)

    Michaels, Dan; Shanbhogue, Santosh; Ghoniem, Ahmed

    2015-11-01

    We present numerical analysis of a lean premixed flame anchoring on a heat conducting bluff-body. Different mixtures of CH4/H2/air are analyzed in order to systematically vary the burning velocity, adiabatic flame temperature and extinction strain rate. The study was motivated by our experimental measurements in a step combustor which showed that both the recirculation zone length and stability map under acoustically coupled conditions for different fuels and thermodynamic conditions collapse using the extinction strain rate. The model fully resolves unsteady two-dimensional flow with detailed chemistry and species transport, and without artificial flame anchoring boundary conditions. The model includes a low Mach number operator-split projection algorithm, coupled with a block-structured adaptive mesh refinement and an immersed boundary method for the solid body. Calculations reveal that the recirculation zone length correlates with the flame extinction strain rate, consistent with the experimental evidence. It is found that in the vicinity of the bluff body the flame is highly stretched and its leading edge location is controlled by the reactants combustion characteristics under high strain. Moreover, the flame surface location relative to the shear layer influences the vorticity thus impacting the velocity field and the recirculation zone. The study sheds light on the experimentally observed collapse of the combustor dynamics using the reactants extinction strain rate.

  19. Flame retardancy and its mechanism of polymers flame retarded by DBDPE/Sb2O3

    Institute of Scientific and Technical Information of China (English)

    ZUO Jian-dong; LI Rong-xun; FENG Shao-hua; LIU Guang-ye; ZHAO Jian-qing

    2008-01-01

    The flammability characterization and thermal composition of polymers flame retarded by decabromodiphenylethane(DBDPE) and antimony trioxide (Sb2O3) were studied by cone calorimeter and thermogravimetry (TG). The results show thatABS/DBDPE/Sb2O3 has the similar flammability parameters and thermal composition curves to ABS/DBDPO/Sb3O3. It suggests thatDBDPE/Sb2O3 has the similar flame retardant behavior to DBDPO/Sb2O3. The heat release rate (HRR) and the effect heat combustion (EHC) curves of polymers flame retarded by DBDPE/Sb2O3 all decrease, but the mass loss rate (MLR) curve slightly increase. It shows that the decrease of HRR is not due to the increase of char formation ratio but the generation of incombustible gases. The major flame retardant mechanism of DBDPE/Sb2O3 is gas phase flame retardant mechanism. Increasing content of Sb2O3in DBDPE/Sb2O3 can improve the flame retardant property and thermal stability of aerylonitrile butadiene styrene. Sb203 has a good synergistic effect with DBDPE.

  20. Numerical assessment of accurate measurements of laminar flame speed

    Science.gov (United States)

    Goulier, Joules; Bizon, Katarzyna; Chaumeix, Nabiha; Meynet, Nicolas; Continillo, Gaetano

    2016-12-01

    In combustion, the laminar flame speed constitutes an important parameter that reflects the chemistry of oxidation for a given fuel, along with its transport and thermal properties. Laminar flame speeds are used (i) in turbulent models used in CFD codes, and (ii) to validate detailed or reduced mechanisms, often derived from studies using ideal reactors and in diluted conditions as in jet stirred reactors and in shock tubes. End-users of such mechanisms need to have an assessment of their capability to predict the correct heat released by combustion in realistic conditions. In this view, the laminar flame speed constitutes a very convenient parameter, and it is then very important to have a good knowledge of the experimental errors involved with its determination. Stationary configurations (Bunsen burners, counter-flow flames, heat flux burners) or moving flames (tubes, spherical vessel, soap bubble) can be used. The spherical expanding flame configuration has recently become popular, since it can be used at high pressures and temperatures. With this method, the flame speed is not measured directly, but derived through the recording of the flame radius. The method used to process the radius history will have an impact on the estimated flame speed. Aim of this work is to propose a way to derive the laminar flame speed from experimental recording of expanding flames, and to assess the error magnitude.

  1. Laser-saturated fluorescence measurements in laminar sooting diffusion flames

    Science.gov (United States)

    Wey, Changlie

    1993-01-01

    The hydroxyl radical is known to be one of the most important intermediate species in the combustion processes. The hydroxyl radical has also been considered a dominant oxidizer of soot particles in flames. In this investigation the hydroxyl concentration profiles in sooting diffusion flames were measured by the laser-saturated fluorescence (LSF) method. The temperature distributions in the flames were measured by the two-line LSF technique and by thermocouple. In the sooting region the OH fluorescence was too weak to make accurate temperature measurements. The hydroxyl fluorescence profiles for all four flames presented herein show that the OH fluorescence intensities peaked near the flame front. The OH fluorescence intensity dropped sharply toward the dark region of the flame and continued declining to the sooting region. The OH fluorescence profiles also indicate that the OH fluorescence decreased with increasing height in the flames for all flames investigated. Varying the oxidizer composition resulted in a corresponding variation in the maximum OH concentration and the flame temperature. Furthermore, it appears that the maximum OH concentration for each flame increased with increasing flame temperature.

  2. Intracluster light properties in the CLASH-VLT cluster MACS J1206.2-0847

    Science.gov (United States)

    Presotto, V.; Girardi, M.; Nonino, M.; Mercurio, A.; Grillo, C.; Rosati, P.; Biviano, A.; Annunziatella, M.; Balestra, I.; Cui, W.; Sartoris, B.; Lemze, D.; Ascaso, B.; Moustakas, J.; Ford, H.; Fritz, A.; Czoske, O.; Ettori, S.; Kuchner, U.; Lombardi, M.; Maier, C.; Medezinski, E.; Molino, A.; Scodeggio, M.; Strazzullo, V.; Tozzi, P.; Ziegler, B.; Bartelmann, M.; Benitez, N.; Bradley, L.; Brescia, M.; Broadhurst, T.; Coe, D.; Donahue, M.; Gobat, R.; Graves, G.; Kelson, D.; Koekemoer, A.; Melchior, P.; Meneghetti, M.; Merten, J.; Moustakas, L. A.; Munari, E.; Postman, M.; Regős, E.; Seitz, S.; Umetsu, K.; Zheng, W.; Zitrin, A.

    2014-05-01

    Aims: We aim constrain the assembly history of clusters by studying the intracluster light (ICL) properties, estimating its contribution to the fraction of baryons in stars, f∗, and understanding possible systematics or bias using different ICL detection techniques. Methods: We developed an automated method, GALtoICL, based on the software GALAPAGOS, to obtain a refined version of typical BCG+ICL maps. We applied this method to our test case MACS J1206.2-0847, a massive cluster located at z ~ 0.44, which is part of the CLASH sample. Using deep multiband Subaru images, we extracted the surface brightness (SB) profile of the BCG+ICL and studied the ICL morphology, color, and contribution to f∗ out to R500. We repeated the same analysis using a different definition of the ICL, SBlimit method, i.e., a SB cut-off level, to compare the results. Results: The most peculiar feature of the ICL in MACS1206 is its asymmetric radial distribution, with an excess in the SE direction and extending toward the second brightest cluster galaxy, which is a post starburst galaxy. This suggests an interaction between the BCG and this galaxy that dates back to τ ≤ 1.5 Gyr. The BCG+ICL stellar content is ~8% of M∗,500, and the (de-) projected baryon fraction in stars is f∗ = 0.0177(0.0116), in excellent agreement with recent results. The SBlimit method provides systematically higher ICL fractions and this effect is stronger at lower SB limits. This is due to the light from the outer envelopes of member galaxies that contaminate the ICL. Though more time consuming, the GALtoICL method provides safer ICL detections that are almost free of this contamination. This is one of the few ICL study at redshift z > 0.3. At completion, the CLASH/VLT program will allow us to extend this analysis to a statistically significant cluster sample spanning a wide redshift range: 0.2 ≲ z ≲ 0.6. Based on data collected at the NASJ Subaru telescope, at the ESO VLT (prog.ID 186.A-0798), and the

  3. The OmegaCAM 16K x 16K CCD detector system for the ESO VLT Survey Telescope (VST)

    NARCIS (Netherlands)

    Iwert, Olaf; Baade, D.; Balestra, A.; Baruffolo, A.; Bortolussi, A.; Christen, F.; Cumani, C.; Deiries, S.; Downing, M.; Geimer, C.; Hess, G.; Hess, J.; Kuijken, K.; Lizon, J.; Muschielok, B.; Nicklas, H.; Reiss, R.; Reyes, J.; Silber, A.; Thillerup, J.; Valentijn, E.; Dorn, David A.; Holland, Andrew D.

    2006-01-01

    A 16K x 16K, 1 degree x 1 degree field, detector system was developed by ESO for the OmegaCAM instrument for use on the purpose built ESO VLT Survey Telescope (VST). The focal plane consists of an 8 x 4 mosaic of 2K x 4K 15um pixel e2v CCDs and four 2K x 4K CCDs on the periphery for the opto-mechani

  4. Modeling and simulation of axisymmetric stagnation flames

    Science.gov (United States)

    Sone, Kazuo

    Laminar flame modeling is an important element in turbulent combustion research. The accuracy of a turbulent combustion model is highly dependent upon our understanding of laminar flames and their behavior in many situations. How much we understand combustion can only be measured by how well the model describes and predicts combustion phenomena. One of the most commonly used methane combustion models is GRI-Mech 3.0. However, how well the model describes the reacting flow phenomena is still uncertain even after many attempts to validate the model or quantify uncertainties. In the present study, the behavior of laminar flames under different aerodynamic and thermodynamic conditions is studied numerically in a stagnation-flow configuration. In order to make such a numerical study possible, the spectral element method is reformulated to accommodate the large density variations in methane reacting flows. In addition, a new axisymmetric basis function set for the spectral element method that satisfies the correct behavior near the axis is developed, and efficient integration techniques are developed to accurately model axisymmetric reacting flow within a reasonable amount of computational time. The numerical method is implemented using an object-oriented programming technique, and the resulting computer program is verified with several different verification methods. The present study then shows variances with the commonly used GRI-Mech 3.0 chemical kinetics model through a direct simulation of laboratory flames that allows direct comparison to experimental data. It is shown that the methane combustion model based on GRI-Mech 3.0 works well for methane-air mixtures near stoichiometry. However, GRI-Mech 3.0 leads to an overprediction of laminar flame speed for lean mixtures and an underprediction for rich mixtures. This result is slightly different from conclusion drawn in previous work, in which experimental data are compared with a one-dimensional numerical solutions

  5. Leading-Edge Velocities and Lifted Methane Jet Flame Stability

    Directory of Open Access Journals (Sweden)

    W. Wang

    2010-01-01

    Full Text Available Current interest exists in understanding reaction-zone dynamics and mechanisms with respect to how they counterpropagate against incoming reactants. Images of flame position and flow-field morphology are presented from flame chemiluminescence and particle image velocimetry (PIV measurements. In the present study, PIV experiments were carried out to measure the methane jet lifted-flame flow-field velocities in the vicinity of the flame leading edge. Specifically, velocity fields within the high-temperature zone were examined in detail, which complements previous studies, whose prime focus is the flow-field upstream of the high-temperature boundary. PIV data is used not only to determine the velocities, but, along with chemiluminescence images, to also indicate the approximate location of the reaction zone (further supported by/through the leading-edge flame velocity distributions. The velocity results indirectly support the concept that the flame is anchored primarily through the mechanism of partially premixed flame propagation.

  6. Flame quenching process in cavity based on model scramjet combustor

    Institute of Scientific and Technical Information of China (English)

    Yu Pan; Jing Lei; Jian-Han Liang; Wei-Dong Liu; Zhen-Guo Wang

    2012-01-01

    The flame quenching process in combustors was observed by high speed camera and Schlieren system,at the inflow conditions of Ma =2.64,To =1 483 K,P0 =1.65 MPa,T =724 K and P =76.3 kPa.Changing process of the flame and shock structure in the combustor was clearly observed.The results revealed that the precombustion shock disappeared accompanied with the process in which the flame was blown out and withdrawed from the mainflow into the cavity and vanished after a short while.The rime of quenching process was extended by the cavity flame holder,and the ability of flame holding was enhanced by arranging more cavities in the downstream as well.The flame was blown from the upstream to the downstream,so the flame in the downstream of the cavity was quenched out later than that in the upstream.

  7. Flame Propagation of Butanol Isomers/Air Mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Veloo, Peter S.; Egolfopoulos, Fokion N.

    2011-01-01

    An experimental and computational study was conducted on the propagation of flames of saturated butanol isomers. The experiments were performed in the counterflow configuration under atmospheric pressure, unburned mixture temperature of 343 K, and for a wide range of equivalence ratios. The experiments were simulated using a recent kinetic model for the four isomers of butanol. Results indicate that n-butanol/air flames propagate somewhat faster than both sec-butanol/air and iso-butanol/air flames, and that tert-butanol/air flames propagate notably slower compared to the other three isomers. Reaction path analysis of tert-butanol/air flames revealed that iso-butene is a major intermediate, which subsequently reacts to form the resonantly stable iso-butenyl radical retarding thus the overall reactivity of tert-butanol/air flames relatively to the other three isomers. Through sensitivity analysis, it was determined that the mass burning rates of sec-butanol/air and iso-butanol/air flames are sensitive largely to hydrogen, carbon monoxide, and C{sub 1}–C{sub 2} hydrocarbon kinetics and not to fuel-specific reactions similarly to n-butanol/air flames. However, for tert-butanol/air flames notable sensitivity to fuel-specific reactions exists. While the numerical results predicted closely the experimental data for n-butanol/air and sec-butanol/air flames, they overpredicted and underpredicted the laminar flame speeds for iso-butanol/air and tert-butanol/air flames respectively. It was demonstrated further that the underprediction of the laminar flame speeds of tert-butanol/air flames by the model was most likely due to deficiencies of the C{sub 4}-alkene kinetics.

  8. Shapes of Buoyant and Nonbuoyant Methane Laminar Jet Diffusion Flames

    Science.gov (United States)

    Sunderland, Peter B.; Yuan, Zeng-Guang; Urban, David L.

    1997-01-01

    Laminar gas jet diffusion flames represent a fundamental combustion configuration. Their study has contributed to numerous advances in combustion, including the development of analytical and computational combustion tools. Laminar jet flames are pertinent also to turbulent flames by use of the laminar flamelet concept. Investigations into the shapes of noncoflowing microgravity laminar jet diffusion flames have primarily been pursued in the NASA Lewis 2.2-second drop tower, by Cochran and coworkers and by Bahadori and coworkers. These studies were generally conducted at atmospheric pressure; they involved soot-containing flames and reported luminosity lengths and widths instead of the flame-sheet dimensions which are of Greater value to theory evaluation and development. The seminal model of laminar diffusion flames is that of Burke and Schumann, who solved the conservation of momentum equation for a jet flame in a coflowing ambient by assuming the velocity of fuel, oxidizer and products to be constant throughout. Roper and coworkers improved upon this model by allowing for axial variations of velocity and found flame shape to be independent of coflow velocity. Roper's suggestion that flame height should be independent of gravity level is not supported by past or present observations. Other models have been presented by Klajn and Oppenheim, Markstein and De Ris, Villermaux and Durox, and Li et al. The common result of all these models (except in the buoyant regime) is that flame height is proportional to fuel mass flowrate, with flame width proving much more difficult to predict. Most existing flame models have been compared with shapes of flames containing soot, which is known to obscure the weak blue emission of flame sheets. The present work involves measurements of laminar gas jet diffusion flame shapes. Flame images have been obtained for buoyant and nonbuoyant methane flames burning in quiescent air at various fuel flow-rates, burner diameters and ambient

  9. Behaviors of tribrachial edge flames and their interactions in a triple-port burner

    KAUST Repository

    Yamamoto, Kazuhiro

    2015-05-01

    In a triple-port burner, various non-premixed flames have been observed previously. Especially for the case with two lifted flames, such configuration could be suitable in studying interaction between two tribrachial flames. In the present study, the flame characteristics have been investigated numerically by adopting a reduced kinetic mechanism in the triple-port burner. Four different types of flame configurations, including two attached flames, inner lifted/outer attached flames, inner attached/outer lifted flames, and twin lifted flames, were successfully simulated depending on the flow conditions. The representative edge propagation speed of a single lifted flame or an upstream lifted flame in the case of twin lifted flames increased as the liftoff height became higher. In the twin lifted flames, the inner lifted flame was affected appreciably when the other flame was located further upstream such that the lifted flame located further downstream encountered the axial velocity acceleration induced by the gas expansion from the lifted flame located upstream, while thermal effects were not observed since the temperature of the incoming flow toward the lifted flame was not affected. A unique flip-flop behavior between the inner and outer flames, observed experimentally previously, was successfully captured in the simulation such that the inner lifted flame became attached to the nozzle as the liftoff height of the outer lifted flame grew higher with an increase in the outer air velocity.

  10. Status and new operation modes of the versatile VLT/NaCo

    Science.gov (United States)

    Girard, Julien H. V.; Kasper, Markus; Quanz, Sascha P.; Kenworthy, Matthew A.; Rengaswamy, Sridharan; Schödel, Rainer; Gallenne, Alexandre; Gillessen, Stefan; Huerta, Nicolas; Kervella, Pierre; Kornweibel, Nick; Lenzen, Rainer; Mérand, Antoine; Montagnier, Guillaume; O'Neal, Jared; Zins, Gérard

    2010-07-01

    This paper aims at giving an update on the most versatile Adaptive Optics fed instrument to date, the well known and successful NACO*. Although NACO is only scheduled for about two more years† at the Very Large Telescope (VLT), it keeps on evolving with additional operation modes bringing original astronomical results. The high contrast imaging community uses it creatively as a test-bench for SPHERE‡ and other second generation planet imagers. A new visible wavefront sensor (WFS) optimized for Laser Guide Star (LGS) operations has been installed and tested, the cube mode is more and more required for frame selection on bright sources, a seeing enhancer mode (no tip/tilt correction) is now offered to provide full sky coverage and welcome all kind of extragalactic applications, etc. The Instrument Operations Team (IOT) and Paranal engineers are currently working hard at maintaining the instrument overall performances but also at improving them and offering new capabilities, providing the community with a well tuned and original instrument for the remaining time it is being used. The present contribution delivers a non-exhaustive overview of the new modes and experiments that have been carried out in the past months.

  11. VLT/SPHERE deep insight of NGC 3603's core: Segregation or confusion?

    CERN Document Server

    Khorrami, Z; Vakili, F; Lagadec, E; Langlois, M; Brandner, W; Chesneau, O; Meyer, M R; Carbillet, M; Abe, L; Mouillet, D; Beuzit, JL; Boccaletti, A; Perrot, C; Thalmann, C; Schmid, H -M; Pavlov, A; Costille, A; Dohlen, K; Mignant, D Le; Petit, C; Sauvage, J F

    2016-01-01

    We present new near-infrared photometric measurements of the core of the young massive cluster NGC 3603 obtained with extreme adaptive optics. The data were obtained with the SPHERE instrument mounted on ESO Very Large Telescope, and cover three fields in the core of this cluster. We applied a correction for the effect of extinction to our data obtained in the J and K broadband filters and estimated the mass of detected sources inside the field of view of SPHERE/IRDIS, which is 13.5"x13.5". We derived the mass function (MF) slope for each spectral band and field. The MF slope in the core is unusual compared to previous results based on Hubble space telescope (HST) and very large telescope (VLT) observations. The average slope in the core is estimated as -1.06^{+0.26}_{-0.26} for the main sequence stars with 3.5 Msun < M < 120 Msun.Thanks to the SPHERE extreme adaptive optics, 814 low-mass stars were detected to estimate the MF slope for the pre-main sequence stars with 0.6 Msun< M < 3.5 Msun , Gam...

  12. Spectral analysis of Uranus' 2014 bright storm with VLT/SINFONI

    CERN Document Server

    Irwin, Patrick G J; Read, Peter L; Tice, Dane; de Pater, Imke; Orton, Glenn S; Teanby, Nicholas A; Davis, Gary R

    2015-01-01

    An extremely bright storm system observed in Uranus' atmosphere by amateur observers in September 2014 triggered an international campaign to observe this feature with many telescopes across the world. Observations of the storm system in the near infrared were acquired in October and November 2014 with SINFONI on ESO's Very Large Telescope (VLT) in Chile. SINFONI is an Integral Field Unit spectrometer returning 64x64 pixel images with 2048 wavelengths. Image cubes in the H-band (1.43 - 1.87 microns) were obtained at spatial resolutions of ~0.1". The observations show that the centre of the storm feature shifts markedly with increasing altitude, moving in the retrograde direction and slightly poleward with increasing altitude. We also see a faint 'tail' of more reflective material to the immediate south of the storm, which again trails in the retrograde direction. The observed spectra were analysed with the radiative transfer and retrieval code, NEMESIS. We find that the storm is well-modelled using either two...

  13. The VLT LBG Redshift Survey - IV. Gas and galaxies at z~3 in observations and simulations

    CERN Document Server

    Tummuangpak, P; Bielby, R; Crighton, N H M; Francke, H; Infante, L; Theuns, T

    2013-01-01

    We use observations and simulations to study the relationship between star-forming galaxies and the IGM at z~3. We use redshift data taken from the VLT LBG Redshift Survey (VLRS) and Keck surveys in fields centred on bright background QSOs, whilst the simulated data is taken from GIMIC. In the simulations, we find that the dominant peculiar velocities are in the form of large-scale coherent motions of gas and galaxies. Gravitational infall of galaxies towards each other is also seen, consistent with linear theory. Peculiar velocity pairs with separations smaller than 1Mpc have a smaller dispersion and better explain the simulated z-space correlations. Lyman-alpha auto- and cross-correlations in the simulations appear to show smaller infall than implied by the expected beta_Lyman-alpha ~ 1.3. Galaxy-wide outflows implemented in the simulations may contribute to this effect. When velocity errors are taken into account, the LBG correlation function prefers the high clustering amplitude shown by higher mass galax...

  14. The VLT LBG Redshift Survey - V. Characterising the z = 3.1 Lyman Alpha Emitter Population

    CERN Document Server

    Bielby, R M; Shanks, T; Francke, H; Crighton, N H M; Bañados, E; González-López, Jorge; Infante, L; Orsi, A

    2016-01-01

    We present a survey of Ly$\\alpha$ emitting galaxies in the fields of the VLT LBG Redshift Survey, incorporating the analysis of narrow band number counts, the rest frame UV luminosity function and the two-point correlation function of Ly$\\alpha$ emitters at $z\\approx3.1$. Our photometric sample consists of 750 LAE candidates, over an area of 1.07 deg$^2$, with estimated equivalent widths of $\\gtrsim65$ \\AA, from 5 fields based on deep Subaru Suprime-Cam imaging data. Added to this we have obtained spectroscopic follow-up observations, which successfully detected Ly$\\alpha$ emission in 35 galaxies. Based on the spectroscopic results, we refined our photometric selection constraints, with the resulting sample having a success rate of $78\\pm18\\%$. We calculate the narrow band number counts for our photometric sample and find these to be consistent with previous studies of LAEs at this redshift. We find the $R$-band continuum luminosity function to be $\\sim10\\times$ lower than the equivalent luminosity function o...

  15. VLT Suzaku observations of the Fermi pulsar PSR J1028-5819

    CERN Document Server

    Mignani, R P; Esposito, P; De Luca, A; Marelli, M; Oates, S R; Saz-Parkinson, P

    2012-01-01

    We used optical images taken with the Very Large Telescope (VLT) in the B and V bands to search for the optical counterpart of PSR J1028-5819 or constrain its optical brightness. At the same time, we used an archival Suzaku observation to confirm the preliminary identification of the pulsar's X-ray counterpart obtained by Swift. Due to the large uncertainty on the pulsar's radio position and the presence of a bright (V = 13.2) early F-type star at < 4", we could not detect its counterpart down to flux limits of B~25.4 and V ~25.3, the deepest obtained so far for PSR J1028-5819. From the Suzaku observations, we found that the X-ray spectrum of the pulsar's candidate counterpart is best-fit by a power-law with spectral index 1.7 +/- 0.2 and an absorption column density NH < 10^21 cm-2, which would support the proposed X-ray identification. Moreover, we found possible evidence for the presence of diffuse emission around the pulsar. If real, and associated with a pulsar wind nebula (PWN), its surface bright...

  16. Discovery of a z = 6.17 galaxy from CFHT and VLT observations

    CERN Document Server

    Cuby, J G; McCracken, H; Cuillandre, J C; Magnier, E; Meneux, B

    2003-01-01

    We report the discovery of a galaxy at a redshift z = 6.17 identified from deep narrow band imaging and spectroscopic follow-up in one of the CFHT-VIRMOS deep survey fields at 0226-04. In addition to the existing deep BVRI images of this field, we obtained a very deep narrow band image at 920 nm with the aim of detecting Ly alpha emission at redshift ~ 6.5. Spectroscopic follow-up of some of the candidates selected on the basis of their excess flux in the NB920 filter was performed at the VLT-UT4 with the FORS2 instrument. For one object a strong and asymmetric emission line associated with a strong break in continuum emission is identified as Ly alpha at z = 6.17. This galaxy was selected from its continuum emission in the 920 nm filter rather than for its Ly alpha emission, in effect performing a Lyman Break detection at z = 6.17. We estimate a star formation rate of ~ 10 M/yr for this object, with a velocity dispersion \\~ 400 km/s. Similarly to other objects at redshifts ~ 5--6, this galaxy presents the ch...

  17. VLT\\/UVES Abundances in Four Nearby Dwarf Spheroidal Galaxies I. Nucleosynthesis and Abundance Ratios

    CERN Document Server

    Shetrone, M; Tolstoy, E; Primas, F; Hill, V; Kaufer, A

    2003-01-01

    We have used UVES on VLT-UT2 to take spectra of 15 red giants in the Sculptor, Fornax, Carina and Leo I dwarf spheroidal galaxies. We measure the abundances of alpha, iron peak, s and r-process elements. No dSph giants in our sample show the deep mixing abundance pattern seen in nearly all globular clusters. At a given metallicity, the dSph giants exhibit lower [el/Fe] abundance ratios for the alpha elements than stars in the Galactic halo. This can be caused by a slow star formation rate and contribution from Type Ia SN, and/or a small star formation event (low total mass) and mass dependent Type II SN yields. Differences in the even-Z [el/Fe] ratios between these galaxies, as well as differences in the evolution of the s&r-process elements are interpreted in terms of their star formation histories. Comparison of the dSph abundances with those of the Galactic halo reveals some consistencies. In particular, we find stars that mimic the abundance pattern found by Nissen & Shuster (1997) for metal-rich,...

  18. VLT/MUSE discovers a jet from the evolved B[e] star MWC 137

    CERN Document Server

    Mehner, A; Groh, J H; Oudmaijer, R D; Baade, D; Rivinius, T; Selman, F; Boffin, H M J; Martayan, C

    2016-01-01

    Not all stars exhibiting the optical spectral characteristics of B[e] stars share the same evolutionary stage. The Galactic B[e] star MWC 137 is a prime example of an object with uncertain classification, with previous work suggesting pre- and post-main sequence classification. Our goal is to settle this debate and provide reliable evolutionary classification. Integral field spectrograph observations with VLT MUSE of the cluster SH 2-266 are used to analyze the nature of MWC 137. A collimated outflow is discovered that is geometrically centered on MWC 137. The central position of MWC 137 in the cluster SH 2-266 within the larger nebula suggests strongly that it is a member of this cluster and that it is both at the origin of the nebula and the newly discovered jet. Comparison of the color-magnitude diagram of the brightest cluster stars with stellar evolutionary models results in a distance of about 5.2$\\pm$1.4 kpc. We estimate that the cluster is at least 3 Myr old. The jet extends over 66" (1.7 pc) projecte...

  19. VLT Phase Resolved Optical Spectroscopy of the Ultra-Compact Binary HM Cnc

    CERN Document Server

    Mason, Elena; Dall'Osso, S; Stella, L; Munari, U; Marconi, G; O'Brian, K; Covino, S; Fugazza, D

    2010-01-01

    A 321.5 s modulation was discovered in 1999 in the X-ray light curve of HM Cnc. In 2001 and 2002, optical photometric and spectroscopic observations revealed that HM Cnc is a very blue object with no intrinsic absorptions but broad (FWHM 1500 km s^-1) low equivalent width emission lines (EW 1-6A), which were first identified with the HeII Pickering series. The combination of X-ray and optical observations pictures HM Cnc as a double degenerate binary hosting two white dwarfs, and possibly being the shortest orbital period binary discovered so far. The present work is aimed at studying the orbital motion of the two components by following the variations of the shape, centroid and intensity of the emission lines through the orbit. In February 2007, we carried out the first phase resolved optical spectroscopic study with the VLT/FORS2 in the High Time Resolution (HIT) mode, yielding five phase bins in the 321 s modulation. Despite the low SNR, the data show that the intensity of the three most prominent emission...

  20. VLT Observations of Turnoff stars in the Globular Cluster NGC 6397

    CERN Document Server

    Thévenin, F; De Pacheco, J A F; Idiart, T P; Jasniewicz, G; De Laverny, P; Plez, B

    2001-01-01

    VLT-UVES high resolution spectra of seven turnoff stars in the metal-poor globular cluster NGC 6397 have been obtained. Atmospheric parameters and abundances of several elements (Li, Na, Mg, Ca, Sc, Ti, Cr, Fe, Ni, Zn and Ba) were derived for program stars. The mean iron abundance is [Fe/H] = -2.02, with no star-to-star variation. The mean abundances of the alpha-elements (Ca, Ti) and of the iron-peak elements (Sc, Cr, Ni) are consistent with abundances derived for field stars of similar metallicity. Magnesium is also almost solar, consistent with the values found by Idiart & Th\\'evenin (2000) when non-LTE effects (NLTE hereafter) are taken into account. The sodium abundance derived for five stars is essentially solar, but one object (A447) is clearly Na deficient. These results are compatible with the expected abundance range estimated from the stochastic evolutionary halo model by Argast et al. (2000) when at the epoch of [Fe/H] $\\sim$ -2 the interstellar medium is supposed to become well-mixed.

  1. Meridional variation in tropospheric methane on Titan observed with AO spectroscopy at Keck and VLT

    CERN Document Server

    Ádámkovics, Máté; Hayes, Alexander G; Rojo, Patricio M; Corlies, Paul; Barnes, Jason W; Ivanov, Valentin D; Brown, Robert H; Baines, Kevin H; Buratti, Bonnie J; Clark, Roger N; Nicholson, Philip D; Sotin, Christophe

    2015-01-01

    The spatial distribution of the tropospheric methane on Titan was measured using near-infrared spectroscopy. Ground-based observations at 1.5$\\mu{\\rm m}$ (H-band) were performed during the same night using instruments with adaptive optics at both the W. M. Keck Observatory and at the Paranal Observatory on 17 July 2014 UT. The integral field observations with SINFONI on the VLT covered the entire H-band at moderate resolving power, $R=\\lambda/\\Delta\\lambda\\approx1,500$, while the Keck observations were performed with NIRSPAO near 1.55254$\\mu{\\rm m}$ at higher resolution, $R\\approx25,000$. The moderate resolution observations are used for flux calibration and for the determination of model parameters that can be degenerate in the interpretation of high resolution spectra. Line-by-line calculations of CH$_4$ and CH$_3$D correlated $k$ distributions from the HITRAN 2012 database were used, which incorporate revised line assignments near 1.5$\\mu{\\rm m}$. We fit the surface albedo and aerosol distributions in the ...

  2. Spectroscopic confirmation of high-redshift supernovae with the ESO VLT

    CERN Document Server

    Lidman, C E; Folatelli, G; Garavini, G; Nobili, S; Aldering, G; Amanullah, R; Antilogus, P; Astier, Pierre; Blanc, G; Burns, M S; Conley, A; Deustua, S E; Doi, M; Ellis, R; Fabbro, S; Fadeev, V; Gibbons, R; Goldhaber, G; Goobar, A; Groom, D E; Hook, I; Kashikawa, N; Kim, A G; Knop, R A; Lee Byung Cheol; Méndez, J; Morokuma, T; Motohara, K; Nugent, P; Pain, R; Perlmutter, S; Prasad, V; Quimby, R; Raux, J; Regnault, N; Ruiz-Lapuente, P; Sainton, G; Schaefer, B E; Schahmaneche, K; Smith, E; Spadafora, A L; Stanishev, V; Walton, N A; Wang, L; Wood-Vasey, W M; Yasuda, N

    2004-01-01

    We present VLT FORS1 and FORS2 spectra of 39 candidate high-redshift supernovae that were discovered as part of a cosmological study using Type Ia supernovae (SNe Ia) over a wide range of redshifts. From the spectra alone, 20 candidates are spectrally classified as SNe Ia with redshifts ranging from z=0.212 to z=1.181. Of the remaining 19 candidates, 1 might be a Type II supernova and 11 exhibit broad supernova-like spectral features and/or have supernova-like light curves. The candidates were discovered in 8 separate ground-based searches. In those searches in which SNe Ia at z ~ 0.5 were targeted, over 80% of the observed candidates were spectrally classified as SNe Ia. In those searches in which SNe Ia with z > 1 were targeted, 4 candidates with z > 1 were spectrally classified as SNe Ia and later followed with ground and space based observatories. We present the spectra of all candidates, including those that could not be spectrally classified as supernova.

  3. Upper limits for mass and radius of objects around Proxima Cen from SPHERE/VLT

    Science.gov (United States)

    Mesa, D.; Zurlo, A.; Milli, J.; Gratton, R.; Desidera, S.; Langlois, M.; Vigan, A.; Bonavita, M.; Antichi, J.; Avenhaus, H.; Baruffolo, A.; Biller, B.; Boccaletti, A.; Bruno, P.; Cascone, E.; Chauvin, G.; Claudi, R. U.; De Caprio, V.; Fantinel, D.; Farisato, G.; Girard, J.; Giro, E.; Hagelberg, J.; Incorvaia, S.; Janson, M.; Kral, Q.; Lagadec, E.; Lagrange, A.-M.; Lessio, L.; Meyer, M.; Peretti, S.; Perrot, C.; Salasnich, B.; Schlieder, J.; Schmid, H.-M.; Scuderi, S.; Sissa, E.; Thalmann, C.; Turatto, M.

    2017-03-01

    The recent discovery of an earth-like planet around Proxima Centauri has drawn much attention to this star and its environment. We performed a series of observations of Proxima Centauri using Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE), the planet-finder instrument installed at the European Southern Observatory (ESO) Very Large Telescope (VLT) UT3, using its near-infrared modules, InfraRed Dual-band Imager and Spectrograph (IRDIS) and IFS. No planet was detected directly, but we set upper limits on the mass up to 7 au by exploiting the AMES-COND models. Our IFS observations reveal that no planet more massive than ∼6-7 MJup can be present within 1 au. The dual-band imaging camera IRDIS also enables us to probe larger separations than other techniques such as radial velocity or astrometry. We obtained mass limits of the order of 4 MJup at separations of 2 au or larger, representing the most stringent mass limits at separations larger than 5 au available at the moment. We also made an attempt to estimate the radius of possible planets around Proxima using the reflected light. Since the residual noise for the observations is dominated by photon noise and thermal background, longer exposures in good observing conditions could improve the achievable contrast limit further.

  4. VLT/VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies: 2D kinematic properties

    CERN Document Server

    Bellocchi, Enrica; Colina, Luis; Miralles-Caballero, Daniel

    2013-01-01

    We present and discuss the 2D kinematic properties of the ionized gas (Halpha) in a sample of 38 local (ultra) luminous infrared galaxies [(U)LIRGs] (31 LIRGs and 7 ULIRGs) observed with VIMOS at the VLT using integral field spectroscopy. This sample covers well the less studied LIRG luminosity range and includes isolated disks, interacting systems, and mergers. The majority of the galaxies have two main kinematically distinct components. One component (i.e., narrow or systemic) extends over the whole line-emitting region and is characterized by small to intermediate velocity dispersions (i.e., sigma from 30 to 160 km s^-1). It traces the overall velocity field. The second component (broad) has in general a larger velocity dispersion (up to 320 km s^-1), mainly found in the inner regions and generally blueshifted with respect to the systemic component. Most of the objects (76%) are dominated by rotation, more relevant in LIRGs than in ULIRGs. Isolated disks, interacting galaxies, and merging systems define a ...

  5. Design of a Full-Stokes Polarimeter for VLT/X-shooter

    CERN Document Server

    Snik, Frans; Navarro, Ramon; Groot, Paul; Kaper, Lex; de Wijn, Alfred

    2012-01-01

    X-shooter is one of the most popular instruments at the VLT, offering instantaneous spectroscopy from 300 to 2500 nm. We present the design of a single polarimetric unit at the polarization-free Cassegrain focus that serves all three spectrograph arms of X-shooter. It consists of a calcite Savart plate as a polarizing beam-splitter and a rotatable crystal retarder stack as a "polychromatic modulator". Since even "superachromatic" wave plates have a wavelength range that is too limited for X-shooter, this novel modulator is designed to offer close-to-optimal polarimetric efficiencies for all Stokes parameters at all wavelengths. We analyze the modulator design in terms of its polarimetric performance, its temperature sensitivity, and its polarized fringes. Furthermore, we present the optical design of the polarimetric unit. The X-shooter polarimeter will furnish a myriad of science cases: from measuring stellar magnetic fields (e.g., Ap stars, white dwarfs, massive stars) to determining asymmetric structures a...

  6. Testing intermediate-age stellar evolution models with VLT photometry of LMC clusters. I. The data

    CERN Document Server

    Gallart, C; Bertelli, G; Chiosi, C; Demarque, P; Girardi, L; Nasi, E; Woo, J H; Yi, S

    2003-01-01

    This is the first of a series of three papers devoted to the calibration of a few parameters of crucial importance in the modeling of the evolution of intermediate-mass stars, with special attention to the amount of convective core overshoot. To this end we acquired deep V and R photometry for three globular clusters of the Large Magellanic Cloud (LMC), namely NGC 2173, SL 556 and NGC 2155, in the age interval 1-3 Gyr. In this first paper, we describe the aim of the project, the VLT observations and data reduction, and we make preliminary comparisons of the color-magnitude diagrams with both Padova and Yonsei-Yale isochrones. Two following papers in this series present the results of a detailed analysis of these data, independently carried out by members of the Yale and Padova stellar evolution groups. This allows us to compare both sets of models and discuss their main differences, as well as the systematic effects that they would have to the determination of the ages and metallicities of intermediate-age si...

  7. A nearby GRB host galaxy: VLT/X-shooter observations of HG 031203

    CERN Document Server

    Guseva, N G; Fricke, K J; Henkel, C; 10.1051/0004-6361/201116765

    2011-01-01

    (abridged) Long-duration gamma-ray bursts (LGRBs) occur in galaxies of generally low metallicity. We aim at a spectroscopic analysis of HG 031203, the host galaxy of a LRGB burst, to obtain its properties. Based on VLT/X-shooter spectroscopic observations in the wavelength range 3200-24000A, we use standard direct methods to evaluate physical conditions and element abundances. The resolving power of the instrument also allowed us to trace the kinematics of the ionised gas. We derive an interstellar oxygen abundance of 12+logO/H=8.20+/-0.03. The observed fluxes of hydrogen lines correspond to the theoretical recombination values after correction for extinction with a single value C(Hbeta)=1.67. We produce the CLOUDY photoionisation HII region model that reproduces observed emission-line fluxes of different ions in the optical range. This model also predicts emission-line fluxes in the near-infrared (NIR) and mid-infrared (MIR) ranges that agree well with the observed ones. This implies that the star-forming re...

  8. Mid-infrared imaging of 25 local AGN with VLT-VISIR

    CERN Document Server

    Horst, Hannes; Gandhi, Poshak; Smette, Alain

    2009-01-01

    Aims. High angular resolution N-band imaging is used to discern the torus of active galactic nuclei (AGN) from its environment in order to allow a comparison of its mid-infrared properties to the expectations of the unified scenario for AGN. Methods. We present VLT-VISIR images of 25 low-redshift AGN of different Seyfert types, as well as N-band SEDs of 20 of them. In addition, we compare our results for 19 of them to Spitzer IRS spectra. Results. We find that at a resolution of ~ 0.35", all the nuclei of our observed sources are point-like, except for 2 objects whose extension is likely of instrumental origin. For 3 objects, however, we observed additional extended circumnuclear emission, even though our observational strategy was not designed to detect it. Comparison of the VISIR photometry and Spitzer spectrophotometry indicates that the latter is affected by extended emission in at least 7 out of 19 objects and the level of contamination is (0.20 ~ 0.85) * F_IRS. In particular, the 10 um silicate emission...

  9. CLASH-VLT: Testing the Nature of Gravity with Galaxy Cluster Mass Profiles

    CERN Document Server

    Pizzuti, L; Borgani, S; Amendola, L; Umetsu, K; Biviano, A; Girardi, M; Rosati, P; Balestra, I; Caminha, G B; Frye, B; Koekemoer, A; Grillo, C; Lombardi, M; Mercurio, A; Nonino, M

    2016-01-01

    We use high-precision kinematic and lensing measurements of the total mass profile of the dynamically relaxed galaxy cluster MACS J1206.2-0847 at $z=0.44$ to estimate the value of the ratio $\\eta=\\Psi/\\Phi$ between the two scalar potentials in the linear perturbed Friedmann-Lemaitre-Robertson-Walker metric.[...] Complementary kinematic and lensing mass profiles were derived from exhaustive analyses using the data from the Cluster Lensing And Supernova survey with Hubble (CLASH) and the spectroscopic follow-up with the Very Large Telescope (CLASH-VLT). Whereas the kinematic mass profile tracks only the time-time part of the perturbed metric (i.e. only $\\Phi$), the lensing mass profile reflects the contribution of both time-time and space-space components (i.e. the sum $\\Phi+\\Psi$). We thus express $\\eta$ as a function of the mass profiles and perform our analysis over the radial range $0.5\\,Mpc\\le r\\le r_{200}=1.96\\,Mpc$. Using a spherical Navarro-Frenk-White mass profile, which well fits the data, we obtain $...

  10. Deep Impact High Resolution Optical Spectroscopy with the ESO VLT and the Keck 1 telescope

    CERN Document Server

    Jehin, E; Cochran, A L; Hutsemékers, D; Jackson, W M; Manfroid, J; Rauer, H; Schulz, R; Zucconi, J M

    2006-01-01

    We report on observations of comet 9P/Tempel 1 carried out before, during, and after the NASA DEEP IMPACT event (UT July 4), with the optical spectrometers UVES and HIRES mounted on the telescopes Kueyen of the ESO VLT (Chile) and Keck 1 on Mauna Kea (Hawaii), respectively. A total observing time of about 60 hours, distributed over 15 nights around the impact date, allowed us (i) to find a periodic variation of 1.709 +/- 0.009 day in the CN and NH flux, explained by the presence of two major active regions; (ii) to derive a lifetime > ~ 5 x 10^4 s for the parent of the CN radical from a simple modeling of the CN light curve after the impact; (iii) to follow the gas and dust spatial profiles evolution during the 4 hours following the impact and derive the projected velocities (400 m/s and 150 m/s respectively); (iv) to show that the material released by the impact has the same carbon and nitrogen isotopic composition as the surface material (12C/13C = 95 +/- 15 and 14N/15N = 145 +/- 20).

  11. A Deep Optical Luminosity Function of NGC 6712 with the VLT Evidence for Severe Tidal Disruption

    CERN Document Server

    De Marchi, G; Paresce, F; Pulonen, L E; Marchi, Guido De; Leibundgut, Bruno; Paresce, Francesco; Pulone, Luigi

    1999-01-01

    The VLT on Cerro Paranal was used to observe four fields located at 2.3' from the center of the Galactic globular cluster NGC 6712 in the V and R bands. The resulting color-magnitude diagram shows a well defined main sequence reaching down to the 5 sigma detection limit at V~25, R~23.5 or approximately 4 mag below the main sequence turn-off, the deepest obtained so far on this cluster. This yields a main sequence luminosity function that peaks at M_R~4.5 and drops down to the 50% completeness limit at M_R~8.5. Transformation to a mass function via the latest mass-luminosity relation appropriate to this object indicates that the peak of the luminosity function corresponds to ~0.75 Msolar, a value significantly higher than the ~0.25 Msolar measured for most other clusters observed so far. Since this object, in its Galactic orbit, penetrates very deeply into the Galactic bulge with perigalactic distance of ~0.3 kpc, this result is the first strong evidence that tidal forces have stripped this cluster of a substa...

  12. VLT/X-shooter survey of near-infrared diffuse interstellar bands

    CERN Document Server

    Cox, N L J; Kaper, L; Ehrenfreund, P; Foing, B H; Ochsendorf, B B; van Hooff, S H M; Salama, F

    2014-01-01

    This paper presents a spectral survey of diffuse interstellar bands (DIBs) in the NIR range, from 0.9 to 2.5 micron. The observations were designed to detect new DIBs, confirm previously proposed NIR DIBs, and characterise their behaviour with respect to known line-of-sight properties (including the optical DIBs present in our spectra). X-shooter at the VLT was used to obtained medium-resolution spectra of eight known DIB targets and one telluric reference star. In addition to the known 9577, 9632, 11797, and 13175 Angstroms NIR DIBs, we confirm 9 out of the 13 NIR DIBs that were presented by Geballe and co-workers in 2011. Furthermore, we report 12 new NIR DIB candidates. The strengths of the strongest NIR DIBs show a general correlation with reddening, E(B-V), but with a large scatter. Several NIR DIBs are more strongly correlated with the 5780 Angstroms DIB strength than with E(B-V); this is especially the case for the 15268 Angstroms DIB. The NIR DIBs are strong: the summed equivalent widths of the five s...

  13. VLT/ISAAC H-band spectroscopy of embedded massive YSOs

    CERN Document Server

    Kendall, T R; Yun, J L

    2003-01-01

    We have performed intermediate resolution (R = 5000), high signal-to-noise H-band spectroscopy of a small, initial sample of three massive embedded young stellar objects (YSOs), using VLT/ISAAC. The sample has been selected from sources characterised in previous literature as being likely of OB spectral type, to be unambiguously associated with bright (H < 14) single point sources in the 2MASS database, and to have no optical counterparts. Of the targets observed, one object shows a ~B3 spectrum, similar to a main sequence object of the same spectral type. A second object exhibits weak HeI and H emission, indicating an early-type source: we detect HeII absorption, which supports a previous indirect derivation of the spectral type as mid-O. The third object does not show absorption lines, so no spectral type can de derived. It does, however, exhibit a rich spectrum of strong, broad emission lines and is likely to be surrounded by dense circumstellar material and at a very early evolutionary stage. Our resul...

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

    CERN Document Server

    Battaglia, G; Rejkuba, M

    2016-01-01

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

  15. Design, fabrication, integration and commissioning of an upgraded guiding probe for the VLT unit telescope 4

    Science.gov (United States)

    Frank, Christoph; Hammersley, Peter; Buzzoni, Bernard; Manescau, Antonio; Arsenault, Robin; Madec, Pierre-Yves; Birkmann, Martin; Mueller, Michael; Salgado, Fernando; Guisard, Stephane; Kroedel, Matthias

    2014-07-01

    As part of the preparation for the arrival of the MUSE instrument to the VLT, it was required to adapt the hosting telescope (UT4) guide probe, to increase its back focal length. This is to allow enough space for the later deployment of the MUSE Adaptive Optics module GALACSI, in-between the telescope adapter rotator and the instrument itself. The UT guide probe is a critical component for the successful operation of the telescope, so its modification to increase the telescope's back focal length, while maintaining full compatibility with the existing operation model and other hardware, was rather demanding. The design, manufacture, assembly and test for the new supporting arm in the UT guiding probe is presented. It mixes the use of novel materials (HB-CESIC® for the mirrors substrates) and state of the art manufacturing techniques (3D printing mould production and rapid casting for the support structure), which allow producing easily a high performance subsystem. Characterization of the system prior delivery to the telescope, its integration in the UT and results after commissioning is presented. Its successful implementation has validated new manufacturing techniques that may prove very useful for future instruments development.

  16. An extensive VLT/X-shooter library of photospheric templates of pre-main sequence stars

    Science.gov (United States)

    Manara, C. F.; Frasca, A.; Alcalá, J. M.; Natta, A.; Stelzer, B.; Testi, L.

    2017-09-01

    Context. Studies of the formation and evolution of young stars and their disks rely on knowledge of the stellar parameters of the young stars. The derivation of these parameters is commonly based on comparison with photospheric template spectra. Furthermore, chromospheric emission in young active stars impacts the measurement of mass accretion rates, a key quantity for studying disk evolution. Aims: Here we derive stellar properties of low-mass (M⋆≲ 2 M⊙) pre-main sequence stars without disks, which represent ideal photospheric templates for studies of young stars. We also use these spectra to constrain the impact of chromospheric emission on the measurements of mass accretion rates. The spectra are reduced, flux-calibrated, and corrected for telluric absorption, and are made available to the community. Methods: We derive the spectral type for our targets by analyzing the photospheric molecular features present in their VLT/X-shooter spectra by means of spectral indices and comparison of the relative strength of photospheric absorption features. We also measure effective temperature, gravity, projected rotational velocity, and radial velocity from our spectra by fitting them with synthetic spectra with the ROTFIT tool. The targets have negligible extinction (AVhttp://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/605/A86

  17. VLT\\/UVES Abundances in Four Nearby Dwarf Spheroidal Galaxies II. Implications for Understanding Galaxy Evolution

    CERN Document Server

    Tolstoy, E; Shetrone, M; Primas, F; Hill, V; Szeifert, A K T; Tolstoy, Eline

    2003-01-01

    We have used UVES on VLT-UT2 to take spectra of 15 individual red giant stars in the centers of four nearby dwarf spheroidal galaxies: Sculptor, Fornax, Carina and Leo I. We measure the abundance variations of numerous elements in these low mass stars with a range of ages (1-15Gyr old). This means that we can effectively measure the chemical evolution of these galaxies WITH TIME. Our results show a significant spread in metallicity with age, but an overall trend consistent with what might be expected from a closed (or perhaps leaky) box chemical evolution scenario over the last 10-15Gyr. We notice that each of these galaxies show broadly similar abundance patterns for all elements measured. This suggests a fairly uniform progression of chemical evolution with time, despite quite a large range of star formation histories. It seems likely that these galaxies had similar initial conditions, and evolve in a similar manner with star formation occurring at a uniformly low rate, even if at different times. With our ...

  18. A VLT/NACO Study of Star Formation in the Massive Embedded Cluster RCW 38

    CERN Document Server

    DeRose, K L; Gutermuth, R A; Wolk, S J; Megeath, S T; Alves, J; Nürnberger, D

    2009-01-01

    We present adaptive optics (AO) near-infrared (JHKs) observations of the deeply embedded massive cluster RCW 38 using NACO on the VLT. Narrowband AO observations centered at wavelengths of 1.28, 2.12, and 2.17 micron were also obtained. The area covered by these observations is about 0.5 pc square, centered on the O star RCW 38 IRS2. We use the JHKs colors to identify young stars with infrared excess. Through a detailed comparison to a nearby control field, we find that most of the 337 stars detected in all three infrared bands are cluster members (~317), with essentially no contamination due to background or foreground sources. Five sources have colors suggestive of deeply embedded protostars, while 53 sources are detected at Ks only; their spatial distribution with respect to the extinction suggests they are highly reddened cluster members. Detectable Ks-band excess is found toward 29 +/- 3 % of the stars. For comparison to a similar area of Orion observed in the near-infrared, mass and extinction cuts are ...

  19. VLT/UVES Observations of Interstellar Molecules and Diffuse Bands in the Magellanic Clouds

    CERN Document Server

    Welty, D E; Gredel, R; Lambert, D L; Thorburn, J A

    2006-01-01

    We discuss the abundances of interstellar CH, CH+, and CN in the Magellanic Clouds (MC), derived from spectra of 7 SMC and 13 LMC stars obtained (mostly) with the VLT/UVES. CH and/or CH+ are detected toward 3 SMC and 9 LMC stars; CN is detected toward 2 stars. In the MC, the CH/H2 ratio is comparable to that found for diffuse Galactic molecular clouds in some sight lines, but is lower by factors up to 10-15 in others. The abundance of CH in the MC thus appears to depend on local physical conditions -- and not just on metallicity. The observed relationships between the column density of CH and those of CN, CH+, Na I, and K I in the MC are generally consistent with the trends observed in our Galaxy. Using existing data for the rotational populations of H2, we estimate temperatures, radiation field strengths, and local hydrogen densities for the diffuse molecular gas. Densities estimated from N(CH), assuming that CH is produced via steady-state gas-phase reactions, are considerably higher; much better agreement ...

  20. VLT Observations Confirm that the Universe Was Hotter in the Past

    Science.gov (United States)

    2000-12-01

    UVES Measures the Cosmic Temperature 12 Billion Years Ago Summary A fundamental prediction of the Big Bang theory has finally been verified . For the first time, an actual measurement has been made of the temperature of the cosmic microwave background radiation, at a time when the Universe was only about 2.5 billion years old . This fundamental and very difficult observation was achieved by a team of astronomers from India, France and ESO [1]. They obtained a detailed spectrum of a quasar in the distant Universe, using the UV-Visual Echelle Spectrograph (UVES) instrument at the ESO 8.2-m VLT KUEYEN telescope at the Paranal Observatory. If the Universe was indeed formed in a Big Bang, as most astrophysicists believe, the glow of this primeval fireball should have been warmer in the past. This is exactly what is found by the new measurements. The analysis of the VLT spectrum of the distant quasar not only gives the definitive proof of the presence of the relict radiation in the early Universe, it also shows that it was indeed significantly warmer than it is today, as predicted by the theory. PR Photo 35/00 : VLT spectrum of the distant quasar PKS 1232+0815 , displaying lines of carbon atoms from an intervening cloud in which the cosmic temperature was measured. The Cosmic Microwave Background Radiation (CMBR) One of the fundamental predictions of the Hot Big Bang theory for the creation of the Universe is the existence of the Cosmic Microwave Background Radiation (CMBR) . This relict radiation of the primeval fireball was discovered in 1964 by means of radio observations by American physicists Arno A. Penzias and Robert W. Wilson , who were rewarded with the Nobel Prize in 1978. Precision measurements by the COBE satellite later showed that this ancient radiation fills the Universe, with a present-day temperature of slightly less than 3 degrees above the absolute zero (2.7 K [Kelvin], or -270.4 °C). This radiation comes from all directions and is extremely uniform

  1. Effects of side walls on facade flame entrainment and flame height from opening in compartment fires

    Directory of Open Access Journals (Sweden)

    Hu L.H.

    2013-11-01

    Full Text Available This paper presents an investigation of the side wall effects on facade flames ejected from the opening (such as a window of an under-ventilated room fire. Experiments are carried out in a reduced-scale experimental setup, consisting of a cubic fire compartment having an opening with a vertical facade wall and two side walls normal to the façade wall. By changing the distance of the two side walls, the facade flame heights for different opening conditions (width, height are recorded by a CCD camera. It is found that as the distance of the two side walls decreases the behavior the flame height can be distinguished into two regimes characterized by the dimensionless excess heat release rate, $skew5dot{Q}_{ex}^{ast}$ See Formula in PDF , outside the opening: (a for the “wall fire” (skew5dot{Q}_{ex}^{ast }$See Formula in PDF ≤ 1.3 , the flame height is shown to change little with decrease of side wall distance as the dominant entrainment is from the front direction (normal to the facade wall independent of the side wall distances; (b for the “axis-symmetrical fire” (\\skew5dot{Q}_{ex}^{ast}$ > 1.3, the flame height increases significantly with a decrease in side wall distance as both the entrainment from the two side directions (parallel to the facade wall and that from the front direction (normal to the facade wall together apply. A global physically based non-dimensional factor K is then brought forward based on the side wall constraint effect on the facade flame entrainment to characterize the side wall effect on the flame height, by accounting for the dimensionless excess heat release rate, the characteristic length scales of the opening as well as the side wall separation distance. The experimental data for different opening dimensions and side wall distances collapse by using this global non-dimensional factor.

  2. Hubble Tarantula Treasury Project. III. Photometric Catalog and Resulting Constraints on the Progression of Star Formation in the 30 Doradus Region

    CERN Document Server

    Sabbi, E; Anderson, J; Cignoni, M; van der Marel, R P; Zaritsky, D; de Marchi, G; Panagia, N; Gouliermis, D A; Grebel, E K; Gallager, J S; Smith, L J; Sana, H; Aloisi, A; Tosi, M; Evans, C J; Arab, H; Boyer, M; de Mink, S E; Gordon, K; Koekemoer, A M; Larsen, S S; Ryon, J E; Zeidler, P

    2015-01-01

    We present and describe the astro-photometric catalog of more than 800,000 sources found in the Hubble Tarantula Treasury Project (HTTP). HTTP is a Hubble Space Telescope (HST) Treasury program designed to image the entire 30 Doradus region down to the sub-solar (~0.5 solar masses) mass regime using the Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS). We observed 30 Doradus in the near ultraviolet (F275W, F336W), optical (F555W, F658N, F775W), and near infrared (F110W, F160W) wavelengths. The stellar photometry was measured using point-spread function (PSF) fitting across all the bands simultaneously. The relative astrometric accuracy of the catalog is 0.4 mas. The astro-photometric catalog, results from artificial star experiments and the mosaics for all the filters are available for download. Color-magnitude diagrams are presented showing the spatial distributions and ages of stars within 30 Dor as well as in the surrounding fields. HTTP provides the first rich and statistically signifi...

  3. Structural and Functional Diversity of Peptide Toxins from Tarantula Haplopelma hainanum (Ornithoctonus hainana) Venom Revealed by Transcriptomic, Peptidomic, and Patch Clamp Approaches.

    Science.gov (United States)

    Zhang, Yi-Ya; Huang, Yong; He, Quan-Ze; Luo, Ji; Zhu, Li; Lu, Shan-Shan; Liu, Jin-Yan; Huang, Peng-Fei; Zeng, Xiong-Zhi; Liang, Song-Ping

    2015-05-29

    Spider venom is a complex mixture of bioactive peptides to subdue their prey. Early estimates suggested that over 400 venom peptides are produced per species. In order to investigate the mechanisms responsible for this impressive diversity, transcriptomics based on second generation high throughput sequencing was combined with peptidomic assays to characterize the venom of the tarantula Haplopelma hainanum. The genes expressed in the venom glands were identified, and the bioactivity of their protein products was analyzed using the patch clamp technique. A total of 1,136 potential toxin precursors were identified that clustered into 90 toxin groups, of which 72 were novel. The toxin peptides clustered into 20 cysteine scaffolds that included between 4 and 12 cysteines, and 14 of these groups were newly identified in this spider. Highly abundant toxin peptide transcripts were present and resulted from hypermutation and/or fragment insertion/deletion. In combination with variable post-translational modifications, this genetic variability explained how a limited set of genes can generate hundreds of toxin peptides in venom glands. Furthermore, the intraspecies venom variability illustrated the dynamic nature of spider venom and revealed how complex components work together to generate diverse bioactivities that facilitate adaptation to changing environments, types of prey, and milking regimes in captivity.

  4. Assessing Pediatric Nurses' Knowledge About Chemical Flame Retardants.

    Science.gov (United States)

    Distelhorst, Laura; Bieda, Amy; DiMarco, Marguerite; Tullai-McGuinness, Susan

    Chemical flame retardants are routinely applied to children's products and are harmful to their health. Pediatric nurses are in a key position to provide education to caregivers on methods to decrease their children's exposure to these harmful chemicals. However, a critical barrier is the absence of any program to educate nurses about chemical flame retardants. In order to overcome this barrier, we must first assess their knowledge. This article provides key highlights every pediatric nurse should know about chemical flame retardants and reports the results of a knowledge assessment study. The purpose of this study was to (1) assess pediatric nurses' knowledge of chemical flame retardants, (2) determine what topic areas of chemical flame retardants pediatric nurses lack knowledge in, and (3) determine the best method to educate nurses about chemical flame retardants. A single sample cross-sectional questionnaire design was used. A total sample of 417 advanced practice registered nurses and registered nurses completed an online survey about chemical flame retardants. Pediatric nurses' knowledge of chemical flame retardants was low (M=13.4 out of 51). Articles, webinars, and e-mails were the primary preferred methods for education on the subject identified as a result of the survey. Pediatric nurses have a large knowledge deficit related to chemical flame retardants. The data collected from this study will help structure future educational formats for pediatric nurses on chemical flame retardants to increase their knowledge. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Flame Retardation Modification of Paper-Based PVC Wallcoverings

    Directory of Open Access Journals (Sweden)

    Lin Hui

    2016-01-01

    Full Text Available The flame-retarded paper-based polyvinyl chloride (PVC wallcoverings were successfully prepared, using plant fiber paper as base material and adding inorganic flame retardants and flame-retarded plasticizer as additives. Flame retardancy, thermostability, smoke suppression and mechanical properties were tested regarding to the prepared wallcoverings. The results showed that 2ZnO·3B2O3·3.5H2O could improve flame retardancy and thermostability of paper-based PVC wallcoverings; plasticizer tricresyl phosphate increased flame retardancy of the prepared materials auxiliarily. Also, flame-retarded paper-based PVC wallcoverings with higher flame retardancy, smoke suppression and mechanical property was prepared using plant fiber paper with fix quantity of 90 g/m3 as base material, using 2ZnO·3B2O3·3.5H2O as inorganic flame retardant, and using tricresyl phosphate as plasticizer. For the flame-retarded paper-based PVC wallcoverings in this study, the limit oxygen index (LOI reaches 32.3, maximal smoke density is 16.91 %, and the horizontal and longitudinal wet tensile strength reaches 1.38 kN·m−1 and 1.51 kN·m−1 respectively. Meanwhile, its flame retardancy meets the requirements about flame retardancy for material Class B1 listed in Chinese National Standards GB 8624-2012, Classification for burning behavior of building materials and products. This research creates an effective path to prepare paper-based PVC wallcoverings with high flame retardancy.

  6. Early structure of LPG partially premixed conically stabilized flames

    KAUST Repository

    Elbaz, Ayman M.

    2013-01-01

    This paper presents experimental investigation of LPG partially premixed turbulent flames stabilized within a conical nozzle burner under constant degree of partial premixing. The stability limits and mean flame structure are presented based on the mean gas temperature and the concentration of CO, O 2, NO, and HC at the flame early region of reaction. The investigation covered the influence of the nozzle cone angle, the jet exit velocity and the jet equivalence ratio. The stability results show that the flames with cone are more stable than those without cone. For conical stabilized flames, the stability results exhibit three different sensitivity regions between the jet velocity and equivalence ratio. The inflame measurements prove that the flame stability could be attributed to the triple flame structure at the flame leading edge. The data show that the triple flame structure is influenced by cone angle, the jet velocity and the equivalence ratio. The flame is believed to be controlled by the recirculation flow inside the cone. Increasing the cone angle induced higher air entrainment to the reaction zone as depicted by a higher O 2 concentration within the flame leading edge. Increasing the jet velocity to a certain limit enhances the intensity of combustion at the flame leading edge, while excessive increase in jet velocity reduces this intensity. At a fixed jet velocity the higher the equivalence ratio, the higher the amount of fuel diffused and engulfed to the reaction zone, the more delay of the combustion completion and the higher the emission concentrations of the flame. © 2012 Elsevier Inc.

  7. Flame spread over inclined electrical wires with AC electric fields

    KAUST Repository

    Lim, Seung J.

    2017-07-21

    Flame spread over polyethylene-insulated electrical wires was studied experimentally with applied alternating current (AC) by varying the inclination angle (θ), applied voltage (VAC), and frequency (fAC). For the baseline case with no electric field applied, the flame spread rate and the flame width of downwardly spreading flames (DSFs) decreased from the horizontal case for −20° ≤ θ < 0° and maintained near constant values for −90° ≤ θ < −20°, while the flame spread rate increased appreciably as the inclination angle of upwardly spreading flames (USFs) increased. When an AC electric field was applied, the behavior of flame spread rate in DSFs (USFs) could be classified into two (three) sub-regimes characterized by various functional dependences on VAC, fAC, and θ. In nearly all cases of DSFs, a globular molten polyethylene formed ahead of the spreading flame edge, occasionally dripping onto the ground. In these cases, an effective flame spread rate was defined to represent the burning rate by measuring the mass loss due to dripping. This effective spread rate was independent of AC frequency, while it decreased linearly with voltage and was independent of the inclination angle. In DSFs, when excessively high voltage and frequency were applied, the dripping led to flame extinction during propagation and the extinction frequency correlated well with applied voltage. In USFs, when high voltage and frequency were applied, multiple globular molten PEs formed at several locations, leading to ejections of multiple small flame segments from the main flame, thereby reducing the flame spread rate, which could be attributed to the electrospray phenomenon.

  8. Numerical study of laminar nonpremixed methane flames in coflow jets: Autoignited lifted flames with tribrachial edges and MILD combustion at elevated temperatures

    KAUST Repository

    M. Al-Noman, Saeed

    2016-07-07

    Autoignition characteristics of laminar nonpremixed methane jet flames in high-temperature coflow air are studied numerically. Several flame configurations are investigated by varying the initial temperature and fuel mole fraction. At a relatively low initial temperature, a non-autoignited nozzle-attached flame is simulated at relatively low jet velocity. When the initial temperature is higher than that required for autoignition, two regimes are investigated: an autoignited lifted flame with tribrachial edge structure and an autoignited lifted flame with Mild combustion. The autoignited lifted flame with tribrachial edge exhibited three branches: lean and rich premixed flame wings and a trailing diffusion flame. Characteristics of kinetic structure for autoignited lifted flames are discussed based on the kinetic structures of homogeneous autoignition and flame propagation of stoichiometric mixture. Results showed that a transition from autoignition to flame propagation modes occurs for reasonably stoichiometric mixtures. The autoignited lifted flame with Mild combustion occurs when methane fuel is highly diluted with nitrogen. The kinetic structure analysis shows that the characteristics of Mild combustion can be treated as an autoignited lean premixed lifted flame. Transition behavior from Mild combustion to nozzle-attached flame was investigated by increasing the fuel mole fraction. As the maximum flame temperature increases with decreasing liftoff height, the kinetic structure showed a transition behavior from autoignition to flame propagation of a lean premixed flame. © 2016 The Combustion Institute

  9. Influence of Pilot Flame Parameters on the Stability of Turbulent Jet Flames

    KAUST Repository

    Guiberti, Thibault F.

    2016-11-08

    This paper presents a comprehensive study of the effects of pilot parameters on flame stability in a turbulent jet flame. The Sydney inhomogeneous piloted burner is employed as the experimental platform with two main fuels, namely, compressed natural gas and liquefied petroleum gas. Various concentrations of five gases are used in the pilot stream, hydrogen, acetylene, oxygen, nitrogen, and argon, to enable a sufficient range in exploring the following parameters: pilot heat release, temperature, burnt gas velocity, equivalence ratio, and H/C ratio. The experimental results are mainly presented in the form of blow-off limits and supported by simple calculations, which simulate various conditions of the pilot–mixture interface. It is found that increasing the pilot adiabatic flame temperature benefits the flame stability and has an even greater influence than the heat release, which is also known to enhance the blow-off limits. Conversely, increasing the pilot burnt gas velocity reduces the blow-off velocity, except for the limiting case when the jet is fully non-premixed. The H/C ratio has negligible effects, while resorting to lean pilots significantly increases the stability of globally rich partially premixed and premixed jets. Such findings are consistent with trends obtained from laminar flame calculations for rich fuel/air mixtures issuing against hot combustion products to simulate the pilot stream.

  10. CoFlame: A refined and validated numerical algorithm for modeling sooting laminar coflow diffusion flames

    Science.gov (United States)

    Eaves, Nick A.; Zhang, Qingan; Liu, Fengshan; Guo, Hongsheng; Dworkin, Seth B.; Thomson, Murray J.

    2016-10-01

    Mitigation of soot emissions from combustion devices is a global concern. For example, recent EURO 6 regulations for vehicles have placed stringent limits on soot emissions. In order to allow design engineers to achieve the goal of reduced soot emissions, they must have the tools to so. Due to the complex nature of soot formation, which includes growth and oxidation, detailed numerical models are required to gain fundamental insights into the mechanisms of soot formation. A detailed description of the CoFlame FORTRAN code which models sooting laminar coflow diffusion flames is given. The code solves axial and radial velocity, temperature, species conservation, and soot aggregate and primary particle number density equations. The sectional particle dynamics model includes nucleation, PAH condensation and HACA surface growth, surface oxidation, coagulation, fragmentation, particle diffusion, and thermophoresis. The code utilizes a distributed memory parallelization scheme with strip-domain decomposition. The public release of the CoFlame code, which has been refined in terms of coding structure, to the research community accompanies this paper. CoFlame is validated against experimental data for reattachment length in an axi-symmetric pipe with a sudden expansion, and ethylene-air and methane-air diffusion flames for multiple soot morphological parameters and gas-phase species. Finally, the parallel performance and computational costs of the code is investigated.

  11. Flame Retardant Polyamide Fibres: The Challenge of Minimising Flame Retardant Additive Contents with Added Nanoclays

    Directory of Open Access Journals (Sweden)

    Richard Horrocks

    2016-08-01

    Full Text Available This work shows that halogen-free, flame retarded polyamide 6 (PA6, fabrics may be produced in which component fibres still have acceptable tensile properties and low levels (preferably ≤10 wt % of additives by incorporating a nanoclay along with two types of flame retardant formulations. The latter include (i aluminium diethyl phosphinate (AlPi at 10 wt %, known to work principally in the vapour phase and (ii ammonium sulphamate (AS/dipentaerythritol (DP system present at 2.5 and 1 wt % respectively, believed to be condense phase active. The nanoclay chosen is an organically modified montmorillonite clay, Cloisite 25A. The effect of each additive system is analysed in terms of its ability to maximise both filament tensile properties relative to 100% PA6 and flame retardant behaviour of knitted fabrics in a vertical orientation. None of the AlPi-containing formulations achieved self-extinguishability, although the presence of nanoclay promoted lower burning and melt dripping rates. The AS/DP-containing formulations with total flame retardant levels of 5.5 wt % or less showed far superior properties and with nanoclay, showed fabric extinction times ≤ 39 s and reduced melt dripping. The tensile and flammability results, supported by thermogravimetric analysis, have been interpreted in terms of the mechanism of action of each flame retardant/nanoclay type.

  12. Flame-in-gas-shield and miniature diffusion flame hydride atomizers for atomic fluorescence spectrometry: optimization and comparison

    Energy Technology Data Exchange (ETDEWEB)

    Marschner, Karel, E-mail: karel.marschner@biomed.cas.cz [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic); Charles University in Prague, Faculty of Science, Department of Analytical Chemistry, Albertov 8, 128 43 Prague (Czech Republic); Musil, Stanislav; Dědina, Jiří [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic)

    2015-07-01

    A detailed optimization of relevant experimental parameters of two hydride atomizers for atomic fluorescence spectrometry: flame-in-gas-shield atomizer with a two-channel shielding unit and a standard atomizer for atomic fluorescence spectrometry, miniature diffusion flame, was performed. Arsine, generated by the reaction with NaBH{sub 4} in a flow injection arrangement, was chosen as the model hydride. Analytical characteristics of both the atomizers (sensitivity, noise, limits of detection) were compared. Under optimum conditions sensitivity obtained with flame-in-gas-shield atomizer was approximately twice higher than with miniature diffusion flame. The additional advantage of flame-in-gas-shield atomizer is significantly lower flame emission resulting in a better signal to noise ratio. The resulting arsenic limits of detection for miniature diffusion flame and flame-in-gas-shield atomizer were 3.8 ng l{sup −1} and 1.0 ng l{sup −1}, respectively. - Highlights: • We optimized and compared two hydride atomizers for atomic fluorescence spectrometry. • Miniature diffusion flame and flame-in-gas-shield atomizer were optimized. • The limit of detection for arsenic was 1.0 ng l{sup −1}.

  13. Analytical study in the mechanism of flame movement in horizontal tubes. II. Flame acceleration in smooth open tubes

    CERN Document Server

    Kazakov, Kirill A

    2013-01-01

    The problem of spontaneous acceleration of premixed flames propagating in open horizontal tubes with smooth walls is revisited. It is proved that in long tubes, this process can be considered quasi-steady, and an equation for the flame front position is derived using the on-shell description. Numerical solutions of this equation are found which show that as in the case of uniform flame movement, there are two essentially different regimes of flame propagation. In the type I regime, the flame speed and its acceleration are comparatively low, whereas the type II regime is characterized by significant flame acceleration that rapidly increases as the flame travels along the tube. A detailed comparison of the obtained results with the experimental data on flame acceleration in methane-air mixtures is given. In particular, it is confirmed that flames propagating in near-stoichiometric mixtures and mixtures near the limits of inflammability belong to the types II and I, respectively, whereas flames in transient mixt...

  14. Flame Imaging of Gas-Turbine Relight

    DEFF Research Database (Denmark)

    Read, Robert; Rogerson, J.W.; Hochgreb, S.

    2010-01-01

    High-altitude relight inside a lean-direct-injection gas-turbine combustor is investigated experimentally by highspeed imaging. Realistic operating conditions are simulated in a ground-based test facility, with two conditions being studied: one inside and one outside the combustor ignition loop....... The motion of hot gases during the early stages of relight is recorded using a high-speed camera. An algorithm is developed to track the flame movement and breakup, revealing important characteristics of the flame development process, including stabilization timescales, spatial trajectories, and typical...... velocities of hot gas motion. Although the observed patterns of ignition failure are in broad agreement with results from laboratory-scale studies, other aspects of relight behavior are not reproduced in laboratory experiments employing simplified flow geometries and operating conditions. For example, when...

  15. Parametric Erosion Investigation: Propellant Adiabatic Flame Temperature

    Directory of Open Access Journals (Sweden)

    P. J. Conroy

    2002-01-01

    Full Text Available The influence of quasi-independent parameters and their potential influence on erosion in guns have been investigated. Specifically, the effects of flame temperature and the effect of assuming that the Lewis number (ratio of mass-to-heat transport to the surface, Le = 1, has been examined. The adiabatic flame temperature for a propellant was reduced by the addition of a diluent from a high temperature of 3843 K (similar to that of M9 down to 3004 K, which is near the value for M30A1 propellant. Mass fractions of critical species at the surface with and without the assumption of Le = 1 are presented, demonstrating that certain species preferentially reach the surface providing varied conditions for the surface reactions. The results for gun tube bore surface regression qualitatively agree with previous studies and with current experimental data.

  16. The advanced flame quality indicator system

    Energy Technology Data Exchange (ETDEWEB)

    Oman, R.; Rossi, M.J.; Calia, V.S.; Davis, F.L.; Rudin, A. [Insight Technologies, Inc., Bohemia, NY (United States)

    1997-09-01

    By combining oil tank monitoring, systems diagnostics and flame quality monitoring in an affordable system that communicates directly with dealers by telephone modem, Insight Technologies offers new revenue opportunities and the capability for a new order of customer relations to oil dealers. With co-sponsorship from New York State Energy Research and Development Authority, we have incorporated several valuable functions to a new product based on the original Flame Quality Indicator concept licensed from the US DOE`s Brookhaven National Laboratory. The new system is the Advanced Flame Quality Indicator, or AFQI. As before, the AFQI monitors and reports the intensity of the burner flame relative to a calibration established when the burner is set up at AFQI installation. Repairs or adjustments are summoned by late-night outgoing telephone calls when limits are exceeded in either direction, indicating an impending contamination or other malfunction. A independently, a pressure transducer for monitoring oil tank level and filter condition, safety lockout alarms and a temperature monitor; all reporting automatically at instructed intervals via an on-board modem to a central station PC computer (CSC). Firmware on each AFQI unit and Insight-supplied software on the CSC automatically interact to maintain a customer database for an oil dealer, an OEM, or a regional service contractor. In addition to ensuring continuously clean and efficient operation, the AFQI offers the oil industry a new set of immediate payoffs, among which are reduced outages and emergency service calls, shorter service calls from cleaner operation, larger oil delivery drops, the opportunity to stretch service intervals to as along as three years in some cases, new selling features to keep and attract customers, and greatly enhanced customer contact, quality and reliability.

  17. Soot Deposit Properties in Practical Flames

    Energy Technology Data Exchange (ETDEWEB)

    Preciado, Ignacio [University of Utah; Eddings, Eric G. [University of Utah; Sarofim, Adel F. [University of Utah; Dinwiddie, Ralph Barton [ORNL; Porter, Wallace D [ORNL; Lance, Michael J [ORNL

    2009-01-01

    Soot deposition from hydrocarbon flames was investigated in order to evaluate the evolution of the deposits during the transient process of heating an object that starts with a cold metal surface that is exposed to a flame. The study focused on the fire/metal surface interface and the critical issues associated with the specification of the thermal boundaries at this interface, which include the deposition of soot on the metal surface, the chemical and physical properties of the soot deposits and their subsequent effect on heat transfer to the metal surface. A laboratory-scale device (metallic plates attached to a water-cooled sampling probe) was designed for studying soot deposition in a laminar ethylene-air premixed flame. The metallic plates facilitate the evaluation of the deposition rates and deposit characteristics such as deposit thickness, bulk density, PAH content, deposit morphology, and thermal properties, under both water-cooled and uncooled conditions. Additionally, a non-intrusive Laser Flash Technique (in which the morphology of the deposit is not modified) was used to estimate experimental thermal conductivity values for soot deposits as a function of deposition temperature (water-cooled and uncooled experiments), location within the flame and chemical characteristics of the deposits. Important differences between water-cooled and uncooled surfaces were observed. Thermophoresis dominated the soot deposition process and enhanced higher deposition rates for the water-cooled experiments. Cooler surface temperatures resulted in the inclusion of increased amounts of condensable hydrocarbons in the soot deposit. The greater presence of condensable material promoted decreased deposit thicknesses, larger deposit densities, different deposit morphologies, and higher thermal conductivities.

  18. Computational and experimental study of laminar flames

    Energy Technology Data Exchange (ETDEWEB)

    Smooke, Mitchell [Yale Univ., New Haven, CT (United States)

    2015-05-29

    During the past three years, our research has centered on an investigation of the effects of complex chemistry and detailed transport on the structure and extinction of hydrocarbon flames in coflowing axisymmetric configurations. We have pursued both computational and experimental aspects of the research in parallel on both steady-state and time-dependent systems. The computational work has focused on the application of accurate and efficient numerical methods for the solution of the steady-state and time-dependent boundary value problems describing the various reacting systems. Detailed experimental measurements were performed on axisymmetric coflow flames using two-dimensional imaging techniques. Previously, spontaneous Raman scattering, chemiluminescence, and laser-induced fluorescence were used to measure the temperature, major and minor species profiles. Particle image velocimetry (PIV) has been used to investigate velocity distributions and for calibration of time-varying flames. Laser-induced incandescence (LII) with an extinction calibration was used to determine soot volume fractions, while soot surface temperatures were measured with three-color optical pyrometry using a color digital camera. A blackbody calibration of the camera allows for determination of soot volume fraction as well, which can be compared with the LII measurements. More recently, we have concentrated on a detailed characterization of soot using a variety of techniques including time-resolved LII (TiRe-LII) for soot primary particles sizes, multi-angle light scattering (MALS) for soot radius of gyration, and spectrally-resolved line of sight attenuation (spec-LOSA). Combining the information from all of these soot measurements can be used to determine the soot optical properties, which are observed to vary significantly depending on spatial location and fuel dilution. Our goal has been to obtain a more fundamental understanding of the important fluid dynamic and chemical interactions in

  19. Flexible PVC flame retarded with expandable graphite

    CSIR Research Space (South Africa)

    Focke, WW

    2014-02-01

    Full Text Available by the polymer matrix and the exfoliating graphite prevents the formation of a flammable air fuel mixture. Keywords: Expandable graphite; graphite oxide; graphite intercalation compound; exfoliation; thermal analysis ________________ *Corresponding author: Tel... char residue [6] and this contributes to the mechanisms of flame retardant action [5]. Expandable graphite (EG) is a partially oxidized form of graphite containing intercalated guest species (e.g., sulfuric acid anions) in-between the stacked...

  20. Thermal Insulation System for Large Flame Buckets

    Science.gov (United States)

    Callens, E. Eugene, Jr.; Gamblin, Tonya Pleshette

    1996-01-01

    The objective of this study is to investigate the use of thermal protection coatings, single tiles, and layered insulation systems to protect the walls of the flame buckets used in the testing of the Space Shuttle Main Engine, while reducing the cost and maintenance of the system. The physical behavior is modeled by a plane wall boundary value problem with a convective frontface condition and a backface condition designed to provide higher heat rates through the material.

  1. Physical and Chemical Processes in Flames

    Science.gov (United States)

    2007-09-01

    reaction rate constants was developed to model these measured laminar flame speeds as well as a wide spectrum of other experimental data. The kinetic ...temperatures of dimethyl ether ( DME ) and 1,3-butadiene, allowing developments of detailed and reduced reaction mechanisms. A mathematical theory and...and improvement of the existing reaction mechanisms. Furthermore, the ignition temperatures of counterflowing dimethyl ether ( DME ) and 1,3-butadiene

  2. The research of far infrared flame retardant polyester staple fiber

    Science.gov (United States)

    Li, Qingshan; Zhang, Kaijun; Luo, Jinqong; Li, Ji’an; Jiang, Jian; Liang, Qianqian; Jin, Yongxia; Liu, Bing

    2017-01-01

    Far infrared flame retardant slices was prepared, fiber with far infrared flame retardant composite function was also prepared by the method of melt spinning. Scanning electron microscopy (SEM) was used to observe the fibrous microscopic structure. In the SEM images, functional ultrafine powder particle size and distribution in the fiber were visible. The results show that the functional ultrafine powder is evenly distributed on the fibrous surface, which is closely combined with fiber, and the far infrared emissivity is F, which is more than (8 to 14 microns) 0.88. Far infrared flame retardant polyester fiber has not only good flame retardant, but also environmental health effect: releasing negative ions and launch far-infrared, which shows wide application prospect. The fiber was processed into far-infrared flame retardant electric blanket, whose functional indicators and flame retardant properties are not reduced.

  3. New developments in the theory of flame propagation

    Energy Technology Data Exchange (ETDEWEB)

    Sivashinsky, G.I. [City College of the City Univ. of New York, NY (United States)

    1996-12-31

    Two topics in combustion fluid mechanics are discussed. The first is a theory of the outward propagating spherical flame in the regime of well-developed hydrodynamic instability. In a qualitative agreement with experimental observations it is shown that the flame assumes a fractal-like wrinkled structure resulting in the overall burning rate acceleration. In contrast to hydrodynamically unstable flames, the expanding flame subject exclusively to the effect of diffusive instability does not indicate any disposition toward acceleration. The second topic concerns the dynamics of diffusively unstable flames subjected to radiative heat losses. At high enough heat losses the flame breaks up into separate self-propagating cap-like flamelets while a significant portion of the fuel remains unconsumed.

  4. Real-time Flame Rendering with GPU and CUDA

    Directory of Open Access Journals (Sweden)

    Wei Wei

    2011-02-01

    Full Text Available This paper proposes a method of flame simulation based on Lagrange process and chemical composition, which was non-grid and the problems associated with there grids were overcome. The turbulence movement of flame was described by Lagrange process and chemical composition was added into flame simulation which increased the authenticity of flame. For real-time applications, this paper simplified the EMST model. GPU-based particle system combined with OpenGL VBO and PBO unique technology was used to accelerate finally, the speed of vertex and pixel data interaction between CPU and GPU increased two orders of magnitude, frame rate of rendering increased by 30%, which achieved fast dynamic flame real-time simulation. For further real-time applications, this paper presented a strategy to implement flame simulation with CUDA on GPU, which achieved a speed up to 2.5 times the previous implementation.

  5. Camera calibration for multidirectional flame chemiluminescence tomography

    Science.gov (United States)

    Wang, Jia; Zhang, Weiguang; Zhang, Yuhong; Yu, Xun

    2017-04-01

    Flame chemiluminescence tomography (FCT), which combines computerized tomography theory and multidirectional chemiluminescence emission measurements, can realize instantaneous three-dimensional (3-D) diagnostics for flames with high spatial and temporal resolutions. One critical step of FCT is to record the projections by multiple cameras from different view angles. For high accuracy reconstructions, it requires that extrinsic parameters (the positions and orientations) and intrinsic parameters (especially the image distances) of cameras be accurately calibrated first. Taking the focus effect of the camera into account, a modified camera calibration method was presented for FCT, and a 3-D calibration pattern was designed to solve the parameters. The precision of the method was evaluated by reprojections of feature points to cameras with the calibration results. The maximum root mean square error of the feature points' position is 1.42 pixels and 0.0064 mm for the image distance. An FCT system with 12 cameras was calibrated by the proposed method and the 3-D CH* intensity of a propane flame was measured. The results showed that the FCT system provides reasonable reconstruction accuracy using the camera's calibration results.

  6. Wind measurements in Saturn's atmosphere with UVES/VLT ground-based Doppler velocimetry

    Science.gov (United States)

    Machado, Pedro; Silva, Miguel; Peralta, Javier; Luz, David; Sánchez-Lavega, Agustin; Hueso, Ricardo

    2016-04-01

    We will present preliminary Doppler wind velocity results of Saturn's zonal flow at cloud level. Our aim is help to constrain the characterization of the equatorial jet at cloud level and the latitudinal variation of the zonal winds, to measure its spatial and temporal variability, to contribute to monitor the variability in order to achieve a better understanding of the dynamics of Saturn's zonal winds, whose equatorial jet has a complex vertical structure and temporal variability (Sanchez-Lavega et al., Nature, 423, 623, 3003; Garcia-Melendo et al., Geophys. Res. Lett., 37, L22204. 2010). Finally, the complementarity with Cassini, providing an independent set of observations. The UVES/VLT instrument has been used, which simultaneously achieves high spectral resolving power and high spatial resolution. The field has been derotated in order to have the aperture aligned perpendicularly to Saturn's rotation axis. In this configuration, spatial information in the East-West direction is preserved in a set of spectra in the direction perpendicular to dispersion. The technique of absolute accelerometry (AA, Connes, 1985, ApSS 110, 211) has been applied to the backscattered solar spectrum in order to determine the Doppler shift associated with the zonal circulation. Our measurements have been made in the wavelength range of 480-680 nm. Previously we successfully adapted this Doppler velocimetry technique for measuring winds at Venus cloud tops (Machado et al. 2012). In the present study we will show the adaptation of this method for Saturn's case. Since the AA technique only allows to compare spectra where the line shifts are within the line width, in fast rotating atmospheres (as is the case of Saturn) the spectra must be compared by pairs from adjacent areas of the disk (adjacent pixels in the slit). We will use coordinated observations from the Cassini's Visible and Infrared Mapping Spectrometer (VIMS), in order to compare with the Doppler winds obtained from the UVES/VLT

  7. VLT 8.2-m Unit Telescope no. 1 (as on September 7, 1995)

    Science.gov (United States)

    1995-09-01

    ESO Press Photos 28-30/95; 13 September 1995 The construction of the ESO Very Large Telescope (VLT) advances rapidly, both in Europe and in Chile. These three photos show some of the main mechanical parts of the first 8.2-metre telescope, as they presented themselves in Milan (Italy) on Thursday, September 7, 1995. Two versions of these photos, one smaller and one larger and with better image resolution, are accessible for convenient transfer over the networks. The mechanical structure of VLT Unit Telescope no. 1 is now in the process of being mounted at the Ansaldo Energia premises in Milan (Italy). The so-called main structure (i.e., telescope azimuth and altitude mechanical structure, including hydrostatic bearing system, direct drives and direct mounted encoding system) was designed and is being built by the Italian consortium AES, composed of Ansaldo Energia (Genova), SOIMI (Milan) and EIE (Venice). Already two months from now, in November 1995, the complete, enormous mechanical structures of this telescope will be moving on the azimuth hydrostatic bearing tracks, using the direct drive system designed and built by the PHASE Company (Genova, Italy). The thorough testing phase will start by the end of December 1995 or at the beginning of January 1996. ESO Press Photo 28/95 [54K] [248K] shows the lower part of the azimuth structure of the telescope (the fork) on the concrete pier on which the azimuth tracks (hydrostatic bearing journal) are mounted. The very high accuracy of this enormous structure (compare with the persons in the photo!) is illustrated by the fact that the "run-out" of the azimuth axis of the fork has been measured as only 80 microns (0.08 millimetres) on 90 degrees turning angle. This is a remarkable result, especially since the centering of the axis is done on a radial journal with a diameter of no less than 9 metres. When the fork is equipped with all auxiliary systems, it will weigh about 320 t, will be 18 metres long and 8 metres wide. It

  8. Mapping of Ozone on Mars at Infrared Wavelengths Using Crires at VLT

    Science.gov (United States)

    Radeva, Y. L.; Mumma, M. J.; Villanueva, G.; Novak, R.; Hartogh, P.; Encrenaz, T.; Kaufl, H.; Smette, A.

    2010-12-01

    We present spatially resolved maps of ozone and water on Mars, acquired on 21 August 2009 using the ultra-high resolution infrared spectrometer CRIRES at ESO’s VLT (Paranal, Chile). On Mars, the season was mid-summer in the South (Ls = 325) and the latitudinal resolution was 10 degrees FWHM at disk center. Ozone is produced by recombination of photochemically produced O and O2. It is destroyed by UV photolysis (with O2 (a1Dg) as a principal product) but also by reaction with odd hydrogen species (especially, H - a product of H2O vapor photolysis). Thus, simultaneous measurements of water and ozone can test this relationship. We quantified ozone using spectral lines (near 1.27 mm) of O2 (a1Dg). The emission from O2 (a1Dg) serves as a tracer for O3 above 20 km, since at lower altitudes collisions with CO2 quench the excited O2 (a1Dg) molecules. We confirmed the vertical location of the O2 (a1Dg) emission by extracting rotational temperatures from line-by-line ratios, and comparing them with standard vertical temperature profiles for this season and location(s). On the same night, we also obtained 2-D (lat-long) maps of Martian water from multiple H2O lines detected in the 3.3 mm region. We compare our retrieved distributions for ozone (latitude and altitude) with predictions of Lefevre et al. [I] based on their comprehensive 3-D circulation and photochemical model for the Martian atmosphere. Acknowledgements: This work was funded by NASA’s R&A Programs in Astrobiology (344-53-51), Planetary Astronomy (344-32-51-96), and Planetary Atmospheres (NNX09AB65G). We gratefully acknowledge the Director and staff of the European Southern Observatory, for supporting these observations. References: [I] Lefevre et al. (2004), J. of Geophys. Res. 109, E07004

  9. Spectral mapping of comet 67P/Churyumov-Gerasimenko with VLT/MUSE and SINFONI

    Science.gov (United States)

    Guilbert-Lepoutre, Aurelie; Besse, Sebastien; Snodgrass, Colin; Yang, Bin

    2016-10-01

    Comets are supposedly the most primitive objects in the solar system, preserving the earliest record of material from the nebula out of which our Sun and planets were formed, and thus holding crucial clues on the early phases of the solar system formation and evolution. For most small bodies in the solar system we can only access the surface properties, whereas active comet nuclei lose material from their subsurface, so that understanding cometary activity represents an unique opportunity to assess their internal composition, and by extension the composition, the temperature and pressure conditions of the protoplanetary disk at their place of formation.The ESA/Rosetta mission is performing the most thorough investigation of a comet ever made. Rosetta is measuring properties of comet 67P/Churyumov-Gerasimenko at distances between 5 and hundreds of km from the nucleus. However, it is unable to make any measurement over the thousands of km of the rest of the coma. Fortunately, the outer coma is accessible from the ground. In addition, we currently lack an understanding of how the very detailed information gathered from space-based observations can be extrapolated to the many ground-based observations that we can potentially perform. Combining parallel in situ observations with observations from the ground therefore gives us a great opportunity, not only to understand the behavior of 67P, but also to other comets observed exclusively from Earth. As part of the many observations taken from the ground, we have performed a spectral mapping of 67's coma using two IFU instruments mounted on the VLT: MUSE in the visible, and SINFONI in the near-infrared. The observations, carried out in March 2016, will be presented and discussed.

  10. Candle Flames in Microgravity: USML-1 Results - 1 Year Later

    Science.gov (United States)

    Ross, H. D.; Dietrich, D. L.; Tien, J. S.

    1994-01-01

    We report on the sustained behavior of a candle flame in microgravity determined in the glovebox facility aboard the First United States Microgravity Labomtofy. In a quiescent, microgmvjfy environment, diffusive transport becomes the dominant mode of heat and mass transfer; whether the diffusive transport rate is fast enough to sustain low-gravity candle flames in air was unknown to this series of about 70 tests. After an initial transient in which soot is observed, the microgravity candle flame in air becomes and remains hemispherical and blue (apparently soot-Ne) with a large flame standoff distance. Near flame extinction, spontaneous flame oscillations are regularly observed; these are explained as a flashback of flame through a premixed combustible gas followed by a retreat owed to flame quenching. The frequency of oscillations can be related to diffusive transport rates, and not to residual buoyant convective flow. The fact that the flame tip is the last point of the flame to survive suggests that it is the location of maximum fuel reactivity; this is unlike normal gravity, where the location of maximum fuel reactivity is the flame base. The flame color, size, and shape behaved in a quasi-steady manner; the finite size of the glovebox, combined with the restricted passages of the candlebox, inhibited the observation of true steady-state burning. Nonetheless, through calculations, and inference from the series of shuttle tests, if is concluded that a candle can burn indefinitely in a large enough ambient of air in microgravity. After igniting one candle, a second candle in close pximity could not be lit. This may be due to wax coating the wick and/or local oxygen depletion around the second, unlit candle. Post-mission testing suggests that simultaneous ignition may overcome these behaviors and enable both candles to be ignited.

  11. Structure of low-stretch methane nonpremixed flames

    Energy Technology Data Exchange (ETDEWEB)

    Han, Bai; Ibarreta, Alfonso F.; Sung, Chih-Jen; T' ien, James S. [Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106 (United States)

    2007-04-15

    The present study experimentally and numerically investigates the structure associated with extremely low-stretch ({proportional_to}2 s{sup -1}) gaseous nonpremixed flames. The study of low-stretch flames aims to improve our fundamental understanding of the flame radiation effects on flame response and extinction limits. Low-stretch flames are also relevant to fire safety in reduced-gravity environments and to large buoyant fires, where localized areas of low stretch are attainable. In this work, ultra-low-stretch flames are established in normal gravity by bottom burning of a methane/nitrogen mixture discharged from a porous spherically symmetric burner of large radius of curvature. The large thickness of the resulting nonpremixed flame allows detailed mapping of the flame structure. Several advanced nonintrusive optical diagnostics are used to study the flame structure. Gas phase temperatures are measured by Raman scattering, while the burner surface temperatures are obtained by IR imaging. In addition, OH-PLIF and chemiluminescence imaging techniques are used to help characterize the extent of the flame reaction zone. These experimental results allow direct comparison with a quasi-one-dimensional numerical model including detailed chemistry, thermodynamic/transport properties, and radiation treatment. In addition, the radiative interactions between the flame and porous burner (modeled as a gray surface) are accounted for in the present model. The numerical modeling is demonstrated to be able to simulate the low-stretch flame structure. Using the current model, the extinction limits under different conditions are also examined. The computational results are consistent with experimental observations. (author)

  12. FLAME MONITORING IN POWER STATION BOILERS USING IMAGE PROCESSING

    OpenAIRE

    K Sujatha; VENMATHI, M.; N. Pappa

    2012-01-01

    Combustion quality in power station boilers plays an important role in minimizing the flue gas emissions. In the present work various intelligent schemes to infer the flue gas emissions by monitoring the flame colour at the furnace of the boiler are proposed here. Flame image monitoring involves capturing the flame video over a period of time with the measurement of various parameters like Carbon dioxide (CO2), excess oxygen (O2), Nitrogen dioxide (NOx), Sulphur dioxide (SOx) and Carbon monox...

  13. Effect of Intense Sound Waves on a Stationary Gas Flame

    Science.gov (United States)

    Hahnemann, H; Ehret, L

    1950-01-01

    Intense sound waves with a resonant frequency of 5000 cycles per second were imposed on a stationary propane-air flame issuing from a nozzle. In addition to a slight increase of the flame velocity, a fundamental change both in the shape of the burning zone and in the flow pattern could be observed. An attempt is made to explain the origin of the variations in the flame configuration on the basis of transition at the nozzle from jet flow to potential flow.

  14. FIELD TEST OF THE FLAME QUALITY INDICATOR

    Energy Technology Data Exchange (ETDEWEB)

    Rudin, Andrew M; Butcher, Thomas; Troost, Henry

    2003-02-04

    The flame quality indicator concept was developed at BNL specifically to monitor the brightness of the flame in a small oil burner and to provide a ''call for service'' notification when the brightness has changed from its setpoint, either high or low. In prior development work BNL has explored the response of this system to operational upsets such as excess air changes, fouled atomizer nozzles, poor fuel quality, etc. Insight Technologies, Inc. and Honeywell, Inc. have licensed this technology from the U.S. Department of Energy and have been cooperating to develop product offerings which meet industry needs with an optimal combination of function and price. Honeywell has recently completed the development of the Flame Quality Monitor (FQM or Honeywell QS7100F). This is a small module which connects via a serial cable to the burners primary operating control. Primary advantages of this approach are simplicity, cost, and ease of installation. Call-for-service conditions are output in the form of front panel indicator lights and contact closure which can trigger a range of external communication options. Under this project a field test was conducted of the FQM in cooperation with service organizations in Virginia, Pennsylvania, New Jersey, New York, and Connecticut. At total of 83 field sites were included. At each site the FQM was installed in parallel with another embodiment of this concept--the Insight AFQI. The AFQI incorporates a modem and provides the ability to provide detailed information on the trends in the flame quality over the course of the two year test period. The test site population was comprised of 79.5% boilers, 13.7% warm air furnaces, and 6.8% water heaters. Nearly all were of residential size--with firing rates ranging from 0.6 gallons of oil per hour to 1.25. During the course of the test program the monitoring equipment successfully identified problems including: plugged fuel lines, fouled nozzles, collapsed combustion

  15. Research on Alkaline Filler Flame-Retarded Asphalt Pavement

    Institute of Scientific and Technical Information of China (English)

    HU Shuguang; ZHANG Houji; WANG Jiaolan

    2006-01-01

    Used as flame retardant of tunnel asphalt pavement, organic bromides produce a large amount of poisons and smoke in construction and flame retardation stage. The alkaline filler was found to replace mineral filler, and the flame-retarded asphalt mixtures were produced. Experimental results show that these asphalt mixtures are smoke restrained; the performances and construction technology of asphalt pavement are not influenced; also the alkaline filler is of low-price. So this kind of flame-retarded asphalt mixtures is suitable for tunnel pavement.

  16. Product engineering by high-temperature flame synthesis

    DEFF Research Database (Denmark)

    Johannessen, Tue; Johansen, Johnny; Mosleh, Majid;

    High-temperature flame processes can be applied as a tool for chemical product engineering. The general principle behind flame synthesis is the decomposition/oxidation of evaporated metal-precursors in a flame, thereby forming metal oxide monomers which nucleate, aggregate, and - to some extent...... product gas can be applied directly in additional product engineering concepts. A brief overview of on-going product developments and product engineering projects is outlined below. These projects, which are all founded on flame synthesis of nano-structured materials, include: • Preparation of catalyzed...

  17. Analytical Interaction of the Acoustic Wave and Turbulent Flame

    Institute of Scientific and Technical Information of China (English)

    TENG Hong-Hui; JIANG Zong-Lin

    2007-01-01

    A modified resonance model of a weakly turbulent flame in a high-frequency acoustic wave is derived analytically.Under the mechanism of Darrieus-Landau instability, the amplitude of flame wrinkles, which is as functions of turbulence. The high perturbation wave number makes the resonance easier to be triggered but weakened with respect to the extra acoustic wave. In a closed burning chamber with the acoustic wave induced by the flame itself, the high perturbation wave number is to restrain the resonance for a realistic flame.

  18. Measurement and Modeling of Particle Radiation in Coal Flames

    DEFF Research Database (Denmark)

    Bäckström, Daniel; Johansson, Robert; Andersson, Klas Jerker

    2014-01-01

    This work aims at developing a methodology that can provide information of in-flame particle radiation in industrial-scale flames. The method is based on a combination of experimental and modeling work. The experiments have been performed in the high-temperature zone of a 77 kWth swirling lignite...... properties. The in-flame particle radiation was measured with a Fourier transform infrared (FTIR) spectrometer connected to a water-cooled probe via fiber optics. In the cross-section of the flame investigated, the particles were found to be the dominating source of radiation. Apart from giving information...

  19. Modeling Burns for Pre-Cooled Skin Flame Exposure

    Directory of Open Access Journals (Sweden)

    Torgrim Log

    2017-09-01

    Full Text Available On a television show, a pre-cooled bare-skinned person (TV host passed through engulfing kerosene flames. The assumption was that a water film should protect him during 0.74 s flame exposure in an environment of 86 kW/m2 heat flux. The TV host got light burn inflammation on the back, arms and legs. The present work studies skin temperatures and burn damage integral of such dangerous flame exposure. The skin temperature distribution during water spray pre-cooling, transport to the flames, flame exposure, transport to the water pool, and final water pool cooling is modelled numerically. Details of the temperature development of the skin layers are presented, as well as the associated damage integral. It is shown that 5 °C water spray applied for a 30 s period pre-cooled the skin sufficiently to prevent severe skin injury. Soot marks indicate that the water layer evaporated completely in some areas resulting in skin flame contact. This exposed dry skin directly to the flames contributing significantly to the damage integral. It is further analyzed how higher water temperature, shorter pre-cooling period or longer flame exposure influence the damage integral. It is evident that minor changes in conditions could lead to severe burns and that high heat flux levels at the end of the exposure period are especially dangerous. This flame stunt should never be repeated.

  20. Flame dynamics in a micro-channeled combustor

    Science.gov (United States)

    Hussain, Taaha; Markides, Christos N.; Balachandran, Ramanarayanan

    2015-01-01

    The increasing use of Micro-Electro-Mechanical Systems (MEMS) has generated a significant interest in combustion-based power generation technologies, as a replacement of traditional electrochemical batteries which are plagued by low energy densities, short operational lives and low power-to-size and power-to-weight ratios. Moreover, the versatility of integrated combustion-based systems provides added scope for combined heat and power generation. This paper describes a study into the dynamics of premixed flames in a micro-channeled combustor. The details of the design and the geometry of the combustor are presented in the work by Kariuki and Balachandran [1]. This work showed that there were different modes of operation (periodic, a-periodic and stable), and that in the periodic mode the flame accelerated towards the injection manifold after entering the channels. The current study investigates these flames further. We will show that the flame enters the channel and propagates towards the injection manifold as a planar flame for a short distance, after which the flame shape and propagation is found to be chaotic in the middle section of the channel. Finally, the flame quenches when it reaches the injector slots. The glow plug position in the exhaust side ignites another flame, and the process repeats. It is found that an increase in air flow rate results in a considerable increase in the length (and associated time) over which the planar flame travels once it has entered a micro-channel, and a significant decrease in the time between its conversion into a chaotic flame and its extinction. It is well known from the literature that inside small channels the flame propagation is strongly influenced by the flow conditions and thermal management. An increase of the combustor block temperature at high flow rates has little effect on the flame lengths and times, whereas at low flow rates the time over which the planar flame front can be observed decreases and the time of

  1. Laser-induced fluorescence in high pressure solid propellant flames.

    Science.gov (United States)

    Edwards, T; Weaver, D P; Campbell, D H

    1987-09-01

    The application of laser-induced fluorescence (LIF) to the study of high pressure solid propellant flames is described. The distribution of the OH and CN radicals was determined in several solid propellant flames at pressures up to 3.5 MPa. The greatest difficulty in these measurements was the separation of the desired LIF signals from the large scattering at the laser wavelength from the very optically thick propellant flames. Raman experiments using 308-nm excitation were also attempted in the propellant flames but were unsuccessful due to LIF interferences from OH and NH.

  2. Flame fronts in Supernovae Ia and their pulsational stability

    CERN Document Server

    Glazyrin, S I; Dolgov, A D

    2013-01-01

    The structure of the deflagration burning front in type Ia supernovae is considered. The parameters of the flame are obtained: its normal velocity and thickness. The results are in good agreement with previous work of different authors. After that the question of pulsational instability of the flame subject to plane perturbations is considered. The flame can be unstable if hydrodynamics can be ignored, e.g. in solid-body propellants. However, with account of hydrodynamics we find that the flame in type Ia supernovae is pulsationally stable with realistic parameters of reactions and thermal conduction.

  3. Measurements of turbulent premixed flame dynamics using cinema stereoscopic PIV

    Energy Technology Data Exchange (ETDEWEB)

    Steinberg, Adam M.; Driscoll, James F. [University of Michigan, Department of Aerospace Engineering, Ann Arbor, MI (United States); Ceccio, Steven L. [University of Michigan, Department of Mechanical Engineering, Ann Arbor, MI (United States)

    2008-06-15

    A new experimental method is described that provides high-speed movies of turbulent premixed flame wrinkling dynamics and the associated vorticity fields. This method employs cinema stereoscopic particle image velocimetry and has been applied to a turbulent slot Bunsen flame. Three-component velocity fields were measured with high temporal and spatial resolutions of 0.9 ms and 140{mu}m, respectively. The flame-front location was determined using a new multi-step method based on particle image gradients, which is described. Comparisons are made between flame fronts found with this method and simultaneous CH-PLIF images. These show that the flame contour determined corresponds well to the true location of maximum gas density gradient. Time histories of typical eddy-flame interactions are reported and several important phenomena identified. Outwardly rotating eddy pairs wrinkle the flame and are attenuated at they pass through the flamelet. Significant flame-generated vorticity is produced downstream of the wrinkled tip. Similar wrinkles are caused by larger groups of outwardly rotating eddies. Inwardly rotating pairs cause significant convex wrinkles that grow as the flame propagates. These wrinkles encounter other eddies that alter their behavior. The effects of the hydrodynamic and diffusive instabilities are observed and found to be significant contributors to the formation and propagation of wrinkles. (orig.)

  4. TG-FTIR characterization of flame retardant polyurethane foams materials

    Science.gov (United States)

    Liu, W.; Tang, Y.; Li, F.; Ge, X. G.; Zhang, Z. J.

    2016-07-01

    Dimethyl methylphosphonate (DMMP) and trichloroethyl phosphtate (TCEP) have been used to enhance the flame retardancy of polyurethane foams materials (PUF). Flame retardancy and thermal degradation of PUF samples have been investigated by the LOI tests and thermal analysis. The results indicate that the excellent flame retardancy can be achieved due to the presence of the flame retardant system containing DMMP and TCEP. TG-FTIR reveals that the addition of DMMP/TCEP can not only improve the thermal stability of PUF samples but can also affect the gaseous phase at high temperature.

  5. POLYAMIDE 6 WITH A FLAME RETARDANT ENCAPSULATED BY POLYAMIDE 66: FLAME RETARDATION, THERMO-DECOMPOSITION AND THE POTENTIAL MECHANISM

    Institute of Scientific and Technical Information of China (English)

    Wei-cheng Xiong; Li Chen; Bin Zhao; De-yi Wang; Yu-zhong Wang

    2012-01-01

    A novel encapsulated flame retardant containing phosphorus-nitrogen (MSMM-Al-P) was prepared by encapsulating with polyamide 66 (PA66-MSMM-Al-P) for the flame retardation of polyamide 6 (PA6).The structure and thermal properties of PA66-MSMM-Al-P were characterized by Fourier-transform infrared spectroscopy,X-ray photoelectron spectroscopy and thermogravimetric analysis.The flammability of PA6 containing' flame retardants (MSMMAl-P and PA66-MSMM-Al-P) was investigated by the limiting oxygen index test,vertical burning test and cone calorimeter.The flame retardancy and cone calorimetric analyses suggested a synergistic effect between PA66 and MSMM-Al-P in the flame-retardant PA6.Thermal stability of the flame-retardant PA6 was also investigated.

  6. On-sky results of the adaptive optics MACAO for the new IR-spectrograph CRIRES at VLT

    CERN Document Server

    Paufique, J; Delabre, B; Donaldson, R; Esteves, R; Fedrigo, E; Gigan, P; Gojak, D; Hubin, N; Kasper, M; Kaeufl, U; Lizon, J L; Marchetti, E; Oberti, S; Pirard, J F; Pozna, E; Santos, J; Stroebele, S; Tordo, S; Lizon, JL.; Pirard, JF.

    2006-01-01

    The adaptive optics MACAO has been implemented in 6 focii of the VLT observatory, in three different flavors. We present in this paper the results obtained during the commissioning of the last of these units, MACAO-CRIRES. CRIRES is a high-resolution spectrograph, which efficiency will be improved by a factor two at least for point-sources observations with a NGS brighter than R=15. During the commissioning, Strehl exceeding 60% have been observed with fair seeing conditions, and a general description of the performance of this curvature adaptive optics system is done.

  7. The Stellar Mass Functions of the CLASH-VLT Clusters MACS J1206-0847 and Abell 209

    Science.gov (United States)

    Annunziatella, M.; Biviano, A.; Mercurio, A.; Nonino, M.; Rosati, P.; Balestra, I.; Girardi, M.; Grillo, C.

    The study of the galaxy stellar mass function, and in particular its dependence from the environment, represents a key observable to discriminate between different models of galaxy evolution. We determined the stellar mass function (SMF) of passive and star-forming (SF) galaxies in different regions of two clusters in the CLASH-VLT sample, MACS J1206.2-0847 and Abell 209. Since these two clusters are at different redshifts, the comparison between the results obtained in the two cases can inform us about the evolution of the SMF with cosmic time.

  8. VLT optical observations of V821 Ara(=GX339-4) in an extended "off" state

    CERN Document Server

    Shahbaz, T; Charles, P A

    2001-01-01

    We report on low-resolution spectroscopy of GX339-4 during its current, extended X-ray `off' state in May 2000 (r=20.1) obtained with the VLT Focal Reducer/low dispersion Spectrograph (FORS1). Although we do not positively detect the secondary star in GX339-4 we place an upper limit of 30 percent on the contribution of a ``normal'' K-type secondary star spectrum to the observed flux. Using this limit for the observed magnitude of the secondary star, we find a lower limit for the distance of GX339-4 to be 5.6 kpc.

  9. NGC 6302: high-ionization permitted lines. Applying X-SSN synthesis to VLT-UVES spectra

    CERN Document Server

    Pequignot, Daniel; Casassus, Simon

    2011-01-01

    A preliminary VLT-UVES spectrum of NGC 6302 (Casassus et al. 2002, MN), which hosts one of the hottest PN nuclei known (Teff ~ 220000 K; Wright et al. 2011, MN), has been recently analysed by means of X-SSN, a spectrum synthesis code for nebulae (Morisset and P\\'equignot). Permitted recombination lines from highly-ionized species are detected/identified for the first time in a PN, and some of them probably for the first time in (Astro)Physics. The need for a homogeneous, high signal-to-noise UVES spectrum for NGC 6302 is advocated.

  10. Investigations of two-phase flame propagation under microgravity conditions

    Science.gov (United States)

    Gokalp, Iskender

    2016-07-01

    Investigations of two-phase flame propagation under microgravity conditions R. Thimothée, C. Chauveau, F. Halter, I Gökalp Institut de Combustion, Aérothermique, Réactivité et Environnement (ICARE), CNRS, 1C Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France This paper presents and discusses recent results on two-phase flame propagation experiments we carried out with mono-sized ethanol droplet aerosols under microgravity conditions. Fundamental studies on the flame propagation in fuel droplet clouds or sprays are essential for a better understanding of the combustion processes in many practical applications including internal combustion engines for cars, modern aircraft and liquid rocket engines. Compared to homogeneous gas phase combustion, the presence of a liquid phase considerably complicates the physico-chemical processes that make up combustion phenomena by coupling liquid atomization, droplet vaporization, mixing and heterogeneous combustion processes giving rise to various combustion regimes where ignition problems and flame instabilities become crucial to understand and control. Almost all applications of spray combustion occur under high pressure conditions. When a high pressure two-phase flame propagation is investigated under normal gravity conditions, sedimentation effects and strong buoyancy flows complicate the picture by inducing additional phenomena and obscuring the proper effect of the presence of the liquid droplets on flame propagation compared to gas phase flame propagation. Conducting such experiments under reduced gravity conditions is therefore helpful for the fundamental understanding of two-phase combustion. We are considering spherically propagating two-phase flames where the fuel aerosol is generated from a gaseous air-fuel mixture using the condensation technique of expansion cooling, based on the Wilson cloud chamber principle. This technique is widely recognized to create well-defined mono-size droplets

  11. Nonpremixed flame in a counterflow under electric fields

    KAUST Repository

    Park, Daegeun

    2016-05-08

    Electrically assisted combustion has been studied in order to control or improve flame characteristics, and emphasizing efficiency and emission regulation. Many phenomenological observations have been reported on the positive impact of electric fields on flame, however there is a lack of detailed physical mechanisms for interpreting these. To clarify the effects of electric fields on flame, I have investigated flame structure, soot formation, and flow field with ionic wind electrical current responses in nonpremixed counterflow flames. The effects of direct current (DC) electric field on flame movement and flow field was also demonstrated in premixed Bunsen flames. When a DC electric field was applied to a lower nozzle, the flames moved toward the cathode side due to Lorentz force action on the positive ions, soot particles simultaneously disappeared completely and laser diagnostics was used to identify the results from the soot particles. To understand the effects of an electric field on flames, flow visualization was performed by Mie scattering to check the ionic wind effect, which is considered to play an important role in electric field assisted combustion. Results showed a bidirectional ionic wind, with a double-stagnant flow configuration, which blew from the flame (ionic source) toward both the cathode and the anode. This implies that the electric field affects strain rate and the axial location of stoichiometry, important factors in maintaining nonpremixed counterflow flames; thus, soot formation of the counterflow flame can also be affected by the electric field. In a test of premixed Bunsen flames having parallel electrodes, flame movement toward the cathode and bidirectional ionic wind were observed. Using PIV measurement it was found that a created radial velocity caused by positive ions (i.e. toward a cathode), was much faster than the velocity toward the anode. Even in a study of alternating current (AC) electric fields, bidirectional ionic wind could

  12. Extinction conditions of a premixed flame in a channel

    Energy Technology Data Exchange (ETDEWEB)

    Alliche, Mounir [LMP2M, Universite de Medea, Quartier Ain Dheb, 26000 Medea (Algeria); M2P2, UMR CNRS 6181, Universite de Provence, Marseille (France); Haldenwang, Pierre [M2P2, UMR CNRS 6181, Universite de Provence, Marseille (France); Chikh, Salah [LTPMP, Faculte de Genie Mecanique and de Genie des Procedes, USTHB, Bab Ezzouar (Algeria)

    2010-06-15

    A local refinement method is used to numerically predict the propagation and extinction conditions of a premixed flame in a channel considering a thermodiffusive model. A local refinement method is employed because of the numerous length scales that characterize this phenomenon. The time integration is self adaptive and the solution is based on a multigrid method using a zonal mesh refinement in the flame reaction zone. The objective is to determine the conditions of extinction which are characterized by the flame structure and its properties. We are interested in the following properties: the curvature of the flame, its maximum temperature, its speed of propagation and the distance separating the flame from the wall. We analyze the influence of heat losses at the wall through the thermal conductivity of the wall and the nature of the fuel characterized by the Lewis number of the mixture. This investigation allows us to identify three propagation regimes according to heat losses at the wall and to the channel radius. The results show that there is an intermediate value of the radius for which the flame can bend and propagate provided that its curvature does not exceed a certain limit value. Indeed, small values of the radius will choke the flame and extinguish it. The extinction occurs if the flame curvature becomes too small. Furthermore, this study allows us to predict the limiting values of the heat loss coefficient at extinction as well as the critical value of the channel radius above which the premixed flame may propagate without extinction. A dead zone of length 2-4 times the flame thickness appears between the flame and the wall for a Lewis number (Le) between 0.8 and 2. For small values of Le, local extinctions are observed. (author)

  13. Using fear appeals in warning labels to promote responsible gambling among VLT players: the key role of depth of information processing.

    Science.gov (United States)

    Munoz, Yaromir; Chebat, Jean-Charles; Suissa, Jacob Amnon

    2010-12-01

    Video lottery terminals (VLT) are a highly lucrative gambling format, but at the same time they are among the most hazardous. Previous research has shown that threatening warnings may be an appropriate approach for promoting protective behavior. The present study explores the potential benefits of threatening warnings in the fight against compulsive gambling. A 4 × 2 factorial design experiment was used to test our model based on both Elaboration Likelihood Model and Protection Motivation Theory. 258 VLT adult players (58% males, 42% females) with various degrees of problem gambling were exposed to three threat levels (plus a control condition) from two different sources (i.e., either a medical source or a source related to the provider of VLT's). Our results show that both higher threat warnings and the medical source of warnings enhance Depth of Information Processing. It was also found that Depth of Information Processing affects positively attitude change and compliance intentions. The theoretical and managerial implications are discussed.

  14. Hubble Tarantula Treasury Project. III. Photometric Catalog and Resulting Constraints on the Progression of Star Formation in the 30 Doradus Region

    Science.gov (United States)

    Sabbi, E.; Lennon, D. J.; Anderson, J.; Cignoni, M.; van der Marel, R. P.; Zaritsky, D.; De Marchi, G.; Panagia, N.; Gouliermis, D. A.; Grebel, E. K.; Gallagher, J. S., III; Smith, L. J.; Sana, H.; Aloisi, A.; Tosi, M.; Evans, C. J.; Arab, H.; Boyer, M.; de Mink, S. E.; Gordon, K.; Koekemoer, A. M.; Larsen, S. S.; Ryon, J. E.; Zeidler, P.

    2016-01-01

    We present and describe the astro-photometric catalog of more than 800,000 sources found in the Hubble Tarantula Treasury Project (HTTP). HTTP is a Hubble Space Telescope Treasury program designed to image the entire 30 Doradus region down to the sub-solar (˜0.5 M⊙) mass regime using the Wide Field Camera 3 and the Advanced Camera for Surveys. We observed 30 Doradus in the near-ultraviolet (F275W, F336W), optical (F555W, F658N, F775W), and near-infrared (F110W, F160W) wavelengths. The stellar photometry was measured using point-spread function fitting across all bands simultaneously. The relative astrometric accuracy of the catalog is 0.4 mas. The astro-photometric catalog, results from artificial star experiments, and the mosaics for all the filters are available for download. Color-magnitude diagrams are presented showing the spatial distributions and ages of stars within 30 Dor as well as in the surrounding fields. HTTP provides the first rich and statistically significant sample of intermediate- and low-mass pre-main sequence candidates and allows us to trace how star formation has been developing through the region. The depth and high spatial resolution of our analysis highlight the dual role of stellar feedback in quenching and triggering star formation on the giant H ii region scale. Our results are consistent with stellar sub-clustering in a partially filled gaseous nebula that is offset toward our side of the Large Magellanic Cloud. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555.

  15. Three Peptide Modulators of the Human Voltage-Gated Sodium Channel 1.7, an Important Analgesic Target, from the Venom of an Australian Tarantula

    Directory of Open Access Journals (Sweden)

    Chun Yuen Chow

    2015-06-01

    Full Text Available Voltage-gated sodium (NaV channels are responsible for propagating action potentials in excitable cells. NaV1.7 plays a crucial role in the human pain signalling pathway and it is an important therapeutic target for treatment of chronic pain. Numerous spider venom peptides have been shown to modulate the activity of NaV channels and these peptides represent a rich source of research tools and therapeutic lead molecules. The aim of this study was to determine the diversity of NaV1.7-active peptides in the venom of an Australian Phlogius sp. tarantula and to characterise their potency and subtype selectivity. We isolated three novel peptides, μ-TRTX-Phlo1a, -Phlo1b and -Phlo2a, that inhibit human NaV1.7 (hNaV1.7. Phlo1a and Phlo1b are 35-residue peptides that differ by one amino acid and belong in NaSpTx family 2. The partial sequence of Phlo2a revealed extensive similarity with ProTx-II from NaSpTx family 3. Phlo1a and Phlo1b inhibit hNaV1.7 with IC50 values of 459 and 360 nM, respectively, with only minor inhibitory activity on rat NaV1.2 and hNaV1.5. Although similarly potent at hNaV1.7 (IC50 333 nM, Phlo2a was less selective, as it also potently inhibited rNaV1.2 and hNaV1.5. All three peptides cause a depolarising shift in the voltage-dependence of hNaV1.7 activation.

  16. HUBBLE TARANTULA TREASURY PROJECT. III. PHOTOMETRIC CATALOG AND RESULTING CONSTRAINTS ON THE PROGRESSION OF STAR FORMATION IN THE 30 DORADUS REGION

    Energy Technology Data Exchange (ETDEWEB)

    Sabbi, E.; Anderson, J.; Cignoni, M.; Marel, R. P. van der; Panagia, N.; Sana, H.; Aloisi, A.; Arab, H.; Gordon, K. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, 21218 (United States); Lennon, D. J. [ESA—European Space Astronomy Center, Apdo. de Correo 78, E-28691 Associate Villanueva de la Cañada, Madrid (Spain); Zaritsky, D. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Marchi, G. De [Space Science Department, European Space Agency, Keplerlaan 1, 2200 AG Noordwijk (Netherlands); Gouliermis, D. A. [Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Grebel, E. K. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany); III, J. S. Gallagher [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Smith, L. J. [ESA/STScI, 3700 San Martin Drive, Baltimore, MD, 21218 (United States); Tosi, M. [Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Evans, C. J. [UK Astronomy Technology Center, Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom); Boyer, M. [Observational Cosmology Lab, Code 665, NASA, Goddard Space Flight Center, Greenbelt, MD, 20771 (United States); Mink, S. E. de, E-mail: sabbi@stsci.edu [Astronomical Institute “Anton Pannekoek,”University of Amsterdam, P.O. Box 94249, NL-1090 GE Amsterdam (Netherlands); and others

    2016-01-15

    We present and describe the astro-photometric catalog of more than 800,000 sources found in the Hubble Tarantula Treasury Project (HTTP). HTTP is a Hubble Space Telescope Treasury program designed to image the entire 30 Doradus region down to the sub-solar (∼0.5 M{sub ⊙}) mass regime using the Wide Field Camera 3 and the Advanced Camera for Surveys. We observed 30 Doradus in the near-ultraviolet (F275W, F336W), optical (F555W, F658N, F775W), and near-infrared (F110W, F160W) wavelengths. The stellar photometry was measured using point-spread function fitting across all bands simultaneously. The relative astrometric accuracy of the catalog is 0.4 mas. The astro-photometric catalog, results from artificial star experiments, and the mosaics for all the filters are available for download. Color–magnitude diagrams are presented showing the spatial distributions and ages of stars within 30 Dor as well as in the surrounding fields. HTTP provides the first rich and statistically significant sample of intermediate- and low-mass pre-main sequence candidates and allows us to trace how star formation has been developing through the region. The depth and high spatial resolution of our analysis highlight the dual role of stellar feedback in quenching and triggering star formation on the giant H ii region scale. Our results are consistent with stellar sub-clustering in a partially filled gaseous nebula that is offset toward our side of the Large Magellanic Cloud.

  17. Effect of Flame Conditions on Crystalline Structure of TiO2 in Liquid Flame Spraying

    Institute of Scientific and Technical Information of China (English)

    LI Chang-jiu; YANG Guan-jun; WANG Yu-yue

    2004-01-01

    Nanostructured TiO2 is a most promising functional ceramic owing to its potential utilization in photocatalytical, optical and electrical applications. Nanostructured TiO2 coating was deposited through thermal spraying with liquid feedstock. Two types of crystalline structures were present in the synthesized TiO2 coating including anatase phase and rutile phase.The effect of spray flame conditions on the crystalline structure was investigated in order to control the crystalline structure of the coating. The results showed that spray distance, flame power and precursor concentration in the liquid feedstock significantly influenced phase constitutions and grain size in the coating. Anatase phase was formed at spray distance from 150 to 250mm, while rutile phase was evidently observed in the coating deposited at 100 mm. The results suggested that anatase phase was firstly formed in the coating, and rutile phase resulted from the transformation of the deposited anatase phase. The phase transformation from anatase to rutile occurred through the annealing effect of spraying flame. The control of the phase formation can be realized through flame condition and spray distance.

  18. In-Flame Characterization of a 30 MWth Bio-Dust Flame

    DEFF Research Database (Denmark)

    Johansen, Joakim Myung; Jensen, Peter Arendt; Clausen, Sønnik

    This work presents a comprehensive flame characterization campaign on an operating full-scale Danish power plant. Amagerværket Unit 1 (AMV1, 350 MWth, 12 identical burners on 3 burner levels) is 100 % fuelled with wood dust burned in suspension and stabilized by swirling flows in a triple concent...

  19. In-Flame Characterization of a 30 MWth Bio-Dust Flame

    DEFF Research Database (Denmark)

    Johansen, Joakim Myung; Jensen, Peter Arendt; Clausen, Sønnik;

    This work presents a comprehensive flame characterization campaign on an operating full-scale Danish power plant. Amagerværket Unit 1 (AMV1, 350 MWth, 12 identical burners on 3 burner levels) is 100 % fuelled with wood dust burned in suspension and stabilized by swirling flows in a triple...

  20. CLASH-VLT: testing the nature of gravity with galaxy cluster mass profiles

    Science.gov (United States)

    Pizzuti, L.; Sartoris, B.; Borgani, S.; Amendola, L.; Umetsu, K.; Biviano, A.; Girardi, M.; Rosati, P.; Balestra, I.; Caminha, G. B.; Frye, B.; Koekemoer, A.; Grillo, C.; Lombardi, M.; Mercurio, A.; Nonino, M.

    2016-04-01

    We use high-precision kinematic and lensing measurements of the total mass profile of the dynamically relaxed galaxy cluster MACS J1206.2-0847 at z=0.44 to estimate the value of the ratio η=Ψ/Φ between the two scalar potentials in the linear perturbed Friedmann-Lemaitre-Robertson-Walker metric. An accurate measurement of this ratio, called anisotropic stress, could show possible, interesting deviations from the predictions of the theory of General Relativity, according to which Ψ should be equal to Φ. Complementary kinematic and lensing mass profiles were derived from exhaustive analyses using the data from the Cluster Lensing And Supernova survey with Hubble (CLASH) and the spectroscopic follow-up with the Very Large Telescope (CLASH-VLT). Whereas the kinematic mass profile tracks only the time-time part of the perturbed metric (i.e. only Φ), the lensing mass profile reflects the contribution of both time-time and space-space components (i.e. the sum Φ+Ψ). We thus express η as a function of the mass profiles and perform our analysis over the radial range 0.5 MpcFrenk-White mass profile, which well fits the data, we obtain η(r200)=1.01 -0.28+0.31 at the 68% C.L. We discuss the effect of assuming different functional forms for mass profiles and of the orbit anisotropy in the kinematic reconstruction. Interpreting this result within the well-studied f(R) modified gravity model, the constraint on η translates into an upper bound to the interaction length (inverse of the scalaron mass) smaller than 2 Mpc. This tight constraint on the f(R) interaction range is however substantially relaxed when systematic uncertainties in the analysis are considered. Our analysis highlights the potential of this method to detect deviations from general relativity, while calling for the need of further high-quality data on the total mass distribution of clusters and improved control on systematic effects.

  1. Nanotechnology finding its way into flame retardancy

    Energy Technology Data Exchange (ETDEWEB)

    Schartel, Bernhard, E-mail: bernhard.schartel@bam.de [BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin (Germany)

    2014-05-15

    Nanotechnology is one of the key technologies of the 21{sup st} century. The exploitation of 'new' effects that arise from materials structured on the nano-scale has also been proposed successfully for flame retardancy of polymers since the end of the 90s. Of all of the approaches these include, at this time the use of nanocomposites offers the best potential for industrial application, also some other ideas are sketched, such as using electrospun nanofibers mats or layer-by-layer deposits as protection coatings, as well as sub-micrometer multilayer coatings as effective IR-mirrors. The general phenomena, inducing a flow limit in the pyrolysing melt and changing the fire residue, are identified in nanocomposites. Key experiments are performed such as quasi online investigation of the protection layer formation to understand what is going on in detail. The flame retardancy mechanisms are discussed and their impact on fire behaviour quantified. With the latter, the presentation pushes forward the state of the art. For instance, the heat shielding is experimentally quantified for a layered silicate epoxy resin nanocomposite proving that it is the only import mechanism controlling the reduction in peak heat release rate in the investigated system for different irradiations. The flame retardancy performance is assessed comprehensively illuminating not only the strengths but also the weak points of the concepts. Guidelines for materials development are deduced and discussed. Apart from inorganic fillers (layered silicate, boehmite, etc.) not only carbon nanoobjects such as multiwall carbon nanotubes, multilayer graphene and graphene are investigated, but also nanoparticles that are more reactive and harbor the potential for more beneficial interactions with the polymer matrix.

  2. Atmospheric Pressure Plasma Based Flame Control and Diagnostics

    Science.gov (United States)

    2015-01-01

    TYPE 3. DATES COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE Atmospheric Pressure Plasma Based Flame Control and Diagnostics 5a...to 10%)  Flame speed enhancement (>20%)  Extension of lean limit (factor of two)  Distributed ignition  Development of new diagnostics

  3. 30 CFR 75.600 - Trailing cables; flame resistance.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Trailing cables; flame resistance. 75.600 Section 75.600 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE... cables; flame resistance. Trailing cables used in coal mines shall meet the requirements established...

  4. Camping Burner-Based Flame Emission Spectrometer for Classroom Demonstrations

    Science.gov (United States)

    Ne´el, Bastien; Crespo, Gasto´n A.; Perret, Didier; Cherubini, Thomas; Bakker, Eric

    2014-01-01

    A flame emission spectrometer was built in-house for the purpose of introducing this analytical technique to students at the high school level. The aqueous sample is sprayed through a homemade nebulizer into the air inlet of a consumer-grade propane camping burner. The resulting flame is analyzed by a commercial array spectrometer for the visible…

  5. 46 CFR 151.03-25 - Flame screen.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Flame screen. 151.03-25 Section 151.03-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES BARGES CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Definitions § 151.03-25 Flame screen. A fitted single screen...

  6. Aspects of Cool-Flame Supported Droplet Combustion in Microgravity

    Science.gov (United States)

    Nayagam, Vedha; Dietrich, Daniel L.; Williams, Forman A.

    2015-01-01

    Droplet combustion experiments performed on board the International Space Station have shown that normal-alkane fuels with negative temperature coefficient (NTC) chemistry can support quasi-steady, low-temperature combustion without any visible flame. Here we review the results for n-decane, n-heptane, and n-octane droplets burning in carbon dioxidehelium diluted environments at different pressures and initial droplet sizes. Experimental results for cool-flame burning rates, flame standoff ratios, and extinction diameters are compared against simplified theoretical models of the phenomenon. A simplified quasi-steady model based on the partial-burning regime of Lin predicts the burning rate, and flame standoff ratio reasonably well for all three normal alkanes. The second-stage cool-flame burning and extinction following the first-stage hot-flame combustion, however, shows a small dependence on the initial droplet size, thus deviating from the quasi-steady results. An asymptotic model that estimates the oxygen depletion by the hot flame and its influence on cool-flame burning rates is shown to correct the quasi-steady results and provide a better comparison with the measured burning-rate results.This work was supported by the NASA Space Life and Physical Sciences Research and Applications Program and the International Space Station Program.

  7. 49 CFR 195.438 - Smoking or open flames.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Smoking or open flames. 195.438 Section 195.438 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Operation and Maintenance § 195.438 Smoking or open flames. Each operator shall prohibit...

  8. 30 CFR 57.6904 - Smoking and open flames.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Smoking and open flames. 57.6904 Section 57.6904 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL... General Requirements-Surface and Underground § 57.6904 Smoking and open flames. Smoking and use of...

  9. Laminar dust flames in a reduced-gravity environment

    Science.gov (United States)

    Goroshin, Samuel; Tang, Francois-David; Higgins, Andrew J.; Lee, John H. S.

    2011-04-01

    The propagation of laminar dust flames in suspensions of iron in gaseous oxidizers was studied in a low-gravity environment onboard a parabolic flight aircraft. The reduction of buoyancy-induced convective flows and particle settling permitted the measurement of fundamental combustion parameters, such as the burning velocity and the flame quenching distance over a wide range of particle sizes and in different gaseous mixtures. Experimentally measured flame speeds and quenching distances were found in good agreement with theoretical predictions of a simplified analytical model that assumes particles burning in a diffusive mode. However, the comparison of flame speeds in oxygen-argon and oxygen-helium iron suspensions indicates the possibility that fine micron-sized particles burn in the kinetic mode. Furthermore, when the particle spacing is large compared to the scale of the reaction zone, a theoretical analysis suggests the existence of a new so-called discrete flame propagation regime. Discrete flames are strongly dependent on particle density fluctuations and demonstrate directed percolation behavior near flame propagation limits. The experimental observation of discrete flames in particle suspensions will require low levels of gravity over extended periods available only on orbital platforms.

  10. Toxicity of new generation flame retardants to Daphnia magna

    NARCIS (Netherlands)

    Waaijers, S.L.; Hartmann, J; Soeter, A.M.; Helmus, R.; Kools, S.A.E.; de Voogt, P.; Admiraal, W.; Parsons, J.R.; Kraak, M.H.S.

    2013-01-01

    There is a tendency to substitute frequently used, but relatively hazardous brominated flame retardants (BFRs) with halogen-free flame retardants (HFFRs). Consequently, information on the persistence, bioaccumulation and toxicity (PBT) of these HFFRs is urgently needed, but large data gaps and

  11. Characteristics of premixed, laminar CO/N2O flames

    NARCIS (Netherlands)

    Kalff, P.J.; Alkemade, C.T.J.

    1972-01-01

    Several properties are studied of fuel-rich (CO:N2O = 1.5:1) and stoichiometrie (CO:N2O = 1:1) carbon monoxide/nitrous oxide flames with varying water content up to 10%. Flame temperatures, ranging from 2680 to 2860°K. are measured with the line-reversal method, and compared with calculated adiabati

  12. FIBRED MAGNESIUM HYDROXIDE AND FLAME-RESISTANT POLYENE MATERIAL

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The fibred mangesiun hydroxide from the bracite was treated with a surface active agent. The modified fibred magesium hydroxide as f lame-retardant,boric acid, barium stearate, polydimethyl siloxane fluid,vinyltr iethoxysilane as synergists of the flame-retardant were added to polyene resin. The flame-resistance polyene material prepared meets the requirements of EWCZ -6287-1.

  13. An investigation of streaklike instabilities in laminar boundary layer flames

    Science.gov (United States)

    Miller, Colin; Finney, Mark; Forthofer, Jason; McAllister, Sara; Gollner, Michael

    2016-11-01

    Observations of coherent structures in boundary layer flames, particularly wildland fires, motivated an investigation on flame instabilities within a boundary layer. This experimental study examined streaklike structures in a stationary diffusion flame stabilized within a laminar boundary layer. Flame streaks were found to align with pre-existing velocity perturbations, enabling stabilization of these coherent structures. Thermocouple measurements were used to quantify streamwise amplification of flame streaks. Temperature mapping indicated a temperature rise in the flame streaks, while the region in between these streaks, the trough, decreased in temperature. The heat flux to the surface was measured with a total heat flux gauge, and the heat flux below the troughs was found to be higher at all measurement locations. This was likely a function of the flame standoff distance, and indicated that the flame streaks were acting to modify the spanwise distribution of heat flux. Instabilities in boundary layer combustion can have an effect on the spanwise distribution of heat transfer. This finding has significant implications for boundary layer combustion, indicating that instantaneous properties can vary significantly in a three-dimensional flow field.

  14. Soot Formation in Freely-Propagating Laminar Premixed Flames

    Science.gov (United States)

    Lin, K.-C.; Hassan, M. I.; Faeth, G. M.

    1997-01-01

    Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science. Thus, the present study is considering soot formation in freely-propagating laminar premixed flames, exploiting the microgravity environment to simplify measurements at the high-pressure conditions of interest for many practical applications. The findings of the investigation are relevant to reducing emissions of soot and continuum radiation from combustion processes, to improving terrestrial and spacecraft fire safety, and to developing methods of computational combustion, among others. Laminar premixed flames are attractive for studying soot formation because they are simple one-dimensional flows that are computationally tractable for detailed numerical simulations. Nevertheless, studying soot-containing burner-stabilized laminar premixed flames is problematical: spatial resolution and residence times are limited at the pressures of interest for practical applications, flame structure is sensitive to minor burner construction details so that experimental reproducibility is not very good, consistent burner behavior over the lengthy test programs needed to measure soot formation properties is hard to achieve, and burners have poor durability. Fortunately, many of these problems are mitigated for soot-containing, freely-propagating laminar premixed flames. The present investigation seeks to extend work in this laboratory for various soot processes in flames by observing soot formation in freely-propagating laminar premixed flames. Measurements are being made at both Normal Gravity (NG) and MicroGravity (MG), using a short-drop free-fall facility to provide MG conditions.

  15. Reconstructing the Cryptanalytic Attack behind the Flame Malware

    NARCIS (Netherlands)

    Fillinger, M.J.

    2013-01-01

    Flame was an advanced malware, used for espionage, which infected computers running a Microsoft Windows operating system. Once a computer in a local network was infected, Flame could spread to the other computers in the network via Windows Update, disguised as a security patch from Microsoft. Window

  16. Oxyhydrogen burner for low-temperature flame fusion

    Science.gov (United States)

    Ueltzen, M.; Brüggenkamp, T.; Franke, M.; Altenburg, H.

    1993-04-01

    An oxyhydrogen burner as described in this article enables the growth of crystals by Verneuil's technique at temperatures of about 1000 °C. The powder fed to the crystal passes along a low-temperature pathway through the flame, so that evaporation of volatile components is prevented. Low-temperature flame fusion of superconducting Y-Ba-cuprate is reported.

  17. The Great Observatories Origins Deep Survey VLT/FORS2 Spectroscopy in the GOODS-South Field: Part II

    CERN Document Server

    Vanzella, E; Dickinson, M; Kuntschner, H; Nonino, M; Rettura, A; Rosati, P; Vernet, J; Césarsky, C J; Ferguson, H C; Fosbury, R A E; Giavalisco, M; Haase, J; Moustakas, L A; Popesso, P; Renzini, A; Stern, D; Team, the GOODS

    2006-01-01

    We present the second campaign of the ESO/GOODS program of spectroscopy of faint galaxies in the Chandra Deep Field South (CDF-S). Objects were selected as candidates for VLT/FORS2 observations primarily based on the expectation that the detection and measurement of their spectral features would benefit from the high throughput and spectral resolution of FORS2. The reliability of the redshift estimates is assessed using diagnostic diagrams and comparing the results with public data. 807 spectra of 652 individual targets have been obtained in service mode with the FORS2 spectrograph at the ESO/VLT, providing 501 redshift determinations. The typical redshift uncertainty is estimated to be sigma_z ~ 0.0009. Galaxies have been color selected in a way that the resulting redshift distribution typically spans two redshift domains: from z=0.5 to 2 and z=3.5 to 6.2. In particular, 94 B435-,V606-,i775-"dropout" Lyman break galaxies have been observed, yielding redshifts for 64 objects in the interval 3.4

  18. CLASH-VLT: Substructure in the galaxy cluster MACS J1206.2-0847 from kinematics of galaxy populations

    CERN Document Server

    Girardi, M; Balestra, I; Nonino, M; Biviano, A; Grillo, C; Rosati, P; Annunziatella, M; Demarco, R; Fritz, A; Gobat, R; Lemze, D; Presotto, V; Scodeggio, M; Tozzi, P; Caminha, G Bartosch; Brescia, M; Coe, D; Kelson, D; Koekemoer, A; Lombardi, M; Medezinski, E; Postman, M; Sartoris, B; Umetsu, K; Zitrin, A; Boschin, W; Czoske, O; De Lucia, G; Kuchner, U; Maier, C; Meneghetti, M; Monaco, P; Monna, A; Munari, E; Seitz, S; Verdugo, M; Ziegler, B

    2015-01-01

    In the effort to understand the link between the structure of galaxy clusters and their galaxy populations, we focus on MACS J1206.2-0847, at z~0.44, probing its substructure in the projected phase space through the spectrophotometric properties of a large number of galaxies from the CLASH-VLT survey. Our analysis is mainly based on an extensive spectroscopic dataset of 445 member galaxies, mostly acquired with VIMOS@VLT as part of our ESO Large Programme, sampling the cluster out to a radius ~2R200 (4 Mpc). We classify 412 galaxies as: passive, with strong Hdelta absorption (red and blue ones), and with emission lines from weak to very strong ones. A number of tests for substructure detection is applied to analyze the galaxy distribution in the velocity space, in the 2D space, and in the (3D) projected phase-space. Studied in its entirety, the cluster appears as a large-scale relaxed system with a few, secondary, minor overdensities in 2D distribution. We detect no velocity gradient or evidence of deviations...

  19. Is Fear to Intervene with Problem Gamblers Related to Interveners' Gender and Status? A Study with VLT Operators.

    Science.gov (United States)

    Tomei, Alexander; Zumwald, Coralie

    2017-03-01

    We assess how video lottery terminal (VLT) operators' self-perceive their ability to recognize a problem gambler, to what extent they are approached by problem gamblers seeking for assistance, how many detections and interventions they report, and the reasons they give for not intervening with clients who show signs of problem gambling. We also examine how these variables are related to the operators' gender and status in the establishment. 177 VLT operators anonymously completed a structured questionnaire at the beginning of a responsible gambling training class held in different French-speaking Swiss towns. The operators felt confident in their ability to detect problem gambling behaviors, were rarely approached by problem gamblers seeking assistance, and reported fewer interventions compared to the number of detections. This reluctance to intervene was mainly attributed to the fear of potential negative reactions from the client. Female staff were the most reluctant to intervene and the most fearful of potential negative reactions from the client. Responsible gambling training programs should include coping strategies for dealing with potential negative reactions from clients. Our findings suggest that staff gender and status are two individual characteristics that should be taken into account when planning responsible gambling trainings.

  20. The VLT observations of the HDF-S NICMOS field photometric catalog and high redshift galaxy candidates

    CERN Document Server

    Fontana, A; Fosbury, R A E; Giallongo, E; Hook, R N; Poli, F; Renzini, A; Rosati, P; Viezzer, R

    1999-01-01

    We present the deep UBVRI observations of the HDF-S NICMOS field obtained as part of the Science Verification of the VLT Unit 1 telescope. The images have been used to construct object catalogs and to obtain photometric redshifts. The effective field of view is $\\simeq 70\\times70$ arcsec$^2$, and the formal $5\\sigma$ limiting magnitudes (in a 2 FWHM aperture) are 26.3, 27.8, 27.5, 26.9, 25.2 in the $U$, $B$, $V$, $R$ and $I$ bands, respectively. Thanks to the sub-arcsecond image quality, relatively long exposure time, and large collecting area of the VLT, this is the deepest set of multicolor images ever obtained from a ground-based telescope. Galaxy counts have been derived independently in each band, and show no significant departures from previous data from wider areas. A multicolor photometric catalog of all the galaxies selected in the $R$ band has also been obtained and used to derive photometric redshifts for all galaxies with $R \\leq 26.5 $, using also the J,H and K magnitudes from the NICMOS deep obs...