The Experts below are selected from a list of 5322 Experts worldwide ranked by ideXlab platform
Katherine I Lee - One of the best experts on this subject based on the ideXlab platform.
-
carma large area star formation survey structure and kinematics of dense gas in serpens main
The Astrophysical Journal, 2014Co-Authors: Katherine I Lee, Manuel Fernandezlopez, Shaye Storm, Leslie W Looney, Lee G Mundy, Dominique Seguracox, Peter Teuben, Erik RosolowskyAbstract:We present observations of NL_2H^+ (J = 1 -> 0), HCO^+ (J = 1 -> 0), and HCN (J = 1 -> 0) toward the Serpens Main molecular cloud from the CARMA Large Area Star Formation Survey (CLASSy). We mapped 150 arcmin(2) of Serpens Main with an angular resolution of ~7". The gas emission is concentrated in two Subclusters (the NW and SE Subclusters). The SE subcluster has more prominent filamentary structures and more complicated kinematics compared to the NW subcluster. The majority of gas in the two Subclusters has subsonic to sonic velocity dispersions. We applied a dendrogram technique with N_2H^+(1-0) to study the gas structures; the SE subcluster has a higher degree of hierarchy than the NW subcluster. Combining the dendrogram and line fitting analyses reveals two distinct relations: a flat relation between nonthermal velocity dispersion and size, and a positive correlation between variation in velocity centroids and size. The two relations imply a characteristic depth of 0.15 pc for the cloud. Furthermore, we have identified six filaments in the SE subcluster. These filaments have lengths of ~0.2 pc and widths of ~0.03 pc, which is smaller than a characteristic width of 0.1 pc suggested by Herschel observations. The filaments can be classified into two types based on their properties. The first type, located in the northeast of the SE subcluster, has larger velocity gradients, smaller masses, and nearly critical mass-per-unit-length ratios. The other type, located in the southwest of the SE subcluster, has the opposite properties. Several YSOs are formed along two filaments which have supercritical mass per unit length ratios, while filaments with nearly critical massper- unit-length ratios are not associated with YSOs, suggesting that stars are formed on gravitationally unstable filaments.
-
carma large area star formation survey structure and kinematics of dense gas in serpens main
arXiv: Astrophysics of Galaxies, 2014Co-Authors: Katherine I Lee, Manuel Fernandezlopez, Shaye Storm, Leslie W Looney, Lee G Mundy, Dominique Seguracox, Peter Teuben, Erik RosolowskyAbstract:We present observations of N2H+(1-0), HCO+(1-0), and HCN(1-0) toward the Serpens Main molecular cloud from the CARMA Large Area Star Formation Survey (CLASSy). We mapped 150 square arcminutes of Serpens Main with an angular resolution of 7 arcsecs. The gas emission is concentrated in two Subclusters (the NW and SE Subclusters). The SE subcluster has more prominent filamentary structures and more complicated kinematics compared to the NW subcluster. The majority of gas in the two Subclusters has subsonic to sonic velocity dispersions. We applied a dendrogram technique with N2H+(1-0) to study the gas structures; the SE subcluster has a higher degree of hierarchy than the NW subcluster. Combining the dendrogram and line fitting analyses reveals two distinct relations: a flat relation between nonthermal velocity dispersion and size, and a positive correlation between variation in velocity centroids and size. The two relations imply a characteristic depth of 0.15 pc for the cloud. Furthermore, we have identified six filaments in the SE subcluster. These filaments have lengths of 0.2 pc and widths of 0.03 pc, which is smaller than a characteristic width of 0.1 pc suggested by Herschel observations. The filaments can be classified into two types based on their properties. The first type, located in the northeast of the SE subcluster, has larger velocity gradients, smaller masses, and nearly critical mass-per-unit-length ratios. The other type, located in the southwest of the SE subcluster, has the opposite properties. Several YSOs are formed along two filaments which have supercritical mass per unit length ratios, while filaments with nearly critical mass-per-unit-length ratios are not associated with YSOs, suggesting that stars are formed on gravitationally unstable filaments.
Akihito Endo - One of the best experts on this subject based on the ideXlab platform.
-
characterization and emended description of lactobacillus kunkeei as a fructophilic lactic acid bacterium
International Journal of Systematic and Evolutionary Microbiology, 2012Co-Authors: Akihito Endo, Sanae Okada, Tomohiro Irisawa, Yuka Futagawaendo, Katsumi Takano, Maret Du Toit, Leon M T DicksAbstract:Lactobacillus kunkeei is an inhabitant of fructose-rich niches and is a potential member of the fructophilic lactic acid bacteria. In the present study, the phylogenetic and biochemical characteristics of the type strain and eight isolates of L. kunkeei, originating from wine, flowers and honey, were studied. The nine isolates, including the type strain, formed a well-defined phylogenetic subcluster based on the analysis of 16S rRNA gene sequences. The subcluster was not closely related to other Subclusters in the Lactobacillus phylogenetic group. Biochemically, the eight new isolates showed typical fructophilic characteristics. The eight isolates grew poorly on glucose, but grew well on fructose. Good growth on glucose was only recorded in the presence of electron acceptors. The type strain of L. kunkeei differed from the other isolates only on the basis of poor growth on fructose. Although they belong to a group of obligately heterofermentative lactic acid bacteria, all nine isolates, including the type strain, produced almost equimolar amounts of lactic acid and acetic acid and very little ethanol from glucose. Eight of the isolates can thus be regarded as typical ‘obligately’ fructophilic lactic acid bacteria. Although the type strain of L. kunkeei was phenotypically slightly different from the other isolates, it possessed several important fructophilic characteristics. On the basis of the evidence gathered in this study, the type strain of L. kunkeei is recognized as a member of the ‘obligately’ fructophilic lactic acid bacteria.
-
reclassification of the genus leuconostoc and proposals of fructobacillus fructosus gen nov comb nov fructobacillus durionis comb nov fructobacillus ficulneus comb nov and fructobacillus pseudoficulneus comb nov
International Journal of Systematic and Evolutionary Microbiology, 2008Co-Authors: Akihito Endo, Sanae OkadaAbstract:A taxonomic study was made of the genus Leuconostoc. The species in the genus were divided into three Subclusters by phylogenetic analysis based on the 16S rRNA gene sequences. The three Subclusters were the Leuconostoc mesenteroides subcluster (comprising L. carnosum, L. citreum, L. gasicomitatum, L. gelidum, L. inhae, L. kimchii, L. lactis, L. mesenteroides and L. pseudomesenteroides), the L. fructosum subcluster (L. durionis, L. ficulneum, L. fructosum and L. pseudoficulneum) and the L. fallax subcluster (L. fallax). Phylogenetic trees based on the sequences of the 16S–23S rRNA gene intergenic spacer region, the rpoC gene or the recA gene indicated a good correlation with the phylogenetic tree based on 16S rRNA gene sequences. The species in the L. fructosum subcluster were morphologically distinguishable from the species in the L. mesenteroides subcluster and L. fallax as species in the L. fructosum subcluster had rod-shaped cells. In addition, the four species in the L. fructosum subcluster needed an electron acceptor for the dissimilation of d-glucose and produced acetic acid from d-glucose rather than ethanol. On the basis of evidence presented in this study, it is proposed that the four species in the L. fructosum subcluster, Leuconostoc durionis, Leuconostoc ficulneum, Leuconostoc fructosum and Leuconostoc pseudoficulneum, should be transferred to a novel genus, Fructobacillus gen. nov., as Fructobacillus durionis comb. nov. (type strain D-24T=LMG 22556T=CCUG 49949T), Fructobacillus ficulneus comb. nov. (type strain FS-1T=DSM 13613T=JCM 12225T), Fructobacillus fructosus comb. nov. (type strain IFO 3516T=DSM 20349T=JCM 1119T=NRIC 1058T) and Fructobacillus pseudoficulneus comb. nov. (type strain LC-51T=DSM 15468T=CECT 5759T). The type species of the genus Fructobacillus is Fructobacillus fructosus gen. nov., comb. nov.. No significant physiological and biochemical differences were found between the species in the L. mesenteroides subcluster and L. fallax in the present study and thus L. fallax remains as a member of the genus Leuconostoc.
P.k. Gupta - One of the best experts on this subject based on the ideXlab platform.
-
the use of microsatellites for detecting dna polymorphism genotype identification and genetic diversity in wheat
Theoretical and Applied Genetics, 2000Co-Authors: Manoj Prasad, Harindra S. Balyan, Rajeev K Varshney, P.k. GuptaAbstract:A set of 20 wheat microsatellite markers was used with 55 elite wheat genotypes to examine their utility (1) in detecting DNA polymorphism, (2)in the identifying genotypes and (3) in estimating genetic diversity among wheat genotypes. The 55 elite genotypes of wheat used in this study originated in 29 countries representing six continents. A total of 155 alleles were detected at 21 loci using the above microsatellite primer pairs (only 1 primer amplified 2 loci; all other primers amplified 1 locus each). Of the 20 primers amplifying 21 loci, 17 primers and their corresponding 18 loci were assigned to 13 different chromosomes (6 chromosomes of the A genome, 5 chromosomes of the B genome and 2 chromosomes of the D genome). The number of alleles per locus ranged from 1 to 13, with an average of 7.4 alleles per locus. The values of average polymorphic information content (PIC) and the marker index (MI) for these markers were estimated to be 0.71 and 0.70, respectively. The (GT)n microsatellites were found to be the most polymorphic. The genetic similarity (GS) coefficient for all possible 1485 pairs of genotypes ranged from 0.05 to 0.88 with an average of 0.23. The dendrogram, prepared on the basis of similarity matrix using the UPGMA algorithm, delineated the above genotypes into two major clusters (I and II), each with two Subclusters (Ia, Ib and IIa, IIb). One of these Subclusters (Ib) consisted of a solitary genotype (E3111) from Portugal, so that it was unique and diverse with respect to all other genotypes belonging to cluster I and placed in subcluster Ia. Using a set of only 12 primer pairs, we were able to distinguish a maximum of 48 of the above 55 wheat genotypes. The results demonstrate the utility of microsatellite markers for detecting polymorphism leading to genotype identification and for estimating genetic diversity.
-
the use of microsatellites for detecting dna polymorphism genotype identification and genetic diversity in wheat
Theoretical and Applied Genetics, 2000Co-Authors: Manoj Prasad, Harindra S. Balyan, Rajeev K Varshney, J K Roy, P.k. GuptaAbstract:A set of 20 wheat microsatellite markers was used with 55 elite wheat genotypes to examine their utility (1) in detecting DNA polymorphism, (2)in the identifying genotypes and (3) in estimating genetic diversity among wheat genotypes. The 55 elite genotypes of wheat used in this study originated in 29 countries representing six continents. A total of 155 alleles were detected at 21 loci using the above microsatellite primer pairs (only 1 primer amplified 2 loci; all other primers amplified 1 locus each). Of the 20 primers amplifying 21 loci, 17 primers and their corresponding 18 loci were assigned to 13 different chromosomes (6 chromosomes of the A genome, 5 chromosomes of the B genome and 2 chromosomes of the D genome). The number of alleles per locus ranged from 1 to 13, with an average of 7.4 alleles per locus. The values of average polymorphic information content (PIC) and the marker index (MI) for these markers were estimated to be 0.71 and 0.70, respectively. The (GT)n microsatellites were found to be the most polymorphic. The genetic similarity (GS) coefficient for all possible 1485 pairs of genotypes ranged from 0.05 to 0.88 with an average of 0.23. The dendrogram, prepared on the basis of similarity matrix using the UPGMA algorithm, delineated the above genotypes into two major clusters (I and II), each with two Subclusters (Ia, Ib and IIa, IIb). One of these Subclusters (Ib) consisted of a solitary genotype (E3111) from Portugal, so that it was unique and diverse with respect to all other genotypes belonging to cluster I and placed in subcluster Ia. Using a set of only 12 primer pairs, we were able to distinguish a maximum of 48 of the above 55 wheat genotypes. The results demonstrate the utility of microsatellite markers for detecting polymorphism leading to genotype identification and for estimating genetic diversity.
Erik Rosolowsky - One of the best experts on this subject based on the ideXlab platform.
-
carma large area star formation survey structure and kinematics of dense gas in serpens main
The Astrophysical Journal, 2014Co-Authors: Katherine I Lee, Manuel Fernandezlopez, Shaye Storm, Leslie W Looney, Lee G Mundy, Dominique Seguracox, Peter Teuben, Erik RosolowskyAbstract:We present observations of NL_2H^+ (J = 1 -> 0), HCO^+ (J = 1 -> 0), and HCN (J = 1 -> 0) toward the Serpens Main molecular cloud from the CARMA Large Area Star Formation Survey (CLASSy). We mapped 150 arcmin(2) of Serpens Main with an angular resolution of ~7". The gas emission is concentrated in two Subclusters (the NW and SE Subclusters). The SE subcluster has more prominent filamentary structures and more complicated kinematics compared to the NW subcluster. The majority of gas in the two Subclusters has subsonic to sonic velocity dispersions. We applied a dendrogram technique with N_2H^+(1-0) to study the gas structures; the SE subcluster has a higher degree of hierarchy than the NW subcluster. Combining the dendrogram and line fitting analyses reveals two distinct relations: a flat relation between nonthermal velocity dispersion and size, and a positive correlation between variation in velocity centroids and size. The two relations imply a characteristic depth of 0.15 pc for the cloud. Furthermore, we have identified six filaments in the SE subcluster. These filaments have lengths of ~0.2 pc and widths of ~0.03 pc, which is smaller than a characteristic width of 0.1 pc suggested by Herschel observations. The filaments can be classified into two types based on their properties. The first type, located in the northeast of the SE subcluster, has larger velocity gradients, smaller masses, and nearly critical mass-per-unit-length ratios. The other type, located in the southwest of the SE subcluster, has the opposite properties. Several YSOs are formed along two filaments which have supercritical mass per unit length ratios, while filaments with nearly critical massper- unit-length ratios are not associated with YSOs, suggesting that stars are formed on gravitationally unstable filaments.
-
carma large area star formation survey structure and kinematics of dense gas in serpens main
arXiv: Astrophysics of Galaxies, 2014Co-Authors: Katherine I Lee, Manuel Fernandezlopez, Shaye Storm, Leslie W Looney, Lee G Mundy, Dominique Seguracox, Peter Teuben, Erik RosolowskyAbstract:We present observations of N2H+(1-0), HCO+(1-0), and HCN(1-0) toward the Serpens Main molecular cloud from the CARMA Large Area Star Formation Survey (CLASSy). We mapped 150 square arcminutes of Serpens Main with an angular resolution of 7 arcsecs. The gas emission is concentrated in two Subclusters (the NW and SE Subclusters). The SE subcluster has more prominent filamentary structures and more complicated kinematics compared to the NW subcluster. The majority of gas in the two Subclusters has subsonic to sonic velocity dispersions. We applied a dendrogram technique with N2H+(1-0) to study the gas structures; the SE subcluster has a higher degree of hierarchy than the NW subcluster. Combining the dendrogram and line fitting analyses reveals two distinct relations: a flat relation between nonthermal velocity dispersion and size, and a positive correlation between variation in velocity centroids and size. The two relations imply a characteristic depth of 0.15 pc for the cloud. Furthermore, we have identified six filaments in the SE subcluster. These filaments have lengths of 0.2 pc and widths of 0.03 pc, which is smaller than a characteristic width of 0.1 pc suggested by Herschel observations. The filaments can be classified into two types based on their properties. The first type, located in the northeast of the SE subcluster, has larger velocity gradients, smaller masses, and nearly critical mass-per-unit-length ratios. The other type, located in the southwest of the SE subcluster, has the opposite properties. Several YSOs are formed along two filaments which have supercritical mass per unit length ratios, while filaments with nearly critical mass-per-unit-length ratios are not associated with YSOs, suggesting that stars are formed on gravitationally unstable filaments.
G P Garmire - One of the best experts on this subject based on the ideXlab platform.
-
age gradients in the stellar populations of massive star forming regions based on a new stellar chronometer
The Astrophysical Journal, 2014Co-Authors: Konstantin V Getman, Eric D Feigelson, Michael A Kuhn, Patrick S Broos, Leisa K Townsley, T Naylor, Matthew S Povich, K L Luhman, G P GarmireAbstract:A major impediment to understanding star formation in massive star-forming regions (MSFRs) is the absence of a reliable stellar chronometer to unravel their complex star formation histories. We present a new estimation of stellar ages using a new method that employs near-infrared (NIR) and X-ray photometry, Age JX . Stellar masses are derived from X-ray luminosities using the LX -M relation from the Taurus cloud. J-band luminosities are compared to mass-dependent pre-main-sequence (PMS) evolutionary models to estimate ages. Age JX is sensitive to a wide range of evolutionary stages, from disk-bearing stars embedded in a cloud to widely dispersed older PMS stars. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) project characterizes 20 OB-dominated MSFRs using X-ray, mid-infrared, and NIR catalogs. The Age JX method has been applied to 5525 out of 31,784 MYStIX Probable Complex Members. We provide a homogeneous set of median ages for over 100 Subclusters in 15 MSFRs; median subcluster ages range between 0.5 Myr and 5 Myr. The important science result is the discovery of age gradients across MYStIX regions. The wide MSFR age distribution appears as spatially segregated structures with different ages. The Age JX ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed populations. The NIR color index J – H, a surrogate measure of extinction, can serve as an approximate age predictor for young embedded clusters.
-
age gradients in the stellar populations of massive star forming regions based on a new stellar chronometer
arXiv: Solar and Stellar Astrophysics, 2014Co-Authors: Konstantin V Getman, Eric D Feigelson, Michael A Kuhn, Patrick S Broos, Leisa K Townsley, T Naylor, Matthew S Povich, K L Luhman, G P GarmireAbstract:A major impediment to understanding star formation in massive star forming regions (MSFRs) is the absence of a reliable stellar chronometer to unravel their complex star formation histories. We present a new estimation of stellar ages using a new method that employs near-infrared (NIR) and X-ray photometry, AgeJX. Stellar masses are derived from X-ray luminosities using the Lx - Mass relation from the Taurus cloud. J-band luminosities are compared to mass-dependent pre-main-sequence evolutionary models to estimate ages. AgeJX is sensitive to a wide range of evolutionary stages, from disk-bearing stars embedded in a cloud to widely dispersed older pre-main sequence stars. The MYStIX (Massive Young Star-Forming Complex Study in Infrared and X-ray) project characterizes 20 OB-dominated MSFRs using X-ray, mid-infrared, and NIR catalogs. The AgeJX method has been applied to 5525 out of 31,784 MYStIX Probable Complex Members. We provide a homogeneous set of median ages for over a hundred Subclusters in 15 MSFRs; median subcluster ages range between 0.5 Myr and 5 Myr. The important science result is the discovery of age gradients across MYStIX regions. The wide MSFR age distribution appears as spatially segregated structures with different ages. The AgeJX ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed populations. The NIR color index J-H, a surrogate measure of extinction, can serve as an approximate age predictor for young embedded clusters.
