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Reactivity, photolability, and computational studies of the ruthenium nitrosyl complex with a substituted cyclam fac-[Ru(NO)Cl(2)(kappa(3)N(4),N(8),N(11)(1-carboxypropyl)cyclam)]Cl center dot H(2)O

DORO, Fabio G.; PEPE, Iuri M.; GALEMBECK, Sergio E.; CARLOS, Rose M.; ROCHA, Zenis N. da; BERTOTTI, Mauro; TFOUNI, Elia
Fonte: ROYAL SOC CHEMISTRY Publicador: ROYAL SOC CHEMISTRY
Tipo: Artigo de Revista Científica
Português
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Chemical reactivity, photolability, and computational studies of the ruthenium nitrosyl complex with a substituted cyclam, fac-[Ru(NO)Cl(2)(kappa(3)N(4),N(8),N(11)(1-carboxypropyl)cyclam)]Cl center dot H(2)O ((1-carboxypropyl) cyclam = 3-(1,4,8,11-tetraazacyclotetradecan-1-yl) propionic acid)), (I) are described. Chloride ligands do not undergo aquation reactions (at 25 degrees C, pH 3). The rate of nitric oxide (NO) dissociation (k(obs-NO)) upon reduction of I is 2.8 s(-1) at 25 +/- 1 degrees C (in 0.5 mol L(-1) HCl), which is close to the highest value found for related complexes. The uncoordinated carboxyl of I has a pK(a) of similar to 3.3, which is close to that of the carboxyl of the non coordinated (1-carboxypropyl) cyclam (pK(a) = 3.4). Two additional pK(a) values were found for I at similar to 8.0 and similar to 11.5. Upon electrochemical reduction or under irradiation with light (lambda(irr) = 350 or 520 nm; pH 7.4), I releases NO in aqueous solution. The cyclam ring N bound to the carboxypropyl group is not coordinated, resulting in a fac configuration that affects the properties and chemical reactivities of I, especially as NO donor, compared with analogous trans complexes. Among the computational models tested, the B3LYP/ECP28MDF...

The effects of hydrogen sulfide on the polymer electrolyte membrane fuel cell anode catalyst: H(2)S-Pt/C interaction products

LOPES, Thiago; PAGANIN, Valdecir A.; GONZALEZ, Ernesto R.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
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66.593525%
The performance of a polymer electrolyte membrane fuel cell (PEMFC) operating on a simulated hydrocarbon reformate is described. The anode feed stream consisted of 80% H(2),similar to 20% N(2), and 8 ppm hydrogen sulfide (H(2)S). Cell performance losses are calculated by evaluating cell potential reduction due to H(2)S contamination through lifetime tests. It is found that potential, or power, loss under this condition is a result of platinum surface contamination with elemental sulfur. Electrochemical mass spectroscopy (EMS) and electrochemical techniques are employed, in order to show that elemental sulfur is adsorbed onto platinum, and that sulfur dioxide is one of the oxidation products. Moreover, it is demonstrated that a possible approach for mitigating H(2)S poisoning on the PEMFC anode catalyst is to inject low levels of air into the H(2)S-contaminated anode feeding stream. (C) 2011 Elsevier B.V. All rights reserved.; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES); Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Thiago Lopes`s PhD scholarship; Thiago Lopes`s PhD scholarship[142097/2005-5]; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)...

Spectroscopy properties and energy level location of Gd(2)O(2)S:Pr(3+),Ce(3+)

Cebim, Marco Aurelio; Da Silva, Alison Abreu; Davolos, Marian Rosaly; Kasap, S; DeCorby, R; Ruda, H; Hegmann, F; Kashyap, R
Fonte: Wiley-v C H Verlag Gmbh Publicador: Wiley-v C H Verlag Gmbh
Tipo: Conferência ou Objeto de Conferência Formato: S171-S174
Português
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In this work we propose the study of the spectroscopy properties and the energy level location of Ce(3+) and Pr(3+) in Gd(2)O(2)S, along with the effects of Ce(4+) (Ce(2)O(2)S(2)) incorporation in Gd(2)O(2)S and Gd(2)O(2)S: Pr(3+) in order to understand the formation and position of the associated defects energy levels in relation to the band structure of Gd(2)O(2)S and Pr(3+) energy levels. Ce-, Pr(3+)-doped and Pr(3+), Ce-doped Gd(2)O(2)S were prepared by the sulfidization of a basic gadolinium carbonate with S(8) using H(2)/N(2) (3.0/97.0%) and air during the firing of the precursor. Samples were analyzed by X-ray diffraction in order to guarantee the formation of the Gd(2)O(2)S single phase. Diffuse reflectance spectroscopy and luminescent measurements (emission/excitation) were used to locate Ce(3+), Pr(3+) and defects energy levels in relation to the band structure of Gd(2)O(2)S. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Measurement of intracellular Ca2+ in single aequorin-injected and suspensions of fura-2-loaded ROS 17/2.8 cells and normal human osteoblasts. Effect of parathyroid hormone.

Schöfl, C; Cuthbertson, K S; Gallagher, J A; Pennington, S R; Cobbold, P H; Brabant, G; Hesch, R D; von zur Mühlen, A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/02/1991 Português
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It is known that parathyroid hormone (PTH) activates the cyclic AMP (cAMP) signalling pathway in osteoblasts. In recent years it has been suggested that an elevation of the intracellular free Ca2+ concentration ([Ca2+]i) may also be involved in the regulation of osteoblast function by PTH. However, this remains controversial. Here we investigated the effect of PTH on the [Ca2+]i of ROS 17/2.8 cells and normal human osteoblasts. The [Ca2+]i was measured in single aequorin-injected cells and in suspensions of cells loaded with fura-2. Human PTH-(1-38)-peptide (1-300 nM) had no effect on the [Ca2+]i in single aequorin-injected ROS 17/2.8 cells (n = 17) measured at various times after injection (1-20 h), or in suspensions of fura-2-loaded ROS 17/2.8 cells (n = 9). Ionomycin (1 microM) increased the [Ca2+]i in fura-2-loaded and single aequorin-injected ROS 17/2.8 cells by 285 +/- 60 nM (n = 9) and 312 +/- 99 nM (n = 6) respectively, indicating that both methods detect changes in [Ca2+]i with equal sensitivity. In contrast, human PTH-(1-38) (10-100 nM) markedly stimulated cAMP accumulation in ROS 17/2.8 cells. In single aequorin-injected normal human osteoblasts there was no change in the [Ca2+]i in response to 100 nM human PTH-(1-38) or 100 nM bovine PTH-(1-84) (n = 18). In contrast...

Antigenic modulation of mammary tumour virus envelope antigen or GR thymic lymphoma cells in relation to expressions of H-2, TL cell-surface antigens and THY1.

Hilgers, J.; Sonnenberg, A.; Nusse, R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1980 Português
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The MLr antigen, a mammary tumour virus-induced antigen on the surface of GR thymic lymphoma cells (GRSL) can be modulated from the cell surface upon incubation with specific antiserum for 1-2 h at 37 degrees C, followed by washing the cells. In contrast, a number of other cell-surface antigens on these GRSL cells cannot be modulated under similar conditions. These antigens include histocompatibility antigens of the H-2 complex (H-2.8 of the K-end and H-2dx(D) of the H-2dx haplotype) and two thymic markers, TL1.2 and Thy1.2. Antigenic modulation of MLr as tested by trypan-blue exclusion and by chromium51 release does not lead to a measurable change in the expression of H-2K, H-2D, TL and Thy1.2 antigens. These results could be confirmed by absorption analysis. The latter analysis showed that the number of antigenic sites per cell are about the same for MLr and the two H-2 antigens, while TL antigens are scarcer and Thy1.2 antigens are more abundant. The procedure of antigenic modulation showed that the MLr antigen resides on MTVgp52, the major protein of the envelope. There was no evidence of internal proteins, such as MTVp27, on the surface of GRSL cells.

Molecular relationship between private and public H-2 antigens as determined by antigen redistribution method

Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/08/1975 Português
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Molecular relationship of public H-2 antigens 1, 5, 6, 8, 11, 13, 25, and 28 to private antigens controlled by K and D regions was studied using the technique of antibody-induced resistance to complement- mediated cytotoxicity. The results indicate physical association in the cell membrane between H-2 antigens 1 and 23 of H-2-a, 8 and 31 of H- 2-d, 11 and 17 of H-2-q, 13 and 30 of H-2-q, 25 and 23 of H-2-k, and 28 and 31 of H-2-g. These results are in agreement with genetic mapping placing the determinants of antigens H-2.8, 11 and 25 in the K region , the determinant of antigen H-2.13 in the D region, and the determinants of antigens H-2.1 and 28 in either the K or the D region. In contrast to genetic mapping placing the determinant for antigen H-2.6 in the D region, we found that in the H-2-b haplotype the antigen is associated with K region antigen H-2.33 and H-2.32, and interpreted this result as evidence for two homologous H-2.5 sites controlled by opposite ends of the H-2 complex. Although the data do not prove that public antigens are carried by the same molecules as private ones, they demonstrate a close physical association in the membrane between the two groups of loci, K and D, coding for the first 33 classical H-2 antigens (with the exception of antigen H-2.7)...

Association of Genetic Variation in (FTO) with Risk of Obesity and Type 2 Diabetes with Data from 96,551 East and South Asians

Kilpeläinen, T. O.; Sekine, A.; Yajnik, C. S.; Takeuchi, F.; Yamamoto, K.; Mani, K. R.; Been, L. F.; Imamura, M.; Nakashima, E.; Fujisawa, T.; Karasawa, S.; Joglekar, C. V.; Fall, C. H. D.; Sham, P. C.; Shu, X.; Deng, H.; Ikegami, H.; Krishnaveni, G. V.;
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Português
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Aims/hypothesis: (FTO) harbours the strongest known obesity-susceptibility locus in Europeans. While there is growing evidence for a role for (FTO) in obesity risk in Asians, its association with type 2 diabetes, independently of BMI, remains inconsistent. To test whether there is an association of the (FTO) locus with obesity and type 2 diabetes, we conducted a meta-analysis of 32 populations including 96,551 East and South Asians. Methods: All studies published on the association between (FTO)-rs9939609 (or proxy [r(^2) > 0.98]) and BMI, obesity or type 2 diabetes in East or South Asians were invited. Each study group analysed their data according to a standardised analysis plan. Association with type 2 diabetes was also adjusted for BMI. Random-effects meta-analyses were performed to pool all effect sizes. Results: The (FTO)-rs9939609 minor allele increased risk of obesity by 1.25-fold/allele (p = 9.0 × 10(^{−19})), overweight by 1.13-fold/allele (p = 1.0 × 10(^{−11})) and type 2 diabetes by 1.15-fold/allele (p = 5.5 × 10(^{−8})). The association with type 2 diabetes was attenuated after adjustment for BMI (OR 1.10-fold/allele, p = 6.6 × 10(^{−5})). The (FTO)-rs9939609 minor allele increased BMI by 0.26 kg/m2 per allele (p = 2.8 × 10(^{−17}))...

Construction of a 2.8-megabase yeast artificial chromosome contig and cloning of the human methylthioadenosine phosphorylase gene from the tumor suppressor region on 9p21.

Olopade, O I; Pomykala, H M; Hagos, F; Sveen, L W; Espinosa, R; Dreyling, M H; Gursky, S; Stadler, W M; Le Beau, M M; Bohlander, S K
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 03/07/1995 Português
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Many human malignant cells lack methylthioadenosine phosphorylase (MTAP) enzyme activity. The gene (MTAP) encoding this enzyme was previously mapped to the short arm of chromosome 9, band p21-22, a region that is frequently deleted in multiple tumor types. To clone candidate tumor suppressor genes from the deleted region on 9p21-22, we have constructed a long-range physical map of 2.8 megabases for 9p21 by using overlapping yeast artificial chromosome and cosmid clones. This map includes the type IIFN gene cluster, the recently identified candidate tumor suppressor genes CDKN2 (p16INK4A) and CDKN2B (p15INK4B), and several CpG islands. In addition, we have identified other transcription units within the yeast artificial chromosome contig. Sequence analysis of a 2.5-kb cDNA clone isolated from a CpG island that maps between the IFN genes and CDKN2 reveals a predicted open reading frame of 283 amino acids followed by 1302 nucleotides of 3' untranslated sequence. This gene is evolutionarily conserved and shows significant amino acid homologies to mouse and human purine nucleoside phosphorylases and to a hypothetical 25.8-kDa protein in the pet gene (coding for cytochrome bc1 complex) region of Rhodospirillum rubrum. The location, expression pattern...

c-myc and immunoglobulin kappa light chain constant genes are on the 8q+ chromosome of three Burkitt lymphoma lines with t(2;8) translocations.

Rappold, G A; Hameister, H; Cremer, T; Adolph, S; Henglein, B; Freese, U K; Lenoire, G M; Bornkamm, G W
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/12/1984 Português
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We have determined the localization of c-myc and the immunoglobulin kappa light chain genes on the 8q+/2p- chromosomes of the three Burkitt lymphoma lines BL21, LY66 and LY91 with t(2;8) translocation by in situ hybridization. BL21 is characterized by a complex translocation in which a piece of chromosome 9 appears to be located between the fragments of chromosome 8 and 2 on the 8q+ chromosome. Our data indicate that in all three cell lines the c-myc gene is located on the 8q+ chromosome proximal to the breakpoint in band 8q24. In all cell lines examined the cluster of kappa variable genes has remained on the 2p- chromosome. In LY91 cells the major part of the joining region remained on 2p-, while the joining region has moved to 8q+ in the cell lines BL21 and LY66. In all three cell lines the constant kappa light chain gene was found on the 8q+ chromosome. The fact that an essentially identical pattern was found in the cell line BL21, with the complex translocation, suggests that the insertion of the piece of chromosome 9 into the 8q+ chromosome might be a secondary event. Our present data fit into the concept that in all Burkitt lymphoma lines investigated so far, including cases with t(8;14) and the variant translocations t(2;8) and t(8;22)...

N segment insertion and region-directed somatic hypermutation in a kappa gene of a t(2;8) chromosomal translocation.

Klobeck, H G; Combriato, G; Zachau, H G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 25/06/1987 Português
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A detailed molecular analysis of both reciprocal recombination products of the variant t(2;8) chromosomal translocation of the Burkitt lymphoma derived cell line JI and their germline counterparts was carried out. The breakpoint on chromosome 8 is localized 28 kb to the 3' side of the c-myc protooncogene, the breakpoint on chromosome 2 was found to be within an aberrantly rearranged VK gene (abbreviations ref. 1). Novel features of the immunoglobulin moiety involved in this process include insertion of extra nucleotides in the V-J junction which have the characteristics of a N segment as it has been found up to now only in heavy chain and T cell receptor genes; the occurrence of somatic mutations in 8q+ and not in 2p-. These data allow a reconstruction of the course of events in the cell line JI; remarkable sequence regularities at the chromosomal breakpoints consisting of symmetrically placed dinucleotides and elements related to the hepta- and nonanucleotide recombinase recognition sequences are discussed in the context of the translocation mechanism.

Excitation of H_2 and HD in shocks and PDRs

Bertoldi, F.; Draine, B. T.; Rosenthal, D.; Timmermann, R.; Howat, S. K. Ramsay; Geballe, T.; Feuchtgruber, H.; Drapatz, S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 24/09/2000 Português
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Photodissociation regions (PDRs) and shocks give rise to conspicuous emission from rotationally and vibrationally excited molecular hydrogen. This line emission has now been studied with ISO and from the ground in great detail. A remarkable discovery has been that toward the Orion outflow and other shock-excited regions, the H_2 level populations show a very high excitation component. We suggest that these high-excitation populations may arise from non-thermal pumping processes, such as H_2 formation and high-velocity ion-molecule collision in partially dissociative shocks. In PDRs such as NGC 7023 however, formation pumping is always less important than fluorescent pumping. We furthermore present two HD emission line detections toward Orion Peak 1. This enables the first comparison of the H_2 and the HD excitation, which surprisingly turn out to be identical.; Comment: 11 pages, 8 figures, uses newpasp.sty

A Characteristic Transmission Spectrum dominated by H$_{2}$O applies to the majority of HST/WFC3 exoplanet observations

Iyer, Aishwarya R.; Swain, Mark R.; Zellem, Robert T.; Line, Michael R.; Roudier, Gael; Rocha, Graca; Livingston, John H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/12/2015 Português
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Currently, 19 transiting exoplanets have published transmission spectra obtained with the Hubble/WFC3 G141 near-IR grism. Using this sample, we have undertaken a uniform analysis incorporating measurement-error debiasing of the spectral modulation due to H$_{2}$O, measured in terms of the estimated atmospheric scale height, ${H_s}$. For those planets with a reported H$_{2}$O detection (10 out of 19), the spectral modulation due to H$_{2}$O ranges from 0.9 to 2.9 ${H_s}$ with a mean value of 1.8 ${H_s}$. This spectral modulation is significantly less than predicted for clear atmospheres. For the group of planets in which H$_{2}$O has been detected, we find the individual spectra can be coherently averaged to produce a characteristic spectrum in which the shape, together with the spectral modulation of the sample, are consistent with a range of H$_{2}$O mixing ratios and cloud-top pressures, with a minimum H$_{2}$O mixing ratio of 23 ppm corresponding to the cloud-free case. Using this lower limit, we show that clouds or aerosols must block at least half of the atmospheric column that would otherwise be sampled by transmission spectroscopy in the case of a cloud-free atmosphere. We conclude that terminator-region clouds, with sufficient opacity to be opaque in slant-viewing geometry...

Detection of OH$^+$ and H$_2$O$^+$ towards Orion~KL

Gupta, H.; Rimmer, P.; Pearson, J. C.; Yu, S.; Herbst, E.; Harada, N.; Bergin, E. A.; Neufeld, D. A.; Melnick, G. J.; Bachiller, R.; Baechtold, W.; Bell, T. A.; Blake, G. A.; Caux, E.; Ceccarelli, C.; Cernicharo, J.; Chattopadhyay, G.; Comito, C.; Cabrit,
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 08/09/2010 Português
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We report observations of the reactive molecular ions OH$^+$, H$_2$O$^+$, and H$_3$O$^+$ towards Orion KL with Herschel/HIFI. All three $N=1-0$ fine-structure transitions of OH$^+$ at 909, 971, and 1033GHz and both fine-structure components of the doublet {\it ortho}-H$_2$O$^+$ $1_{11}-0_{00}$ transition at 1115 and 1139GHz were detected; an upper limit was obtained for H$_3$O$^+$. OH$^+$ and H$_2$O$^+$ are observed purely in absorption, showing a narrow component at the source velocity of 9 kms$^{-1}$, and a broad blueshifted absorption similar to that reported recently for HF and {\it para}-H$_{2}^{18}$O, and attributed to the low velocity outflow of Orion KL. We estimate column densities of OH$^+$ and H$_2$O$^+$ for the 9 km s$^{-1}$ component of $9 \pm 3 \times 10^{12}$cm$^{-2}$ and $7 \pm 2 \times 10^{12}$cm$^{-2}$, and those in the outflow of $1.9 \pm 0.7 \times 10^{13}$cm$^{-2}$ and $1.0 \pm 0.3 \times 10^{13}$cm$^{-2}$. Upper limits of $2.4\times 10^{12}$cm$^{-2}$ and $8.7\times 10^{12}$cm$^{-2}$ were derived for the column densities of {\it ortho} and {\it para}-H$_3$O$^+$ from transitions near 985 and 1657GHz. The column densities of the three ions are up to an order of magnitude lower than those obtained from recent observations of W31C and W49N. The comparatively low column densities may be explained by a higher gas density despite the assumption of a very high ionization rate.; Comment: 5 pages...

Quasi-two-dimensional $S=1/2$ magnetism of Cu[C$_6$H$_2$(COO)$_4$][C$_2$H$_5$NH$_3$]$_2$

Nath, R.; Padmanabhan, M.; Baby, S.; Thirumurugan, A.; Ehlers, D.; Hemmida, M.; von Nidda, H. -A. Krug; Tsirlin, A. A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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We report structural and magnetic properties of the spin-$\frac12$ quantum antiferromagnet Cu[C$_6$H$_2$(COO)$_4$][C$_2$H$_5$NH$_3$]$_2$ by means of single-crystal x-ray diffraction, magnetization, heat capacity, and electron spin resonance (ESR) measurements on polycrystalline samples, as well as band-structure calculations. The triclinic crystal structure of this compound features CuO$_4$ plaquette units connected into a two-dimensional framework through anions of the pyromellitic acid [C$_6$H$_2$(COO)$_4$]$^{4-}$. The ethylamine cations [C$_2$H$_5$NH$_3]^+$ are located between the layers and act as spacers. Magnetic susceptibility and heat capacity measurements establish a quasi-two-dimensional, weakly anisotropic and non-frustrated spin-$\frac12$ square lattice with the ratio of the couplings $J_a/J_c\simeq 0.7$ along the $a$ and $c$ directions, respectively. No clear signatures of the long-range magnetic order are seen in thermodynamic measurements down to 1.8\,K. However, the gradual broadening of the ESR line suggests that magnetic ordering occurs at lower temperatures. Leading magnetic couplings are mediated by the organic anion of the pyromellitic acid and exhibit a non-trivial dependence on the Cu--Cu distance, with the stronger coupling between those Cu atoms that are further apart.; Comment: 10 pages...

Magnetic fields around evolved stars: further observations of H$_2$O maser polarization

Leal-Ferreira, M. L.; Vlemmings, W. H. T.; Kemball, A.; Amiri, N.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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We aim to detect the magnetic field and infer its properties around four AGB stars using H$_2$O maser observations. The sample we observed consists of the following sources: the semi-regular variable RT Vir and the Mira variables AP Lyn, IK Tau, and IRC+60370. We observed the 6$_{1,6}-5_{2,3}$ H$_2$O maser rotational transition, in full-polarization mode, to determine its linear and circular polarization. Based on the Zeeman effect, one can infer the properties of the magnetic field from the maser polarization analysis. We detected a total of 238 maser features, in three of the four observed sources. No masers were found toward AP Lyn. The observed masers are all located between 2.4 and 53.0 AU from the stars. Linear and circular polarization was found in 18 and 11 maser features, respectively. We more than doubled the number of AGB stars in which magnetic field has been detected from H$_2$O maser polarization, as our results confirm the presence of fields around IK Tau, RT Vir and IRC+60370. The strength of the field along the line of sight is found to be between 47 and 331 mG in the H$_2$O maser region. Extrapolating this result to the surface of the stars, assuming a toroidal field ($\propto$ r$^{-1}$), we find magnetic fields of 0.3-6.9 G on the stellar surfaces. If...

Will This Paper Increase Your h-index? Scientific Impact Prediction

Dong, Yuxiao; Johnson, Reid A.; Chawla, Nitesh V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/12/2014 Português
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56.6356%
Scientific impact plays a central role in the evaluation of the output of scholars, departments, and institutions. A widely used measure of scientific impact is citations, with a growing body of literature focused on predicting the number of citations obtained by any given publication. The effectiveness of such predictions, however, is fundamentally limited by the power-law distribution of citations, whereby publications with few citations are extremely common and publications with many citations are relatively rare. Given this limitation, in this work we instead address a related question asked by many academic researchers in the course of writing a paper, namely: "Will this paper increase my h-index?" Using a real academic dataset with over 1.7 million authors, 2 million papers, and 8 million citation relationships from the premier online academic service ArnetMiner, we formalize a novel scientific impact prediction problem to examine several factors that can drive a paper to increase the primary author's h-index. We find that the researcher's authority on the publication topic and the venue in which the paper is published are crucial factors to the increase of the primary author's h-index, while the topic popularity and the co-authors' h-indices are of surprisingly little relevance. By leveraging relevant factors...

Molecular gas and dust in the highly magnified z = 2.8 galaxy behind the Bullet Cluster

Johansson, Daniel; Horellou, Cathy; Lopez-Cruz, Omar; Muller, Sebastien; Birkinshaw, Mark; Black, John H.; Bremer, Malcolm N.; Wall, William F.; Bertoldi, Frank; Castillo, Edgar; Ibarra-Medel, Hector Javier
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/08/2012 Português
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56.62181%
The gravitational magnification provided by massive galaxy clusters makes it possible to probe the physical conditions in distant galaxies that are of lower luminosity than those in blank fields and likely more representative of the bulk of the high-redshift galaxy population. We aim to constrain the basic properties of molecular gas in a strongly magnified submm galaxy located behind the massive Bullet Cluster. This galaxy (SMM J0658) is split into three images, with a total magnification factor of almost 100. We used the Australia Telescope Compact Array (ATCA) to search for {12}CO(1--0) and {12}CO(3--2) line emission from SMM J0658. We also used the SABOCA bolometer camera on the Atacama Pathfinder EXperiment (APEX) telescope to measure the continuum emission at 350 micron. CO(1--0) and CO(3--2) are detected at 6.8 sigma and 7.5 sigma significance when the spectra toward the two brightest images of the galaxy are combined. From the CO(1-0) luminosity we derive a mass of cold molecular gas of (1.8 \pm 0.3) * 10^9 Msun, using the CO to H_2 conversion factor commonly used for luminous infrared galaxies. This is 45 \pm 25 % of the stellar mass. From the width of the CO lines we derive a dynamical mass within the CO-emitting region L of (1.3 \pm 0.4) * 10^10 (L/1 kpc) Msun. We refine the redshift determination of SMM J0658 to z=2.7793 \pm 0.0003. Continuum emission at 350 micron from SMM J0658 was detected with SABOCA at a signal-to-noise ratio of 3.6. We study the spectral energy distribution of SMM J0658 and derive a dust temperature of 33\pm 5 K and a dust mass of 1.1*10^7 Msun. SMM J0658 is one of the least massive submm galaxies discovered so far. As a likely representative of the bulk of the submm galaxy population...

Energetics of the molecular gas in the H_2 luminous radio galaxy 3C 326: Evidence for negative AGN feedback

Nesvadba, N. P. H.; Boulanger, F.; Salome, P.; Guillard, P.; Lehnert, M. D.; Ogle, P.; Appleton, P.; Falgarone, E.; Forets, G. Pineau des
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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We present a detailed analysis of the gas conditions in the H_2 luminous radio galaxy 3C326N at z~0.1, which has a low star formation rate (SFR~0.07 M_sun/yr) in spite of a gas surface density similar to those in starburst galaxies. Its star-formation efficiency is likely a factor ~20-30 lower than those of ordinary star-forming galaxies. Combining new IRAM CO emission-line interferometry with existing Spitzer mid-infrared spectroscopy, we find that the luminosity ratio of CO and pure rotational H_2 line emission is factors 10-100 lower than what is usually found. This may suggest that most of the molecular gas is warm. The Na D absorption-line profile of 3C326N in the optical suggests an outflow with a terminal velocity of ~ -1800 km/s and a mass outflow rate of 30-40 M_sun/yr, which cannot be explained by star formation. The mechanical power implied by the wind, of order 10^43 erg/s, is comparable to the bolometric luminosity of the emission lines of ionized and molecular gas. To explain these observations, we propose a scenario where a small fraction of the mechanical energy of the radio jet is deposited in the the interstellar medium of 3C326N, which powers the outflow, and the line emission through a mass momentum and energy exchange between the different phases in the ISM. Dissipation times are of order 10^7-8 yrs...

Enhanced Warm H_2 Emission in the Compact Group Mid-infrared "Green Valley"

Cluver, M. E.; Appleton, P. N.; Ogle, P.; Jarrett, T. H.; Rasmussen, J.; Lisenfeld, U.; Guillard, P.; Verdes-Montenegro, L.; Antonucci, R.; Bitsakis, T.; Charmandaris, V.; Boulanger, F.; Egami, E.; Xu, C. K.; Yun, M. S.
Fonte: American Astronomical Society Publicador: American Astronomical Society
Tipo: Article; PeerReviewed Formato: application/pdf; application/pdf
Publicado em 10/03/2013 Português
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We present results from a Spitzer mid-infrared spectroscopy study of a sample of 74 galaxies located in 23 Hickson Compact Groups (HCGs), chosen to be at a dynamically active stage of H I depletion. We find evidence for enhanced warm H_2 emission (i.e., above that associated with UV excitation in star-forming regions) in 14 galaxies (~20%), with 8 galaxies having extreme values of L(H_2 S(0)-S(3))/L(7.7 μm polycyclic aromatic hydrocarbon), in excess of 0.07. Such emission has been seen previously in the compact group HCG 92 (Stephan's Quintet), and was shown to be associated with the dissipation of mechanical energy associated with a large-scale shock caused when one group member collided, at high velocity, with tidal debris in the intragroup medium. Similarly, shock excitation or turbulent heating is likely responsible for the enhanced H_2 emission in the compact group galaxies, since other sources of heating (UV or X-ray excitation from star formation or active galactic nuclei) are insufficient to account for the observed emission. The group galaxies fall predominantly in a region of mid-infrared color-color space identified by previous studies as being connected to rapid transformations in HCG galaxy evolution. Furthermore, the majority of H_2-enhanced galaxies lie in the optical "green valley" between the blue cloud and red sequence...

Detection of Powerful Mid-IR H_2 Emission in the Bridge between the Taffy Galaxies

Peterson, B. W.; Appleton, P. N.; Helou, G.; Guillard, P.; Jarrett, T. H.; Cluver, M. E.; Ogle, P.; Struck, C.; Boulanger, F.
Fonte: American Astronomical Society Publicador: American Astronomical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 20/05/2012 Português
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We report the detection of strong, resolved emission from warm H_2 in the Taffy galaxies and bridge. Relative to the continuum and faint polyclic aromatic hydrocarbon (PAH) emission, the H_2 emission is the strongest in the connecting bridge, approaching L(H_2)/L(PAH 8 μm) = 0.1 between the two galaxies, where the purely rotational lines of H_2 dominate the mid-infrared spectrum in a way very reminiscent of the group-wide shock in the interacting group Stephan's Quintet (SQ). The surface brightness in the 0-0 S(0) and S(1) H_2 lines in the bridge is more than twice that observed at the center of the SQ shock. We observe a warm H2 mass of 4.2 × 10^8 M_☉ in the bridge, but taking into account the unobserved bridge area, the total warm mass is likely to be twice this value. We use excitation diagrams to characterize the warm molecular gas, finding an average surface mass of ~5 × 10^6 M_☉ kpc^(–2) and typical excitation temperatures of 150-175 K. H_2 emission is also seen in the galaxy disks, although there the emission is more consistent with normal star-forming galaxies. We investigate several possible heating mechanisms for the bridge gas but favor the conversion of kinetic energy from the head-on collision via turbulence and shocks as the main heating source. Since the cooling time for the warm H_2 is short (~5000 yr)...