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New insights on surface-enhanced Raman scattering based on controlled aggregation and spectroscopic studies, DFT calculations and symmetry analysis for 3,6-bi-2-pyridyl-1,2,4,5-tetrazine adsorbed onto citrate-stabilized gold nanoparticles

MELO, Vitor H. S. de; ZAMARION, Vitor M.; ARAKI, Koiti; TOMA, Henrique E.
Fonte: WILEY-BLACKWELL Publicador: WILEY-BLACKWELL
Tipo: Artigo de Revista Científica
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Asystematic study on the surface-enhanced Raman scattering (SERS) for 3,6-bi-2-pyridyl-1,2,4,5-tetrazine (bptz) adsorbed onto citrate-modified gold nanoparticles (cit-AuNps) was carried out based on electronic and vibrational spectroscopy and density functional methods. The citrate/bptz exchange was carefully controlled by the stepwise addition of bptz to the cit-AuNps, inducing flocculation and leading to the rise of a characteristic plasmon coupling band in the visible region. Such stepwise procedure led to a uniform decrease of the citrate SERS signals and to the rise of characteristic peaks of bptz, consistent with surface binding via the N heterocyclic atoms. In contrast, single addition of a large amount of bptz promoted complete aggregation of the nanoparticles, leading to a strong enhancement of the SERS signals. In this case, from the distinct Raman profiles involved, the formation of a new SERS environment became apparent, conjugating the influence of the local hot spots and charge-transfer (CT) effects. The most strongly enhanced vibrations belong to a(1) and b(2) representations, and were interpreted in terms of the electromagnetic and the CT mechanisms: the latter involving significant contribution of vibronic coupling in the system. Copyright (C) 2010 John Wiley & Sons...

Stress hormones increase cell proliferation and regulates interleukin-6 secretion in human oral squamous cell carcinoma cells

Bernabe, Daniel G.; Tamae, Adriano C.; Biasoli, Eder Ricardo; Oliveira, Sandra H. P.
Fonte: Academic Press Inc. Elsevier B.V. Publicador: Academic Press Inc. Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 574-583
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 06/59835-0; Patients with oral cancer can have high psychological distress levels, but the effects of stress-related hormones on oral cancer cells and possible mechanisms underlying these relationships are unknown. In this study, we have investigated the effects of stress-related hormones on interleukin-6 (IL-6) secretion and proliferation of oral squamous cell carcinoma (OSCC) cells. The effects of norepinephrine (NE), and cortisol were studied in SCC9. SCC15, and SCC25 cells and effects of isoproterenol in SCC9 and SCC25 cells. Real-time PCR studies revealed constitutive beta 1- and beta 2-adrenergic receptors (beta-ARs) expression in the SCC9. SCC15, and SCC25 cells. The results showed that NE and isoproterenol significantly enhanced IL-6 mRNA expression and protein production in supernatants of SCC9 and SCC25 cells. Physiological stress levels of NE and isoproterenol (10 mu M) at 1 h elicited the most robust IL-6 increase. Regarding IL-6 secretion, 10 mu M NE induced a 5-fold increase at 1 h, 3.7-fold increase at 6 h, and 3.2-fold at 24 h in SCC9 cells. These effects were blocked by the beta-adrenergic antagonist propranolol, supporting a role for beta-ARs in IL-6 secretion. The effects of cortisol varied according to the hormone concentration. Pharmacological concentrations of cortisol (1000 nM) inhibited IL-6 production by SCC9 and SCC25 cells. Cortisol dose that simulates stress conditions (10 nM) tended to increase IL-6 expression in SCC9 cells. Hormonal doses that simulate stress conditions (10 mu M NE...

Studies of the biosynthesis of 3,6-dideoxyhexoses: molecular cloning and characterization of the asc (ascarylose) region from Yersinia pseudotuberculosis serogroup VA.

Thorson, J S; Lo, S F; Ploux, O; He, X; Liu, H W
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1994 Português
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The 3,6-dideoxyhexoses are found in the lipopolysaccharides of gram-negative bacteria, where they have been shown to be the dominant antigenic determinants. Of the five 3,6-dideoxyhexoses known to occur naturally, four have been found in various strains of Salmonella enterica (abequose, tyvelose, paratose, and colitose) and all five, including ascarylose, are present among the serotypes of Yersinia pseudotuberculosis. Although there exists one report of the cloning of the rfb region harboring the abequose biosynthetic genes from Y. pseudotuberculosis serogroup HA, the detailed genetic principles underlying a 3,6-dideoxyhexose polymorphism in Y. pseudotuberculosis have not been addressed. To extend the available information on the genes responsible for 3,6-dideoxyhexose formation in Yersinia spp. and facilitate a comparison with the established rfb (O antigen) cluster of Salmonella spp., we report the production of three overlapping clones containing the entire gene cluster required for CDP-ascarylose biosynthesis. On the basis of a detailed sequence analysis, the implications regarding 3,6-dideoxyhexose polymorphism among Salmonella and Yersinia spp. are discussed. In addition, the functional cloning of this region has allowed the expression of Ep (alpha-D-glucose cytidylyltransferase)...

Elaboration of a 3.6-kilodalton lipooligosaccharide, antibody against which is absent from human sera, is associated with serum resistance of Neisseria gonorrhoeae.

Schneider, H; Griffiss, J M; Mandrell, R E; Jarvis, G A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1985 Português
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Neisseria gonorrhoeae strains that resist lysis by normal human sera (NHS) do so, in part, because NHS contain immunoglobulin M (IgM) specific for lipooligosaccharide (LOS) antigens of serum-sensitive strains, but lack antibodies for LOS antigens that can serve as loci for immune lysis of serum-resistant (serr) strains. We used a monoclonal antibody (McAb), specific for an epitope within a 3.6-kilodalton (kDa) component of Neisseria meningitidis L8 LOS, that binds a 3.6-kDa gonococcal LOS component so that we could explore further serr gonococcal strains. The McAb bound to the LOS of 6 of 7 serr of strains but not to the LOS of 0 of 14 serum-sensitive and serum-intermediate gonococcal strains of diverse origin. We studied three serr strains further. Strain 7134 does not elaborate the 3.6-kDa LOS component and does not bind the McAb; strains WR220 and WR302 do elaborate the 3.6-kDa LOS component. The titer (log2) at which the McAb, diluted in NHS, lysed strain WR220 was 7.7; for WR302 it was 3.7, and for 7134 it was 0. Addition of McAb to NHS caused increased classical and alternative-pathway C3 deposition onto strain WR220, but only classical-pathway-activated C3 deposition onto strain WR302. The difference in lytic effectiveness of the McAb for the two strains...

Effects of hCG on progesterone concentrations and fertility in cyclic, lactating Alpine goats.

FONSECA, J. F. da; MAFFILI, V. V.; RODRIGUES, M. T.; SANTOS, A. D. F.; ROVAY, H.; PINTO NETO, A.; BRANDÃO, F. Z.; TORES, C. A. A.
Fonte: Animal Reproduction, v. 3, n. 4, p. 410-414, Oct./Dec. 2006. Publicador: Animal Reproduction, v. 3, n. 4, p. 410-414, Oct./Dec. 2006.
Tipo: Artigo em periódico indexado (ALICE)
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The objective of this study was to evaluate the effect of hCG administration on plasma progesterone concentrations in lactating Alpine goats during the natural breeding season. After detection of estrus, 124 does were randomly assigned to one of two treatments (T1 and T2). In T1 (n = 60) and T2 (n = 64), the animals received 1 ml of saline solution or 250 IU of hCG i.m., respectively, 5 days after the first detection of estrus and breeding. Plasma progesterone concentration (ng/mL) was determined from blood sampled (T1 = 12 and T2 = 13) on Days 0 (day of estrus), 5, 7, 13, 17, 21, 28 and 45 after breeding. Two control goats with short cycles and two nymphomaniac goats (one per treatment) were detected. Plasma progesterone concentration (mean ± SEM) for T1 and T2 females differed on Days 13, 17 (P < 0.005) and 21 (P < 0.075), being respectively 3.8 ± 0.2 and 6.6 ± 0.7 at Day 13; 3.6 ± 0.1 and 6.5 ± 0.7 at Day 17; 4.3 ± 0.4 and 6.4 ± 0.9 at Day 21. Pregnancy rates on Days 35 and 70 did not differ (P > 0.05) between T1 (78.3%) and T2 (84.4%) does. The hCG administration 5 days after breeding increased plasma progesterone concentrations on Days 13 to 21 but did not increase pregnancy rate.; 2006

The solution structure of uperin 3.6, an antibiotic peptide from the granular dorsal glands of the Australian toadlet, Uperoleia mjobergii

Chia, B.; Carver, J.; Mulhern, T.; Bowie, J.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Artigo de Revista Científica
Publicado em //1999 Português
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Uperin 3.6 (GVIDA5AKKVV10NVLKN15LF-NH2) is a wide-spectrum antibiotic peptide isolated from the Australian toadlet, Uperoleia mjobergii. With only 17 amino acid residues, it is smaller than most other wide-spectrum antibiotic peptides isolated from amphibians. In 50% (by vol.) trifluoroethanol, an NMR study and structure calculations indicate that uperin 3.6 adopts a well-defined amphipathic α-helix with distinct hydrophilic and hydrophobic faces. Examination of the activities of synthetic modifications of uperin 3.6 reveal that the three lysine residues are essential for antibiotic activity.; B.C.S. Chia, J.H. Bowie, J.A. Carver and T.D. Mulhern

Effet des changements du ratio alimentaire oméga-3/oméga-6 dans un modèle d’infarctus du myocarde reperfusé chez le rat

Rondeau, Isabelle
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
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Une mort cellulaire par apoptose impliquant un processus inflammatoire est observée dans le système limbique, suite à un infarctus du myocarde. Les oméga-3 et ses métabolites, en plus de leurs propriétés bénéfiques pour le système cardiovasculaire, réduisent l’inflammation, contrairement aux oméga-6 qui sont plus pro-inflammatoires. Comme le métabolisme de ces deux acides gras essentiels impliquent les mêmes enzymes, le ratio alimentaire oméga-3/6 aurait donc des impacts importants sur l'état inflammatoire et ainsi indirectement sur l'apoptose. Conséquemment, cette étude a pour but d'évaluer l'effet de différents ratios oméga-3/6 sur la taille de l’infarctus, l’inflammation et l’apoptose dans le système limbique suite à un infarctus du myocarde. Des rats Sprague-Dawley ont été aléatoirement distribués dans trois groupes contenant des ratios 1:1, 1:5 et 5:1 oméga-3/6. Ils ont été nourris pendant 2 semaines, suivie d’une occlusion de l’artère coronaire gauche descendante pendant 40 minutes et d’une période de reperfusion (15 min et 24 h). De hauts ratios d’oméga-3 (5:1 et 1:1) diminuent significativement la taille de l’infarctus de 32 % et augmentent l’activité d’Akt, impliquée dans la voie cardioprotectrice RISK...

3,6′-Dithiothalidomide, a new TNF-α synthesis inhibitor, attenuates the effect of Aβ1-42 intracerebroventricular injection on hippocampal neurogenesis and memory deficit

Russo, Isabella; Caracciolo, Luca; Tweedie, David; Choi, Sang-Ho; Greig, Nigel H.; Barlati, Sergio; Bosetti, Francesca
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Evidence indicates altered neurogenesis in neurodegenerative diseases associated with inflammation, including Alzheimer’s disease (AD). Neuroinflammation and its propagation have a critical role in the degeneration of hippocampal neurons, cognitive impairment and altered neurogenesis. Particularly, tumor necrosis factor (TNF)-α plays a central role in initiating and regulating the cytokine cascade during an inflammatory response and is up-regulated in brain of AD patients. In this study, we investigated the effects of a novel thalidomide-based TNF-α lowering drug, 3,6′-dithiothalidomide, on hippocampal progenitor cell proliferation, neurogenesis and memory tasks after intracerebroventricular (i.c.v.) injection of β-amyloid (Aß)1-42 peptide. Seven days after Aβ1-42 injection, a significant proliferation of hippocampal progenitor cells and memory impairment were evident. Four weeks after Aβ1–42 peptide injection, elevated numbers of surviving BrdU cells and newly formed neurons were detected. Treatment with 3,6′-dithiothalidomide attenuated these Aβ1-42 provoked effects. Our data indicate that although treatment with 3,6′-dithiothalidomide in part attenuated the increase in hippocampal neurogenesis caused by Aβ1-42-induced neuroinflammation...

Chemical Constituents from Bombacopsis glabra (Pasq.) A. Robyns: Complete ¹H and 13C NMR Assignments and X Ray Structure of 5-Hydroxy-3,6,7,8,4'-pentamethoxyflavone

Paula,Vanderlúcia F.; Barbosa,Luiz C. A .; Errington,William; Howarth,Oliver W.; Cruz,Mariluze P.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2002 Português
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The flavone 5-hydroxy-3,6,7,8,4'-pentamethoxyflavone (1) and the triterpenes lupenone, 9,19-cyclolanost-23-ene-3beta,25-diol (2), (24R)-9,19-cyclolanost-25-ene-3beta,24-diol (3) and (24S)-9,19-cyclolanost-25-ene-3beta,24-diol (4) were isolated from the hexane extract of the stem bark of Bombacopsis glabra (Bombacaceae). The structures were determined by 13C and ¹H NMR (1D and 2D) and mass spectrometry, and by comparison with literature data for triterpenes. The structure of the flavone 1 was unambiguously confirmed by a X-ray diffraction study. The five substances were isolated for the first time from Bombacaceae species.

An H2Co 6 cm maser pinpointing a possible circumstellar torus in IRAS 18566+0408

Linz, H.; Garay, G.; Olmi, L.; Goss, W. M.; Churchwell, E.; Hofner, P.; Rodríguez, L. F.; Kurtz, S.; Sewixo, M.; Araya, E.
Fonte: UNIV CHICAGO PRESS Publicador: UNIV CHICAGO PRESS
Tipo: Artículo de revista
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Artículo de publicación ISI; We report observations of 6 cm, 3.6 cm, 1.3 cm, and 7 mm radio continuum, conducted with the Very Large Array, toward IRAS 18566+0408, one of the few sources known to harbor H(2)CO6 cm maser emission. Our observations reveal that the emission is dominated by an ionized jet at centimeter wavelengths. Spitzer IRAC images from GLIMPSE support this interpretation, given the presence of 4.5 mu m excess emission at approximately the same orientation as the centimeter continuum. The 7 mm emission is dominated by thermal dust from a flattened structure almost perpendicular to the ionized jet; thus, the 7 mm emission appears to trace a torus associated with a young massive stellar object. The H2CO 6 cm maser is coincident with the center of the torus-like structure. Our observations rule out radiative pumping via radio continuum as the excitation mechanism for the H2CO 6 cm maser in IRAS 18566+0408.

Conformational dynamics of substituted N-acetyl-N-phenylbenzylamines. H-1-DNMR and AM1-MO study

Jullian, Carolina; Araya Maturana, Ramiro Juan; Pessoa, H.; Valderrama, J.; Saitz B., C.; Weiss López, Boris Enrique
Fonte: SOCIEDAD CHILENA DE QUIMICA Publicador: SOCIEDAD CHILENA DE QUIMICA
Tipo: Artículo de revista
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Activation parameters for the rotation around the methylene-nitrogen single bond found in a series of four 2,2'-disubstituted N-acetyl-N-phenylbenzylamines, dissolved in DMSO-d(6), were measured employing the temperature dependence of the H-1-NMR spectrum lineshape between 340 and 400 K. The results are (I) 2 - [N-acetyl -N- (2-acetamidophenyl) aminomethyl] phenyl acetate DeltaG(not equal) =79.9 +/-2.0 kJ/mol (370K), DeltaH(not equal) =96.2 +/-6.0 kJ/mol and DeltaS(not equal) =+45 +/- 20 J/Kmol; (II) 2 [N - acetyl - N - (2-acetyioxybenzyl)amino]benzylacetate DeltaG(not equal) =82.0 +/-2.0 kJ/mol (370K), DeltaH(not equal) =79.1 +/-6.0 kcal/mol and DeltaS(not equal) =8 +/- 20 J/Kmol; (III) 2 - [N - Acetyl - N - (2-nitrobenzyl)amino]benzylacetate DeltaG(not equal) =80.8 +/-2.0 kJ/mol (380K), DeltaH(not equal) =60.7 +/-6.0 kcal/mol and DeltaS(not equal) =53 +/- 20 J/Kmol; (IV) 2-[N-Acetyl-N-(2-acetyloxybenzyl)amino]phenylacetate DeltaG(not equal) =77.0 +/-2.0 kJ/mol (370K), DeltaH(not equal) =65.3 +/-6.0 kJ/mol and DeltaS(not equal) =-32 +/- 20 J/Kmol. Substitution at positions 2 and 2' with bulky groups appears to be essential to freeze the gauche structure at room temperature and consequently, the main contribution to the barrier arises from the steric hindrance between these two groups. Structure I shows an anomalous behavior...

The Spitzer Survey of Stellar Structure in Galaxies (S$^4$G): Precise Stellar Mass Distributions from Automated Dust Correction at 3.6 microns

Querejeta, M.; Meidt, S. E.; Schinnerer, E.; Cisternas, M.; Muñoz-Mateos, J. C.; Sheth, K.; Knapen, J.; van de Ven, G.; Norris, M. A.; Peletier, R.; Laurikainen, E.; Salo, H.; Holwerda, B. W.; Athanassoula, E.; Bosma, A.; Groves, B.; Ho, L. C.; Gadotti,
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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The mid-infrared is an optimal window to trace stellar mass in nearby galaxies and the 3.6$\mu m$ IRAC band has been exploited to this effect, but such mass estimates can be biased by dust emission. We present our pipeline to reveal the old stellar flux at 3.6$\mu m$ and obtain stellar mass maps for more than 1600 galaxies available from the Spitzer Survey of Stellar Structure in Galaxies (S$^{4}$G). This survey consists of images in two infrared bands (3.6 and 4.5$\mu m$), and we use the Independent Component Analysis (ICA) method presented in Meidt et al. (2012) to separate the dominant light from old stars and the dust emission that can significantly contribute to the observed 3.6$\mu m$ flux. We exclude from our ICA analysis galaxies with low signal-to-noise ratio (S/N < 10) and those with original [3.6]-[4.5] colors compatible with an old stellar population, indicative of little dust emission (mostly early Hubble types, which can directly provide good mass maps). For the remaining 1251 galaxies to which ICA was successfully applied, we find that as much as 10-30% of the total light at 3.6$\mu m$ typically originates from dust, and locally it can reach even higher values. This contamination fraction shows a correlation with specific star formation rates...

Four IRAC Sources with an Extremely Red H-[3.6] Color: Passive or Dusty Galaxies at z>4.5?

Huang, J. -S.; Zheng, X. Z.; Rigopoulou, D.; Magdis, G.; Fazio, G. G.; Wang, T.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/10/2011 Português
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We report detection of four IRAC sources in the GOODS-South field with an extremely red color of H$-$[3.6]$>$4.5. The four sources are not detected in the deep HST WFC3 H-band image with H$_{limit}$=28.3 mag. We find that only 3 types of SED templates can produce such a red H$-$[3.6] color: a very dusty SED with the Calzetti extinction of A$_V$=16 mag at z=0.8; a very dusty SED with the SMC extinction of A$_V$=8 mag at z=2.0$\sim$2.2; and an 1Gyr SSP with A$_V \sim$0.8 at z=5.7. We argue that these sources are unlikely dusty galaxies at z$\leq$2.2 based on absent strong MIPS 24$\mu$m emission. The old stellar population model at z$>$4.5 remains a possible solution for the 4 sources. At z$>$4.5, these sources have stellar masses of Log(M$_*$/M$_{\odot}$)=10.6$\sim$11.2. One source, ERS-1, is also a type-II X-ray QSO with L$_{2-8keV}$=1.6$\times 10^{44}$ erg s$^{-1}$. One of the four sources is an X-ray QSO and another one is a HyperLIRG, suggesting a galaxy-merging scenario for the formation of these massive galaxies at high redshifts.; Comment: 15 pages, 3 figures, accepted by ApJ Lett

Reconstructing the stellar mass distributions of galaxies using S4G IRAC 3.6 and 4.5 micron images: I. Correcting for contamination by PAH, hot dust, and intermediate age stars

Meidt, Sharon E.; Schinnerer, Eva; Knapen, Johan H.; Bosma, Albert; Athanassoula, E.; Sheth, Kartik; Buta, Ronald J.; Zaritsky, Dennis; Laurikainen, Eija; Elmegreen, Debra; Elmegreen, Bruce G.; Gadotti, Dimitri A.; Salo, Heikki; Regan, Michael; Ho, Luis C
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/10/2011 Português
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With the aim of constructing accurate 2D maps of the stellar mass distribution in nearby galaxies from S4G 3.6 and 4.5 micron images, we report on the separation of the light from old stars from the emission contributed by contaminants (e.g. hot dust and the 3.3 micron PAH feature). Results for a small sample of six disk galaxies (NGC 1566, NGC 2976, NGC 3031, NGC 3184, NGC 4321, and NGC 5194) with a range of morphological properties, dust contents and star formation histories are presented to demonstrate our approach. We use an Independent Component Analysis (ICA) technique designed to separate statistically independent source distributions, maximizing the distinction in the [3.6]-[4.5] colors of the sources. The technique also removes emission from intermediate-age evolved red objects with a low mass-to-light ratio, such as asymptotic giant branch (AGB) and red supergiant (RSG) stars, revealing maps of the underlying old distribution of light with [3.6]-[4.5] colors consistent with the colors of K and M giants. Contaminants are identified via comparison to the non-stellar emission imaged at 8 microns, which is dominated by the broad PAH feature. Using the measured 3.6/8 micron ratio to select the individual contaminants, we find that hot dust and PAH together contribute between ~5-15% to the integrated light at 3.6 microns...

Comparison of 3.6 - 8.0 Micron Spitzer/IRAC Galactic Center Survey Point Sources with Chandra X-Ray Point Sources in the Central 40x40 Parsecs

Arendt, R. G.; Gezari, D. Y.; Stolovy, S. R.; Sellgren, K.; Smith, R.; Ramirez, S. V.; Yusef-Zadeh, F.; Law, C. J.; Smith, H. A.; Cotera, A. S.; Moseley, S. H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 11/06/2008 Português
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We have studied the correlation between 2357 Chandra X-ray point sources in a 40 x 40 parsec field and ~20,000 infrared sources we observed in the corresponding subset of our 2 x 1.4 degree Spitzer/IRAC Galactic Center Survey at 3.6-8.0 um, using various spatial and X-ray hardness thresholds. The correlation was determined for source separations of less than 0.5", 1" or 2". Only the soft X-ray sources show any correlation with infrared point sources on these scales, and that correlation is very weak. The upper limit on hard X-ray sources that have infrared counterparts is <1.7% (3 sigma). However, because of the confusion limit of the IR catalog, we only detect IR sources with absolute magnitudes < ~1. As a result, a stronger correlation with fainter sources cannot be ruled out. Only one compact infrared source, IRS 13, coincides with any of the dozen prominent X-ray emission features in the 3 x 3 parsec region centered on Sgr A*, and the diffuse X-ray and infrared emission around Sgr A* seems to be anti-correlated on a few-arcsecond scale. We compare our results with previous identifications of near-infrared companions to Chandra X-ray sources.; Comment: 28 pages, 8 Postscript figures (low resolution). Accepted for publication in the ApJ

Angular Clustering of Galaxies at 3.6 micron from the SWIRE survey

Oliver, Seb; Waddington, Ian; Gonzalez-Solares, Eduardo; Surace, Jason; Fang, Fan; Shupe, Dave; Jarrett, Tom; Lonsdale, Carol; Xu, Cong Kevin; Farrah, Duncan; Salaman, Malcolm; Rowan-Robinson, Michael; Siana, Brian; Smith, H. E. Gene
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/05/2004 Português
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We present the first analysis of large-scale clustering from the Spitzer Wide-area InfraRed Extragalactic legacy survey: SWIRE. We compute the angular correlation function of galaxies selected to have 3.6 micron fluxes brighter than 32 muJy in three fields totaling two square degrees in area. In each field we detect clustering with a high level of significance. The amplitude and slope of the correlation function is consistent between the three fields and is modeled as $w(theta)=A\theta^{1-\gamma}$ with $A=(0.6\pm0.3)\times10^{-3}, \gamma=2.03\pm0.10$. With a fixed slope of $\gamma=1.8$, we obtain an amplitude of $A=(1.7\pm0.1)\times10^{-3}$. Assuming an equivalent depth of K~18.7 mag we find our errors are smaller but our results are consistent with existing clustering measurements in K-band surveys and with stable clustering models. We estimate our median redshift $z\simeq 0.75$ and this allows us to obtain an estimate of the three-dimensional correlation function $\xi(r)$, for which we find $r_0=4.4\pm0.1 h^{-1}$ Mpc.; Comment: 13 pages, Latex, 3 figs, accepted for ApJS Spitzer Special Edition

Comparison of 3.6-8.0 μm Spitzer/IRAC Galactic Center Survey Point Sources with Chandra X-Ray Point Sources in the Central 40 × 40 Parsecs

Arendt, R. G.; Gezari, D. Y.; Stolovy, S. R.; Sellgren, K.; Smith, R.; Ramírez, S. V.; Yusef-Zadeh, F.; Law, C. J.; Smith, H. A.; Cotera, A. S.; Moseley, S. H.
Fonte: American Astronomical Society Publicador: American Astronomical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 01/10/2008 Português
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We have studied the correlation between 2357 Chandra X-ray point sources in a 40 × 40 pc field and ~20,000 infrared sources we observed in the corresponding subset of our 2° × 1.4° Spitzer/IRAC Galactic Center Survey at 3.6-8.0 μm, using various spatial and X-ray hardness thresholds. The correlation was determined for source separations of less than 0.5", 1", or 2". Only the soft X-ray sources show any correlation with infrared point sources on these scales, and that correlation is very weak. The upper limit on hard X-ray sources that have infrared counterparts is <1.7% (3 σ). However, because of the confusion limit of the IR catalog, we only detect IR sources with absolute magnitudes ≾ 1. As a result, a stronger correlation with fainter sources cannot be ruled out. Only one compact IR source, IRS 13, coincides with any of the dozen prominent X-ray emission features in the 3 × 3 pc region centered on Sgr A^*, and the diffuse X-ray and IR emission around Sgr A^* seems to be anticorrelated on a few-arcsecond scale. We compare our results with previous identifications of near-infrared companions to Chandra X-ray sources.

The Evolution of Dusty Star Formation and Stellar Mass Assembly in Clusters: Results from the IRAC 3.6, 4.5, 5.8, and 8.0 μm Cluster Luminosity Functions

Muzzin, Adam; Wilson, Gillian; Lacy, Mark; Yee, H. K. C.; Stanford, S. A.
Fonte: American Astronomical Society Publicador: American Astronomical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 20/10/2008 Português
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We present a catalog of 99 candidate clusters and groups of galaxies in the redshift range 0.1 < z_(phot) < 1.3 discovered in the Spitzer FLS. The clusters are selected by their R_c − 3.6 μm galaxy color-magnitude relation using the cluster red-sequence algorithm. Using this cluster sample, we compute the 3.6, 4.5, 5.8, and 8.0 μm cluster LFs. Similar to previous studies, we find that for the bands that trace stellar mass at these redshifts (3.6 and 4.5 μm) the evolution in M* is consistent with a passively evolving population of galaxies with a high formation redshift (z_f > 1.5). Using the 3.6 μm LF as a proxy for stellar luminosity, we remove this component from the MIR (5.8 and 8.0 μm ) cluster LFs and measure the LF of dusty star formation/AGNs in clusters. We find that at z < 0.4 the bright end of the cluster 8.0 μm LF is well described by a composite population of quiescent galaxies and regular star-forming galaxies with a mix consistent with typical cluster blue fractions; however, at z > 0.4, an additional population of dusty starburst galaxies is required to properly model the 8.0 μm LFs. Comparison to field studies at similar redshifts shows a strong differential evolution in the field and cluster 8.0 μm LFs with redshift. At z ~ 0.65 8.0 μm -detected galaxies are more abundant in clusters compared to the field...

Synthesis and antimicrobial activity of 2-(aminoacid ester)-3-(6-methyl-2-pyridyl)-3,4-dihydro-2H-1,3,2 λ5-benzoxazaphosphinin-2-thiones

Kumar,M. Anil; Kumar,K. Suresh; Reddy,C. Devendranath; Raju,C. Naga; Reddy,C. Suresh; Krishna,P. Hari
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 Português
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Synthesis of 2-(aminoacid ester)-3-(6-methyl-2-pyridyl)-3,4-dihydro-2H-1,3,2λ5-benzoxazaphosphinin-2-thiones (3a-j) was accomplished through a two-step process. It involves the prior preparation of 2-chloro-3-(6-methyl-2-pyridyl)-3,4-dihydro-2H-1,3,2λ5-benzoxazaphosphinin-2-thione monochloride (2) and its subsequent reaction with the aminoacid ester hydrochlorides in dry tetrahydrofuran-toluene in the presence of triethylamine at various temperatures. These compounds were characterized by IR, ¹H, 13C, 31P NMR and mass spectral data.

Intermolecular interactions and thermodynamic properties of 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide dimers: A density functional theoretical study

Zhao,Ning Ning; Zhao,Ya Ling; Hu,Yin; Ma,Hai Xia; Zhao,Feng Qi; Song,Ji Rong
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2013 Português
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Three fully optimized structures of 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide (LAX-112) dimers have been obtained with the density functional theory (DFT) method at the B3LYP/6-311++G level. Vibrational frequency calculations were carried out to ascertain that each structure is a minimum (no imaginary frequencies). The intermolecular interaction energy is calculated with the basis set superposition error (BSSE) correction and zero point energy (ZPE) correction. The greatest corrected binding energy among the three dimers is -42.38 kJ mol-1. The charge redistribution mainly occurs on the adjacent O(N)......H atoms between submolecules and the charge transfer between two subsystems is very small. Natural bond orbital (NBO) analysis was performed to reveal the origin of the interaction. Based on the vibrational analysis, the standard thermodynamic functions (heat capacities (cºp), entropies (S°m) and enthalpies (H°m)) and the changes of thermodynamic properties from the monomer to dimer with the temperature ranging from 200.00 K to 800.00 K have been obtained using statistical thermodynamics. The results show that the strong hydrogen bonds dominantly contribute to the dimers, while the bonding energies are not only determined by the hydrogen bonding. The dimerization process of dimer II can occur spontaneously at room temperature.