4,094 research outputs found
Local Luminous Infrared Galaxies. III. Co-evolution of Black Hole Growth and Star Formation Activity?
Local luminous infrared (IR) galaxies (LIRGs) have both high star formation
rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence.
Therefore, they are ideal candidates to explore the co-evolution of black hole
(BH) growth and star formation (SF) activity, not necessarily associated with
major mergers. Here, we use Spitzer/IRS spectroscopy of a complete
volume-limited sample of local LIRGs (distances of <78Mpc). We estimate typical
BH masses of 3x10^7 M_sun using [NeIII]15.56micron and optical [OIII]5007A gas
velocity dispersions and literature stellar velocity dispersions. We find that
in a large fraction of local LIRGs the current SFR is taking place not only in
the inner nuclear ~1.5kpc region, as estimated from the nuclear 11.3micron PAH
luminosities, but also in the host galaxy. We next use the ratios between the
SFRs and BH accretion rates (BHAR) to study whether the SF activity and BH
growth are contemporaneous in local LIRGs. On average, local LIRGs have SFR to
BHAR ratios higher than those of optically selected Seyferts of similar AGN
luminosities. However, the majority of the IR-bright galaxies in the RSA
Seyfert sample behave like local LIRGs. Moreover, the AGN incidence tends to be
higher in local LIRGs with the lowest SFRs. All this suggests that in local
LIRGs there is a distinct IR-bright star forming phase taking place prior to
the bulk of the current BH growth (i.e., AGN phase). The latter is reflected
first as a composite and then as a Seyfert, and later as a non-LIRG optically
identified Seyfert nucleus with moderate SF in its host galaxy.Comment: Accepted for publication in Ap
A Fuzzy Logic Inference Approach for the Estimation of the Passengers Flow Demand
This paper presents a new approach that designs the flow of passengers in mass transportation systems in presence of uncertainties. One of the techniques used for the prediction of passenger demand is the origin destination matrices. However, this method is limited to urban areas and rarely to explicit stations. Otherwise, the gravity models based on friction functions can be another alternative; however, it is difficult to fit into practical achievements. Another solution might be the application of artificial intelligence techniques so as to include some intuitive knowledge provided by an expert to predict the flow demand of passengers’ trips in explicit stations. This paper proposes to combine a matrix of origin-destination trips of travel zones, with the intuitive knowledge, applying a fuzzy logic inference approach
Fluorescence Correlation Spectroscopy in Drug Discovery: Study of Alexa532-Endothelin 1 Binding to the Endothelin ETA Receptor to Describe the Pharmacological Profile of Natural Products
Fluorescence correlation spectroscopy and the newly synthesized Alexa532-ET1 were used to study the dynamics of the endothelin ETA receptor-ligand complex alone and under the influence of a semisynthetic selective antagonist and a fungal extract on living A10 cells. Dose-dependent increase of inositol phosphate production was seen for Alexa532-ET1, and its binding was reduced to 8% by the selective endothelin ETA antagonist BQ-123, confirming the specific binding of Alexa532-ET1 to the endothelin ETA receptor. Two different lateral mobilities of the receptor-ligand complexes within the cell membrane were found allowing the discrimination of different states for this complex. BQ-123 showed a strong binding affinity to the “inactive” receptor state characterized by the slow diffusion time constant. A similar effect was observed for the fungal extract, which completely displaced Alexa532-ET1 from its binding to the “inactive” receptor state. These findings suggest that both BQ-123 and the fungal extract act as inverse agonists
A role for the chemokine receptor CCR6 in mammalian sperm motility and chemotaxis
Although recent evidence indicates that several chemokines and defensins, well-known as inflammatory mediators, are expressed in the male and female reproductive tracts, the location and functional significance of chemokine networks in sperm physiology and sperm reproductive tract interactions are poorly understood. To address this deficiency in our knowledge, we examined the expression and function in sperm of CCR6, a receptor common to several chemoattractant peptides, and screened several reproductive tract fluids for the presence of specific ligands. CCR6 protein is present in mouse and human sperm and mainly localized in the sperm tail with other minor patterns in sperm from mice (neck and acrosomal region) and men (neck and midpiece regions). As expected from the protein immunoblotting and immunofluorescence results, mouse Ccr6 mRNA is expressed in the testis. Furthermore, the Defb29 mRNA encoding the CCR6 ligand, β-defensin DEFB29, is expressed at high levels in the epididymis. As determined by protein chip analysis, several chemokines (including some that act through CCR6, such as CCL20/MIP-3α (formerly macrophage inflammatory protein 3α) and protein hormones were present in human follicular fluid, endometrial secretions, and seminal plasma. In functional chemotaxis assays, capacitated human sperm exhibited a directional movement towards CCL20, and displayed modifications in motility parameters. Our data indicate that chemokine ligand/receptor interactions in the male and female genital tracts promote sperm motility and chemotaxis under non-inflammatory conditions. Therefore, some of the physiological reactions mediated by CCR6 ligands in male reproduction extend beyond a pro-inflammatory response and might find application in clinical reproduction and/or contraception.Fil: Caballero Campo, Pedro. Clínica Tambre. Unidad de Reproducción Humana; España. University of California; Estados UnidosFil: Buffone, Mariano Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Benencia, Fabián. Ohio University; Estados UnidosFil: Conejo García, José R.. The Wistar Institute; Estados UnidosFil: Rinaudo, Paolo F.. University of California; Estados UnidosFil: Gerton, George L.. University of Pennsylvania; Estados Unido
The evolution of the high-energy cut-off in the X-Ray spectrum of the GX 339-4 across a hard-to-soft transition
We report on X-ray observations of the black-hole candidate GX 339-4 during
its 2006/2007 outburst. The hardness-intensity diagram of all RXTE/PCA data
combined shows a q-shaped track similar to that observed in previous outbursts.
The evolution through the HID suggests that in the early phase of the outburst
the source underwent a sequence of state transitions, from the hard to the soft
state, which is supported by our timing analysis. Broadband (4-200 keV)
spectra, fitted with an exponentially cutoff powerlaw, show that the hard
spectral component steepens during the transition from the hard to the soft
state. The high-energy cutoff decreased monotonically from 120 to 60 keV during
the brightening of the hard state, but increased again to 100 keV during the
softening in the hard intermediate state. In the short-lived soft intermediate
state the cutoff energy was ~ 130 keV, but was no longer detected in the soft
state. This is one of the first times that the high-energy cut-off has been
followed in such detail across several state transitions. We find that in
comparison to several other spectral parameters, the cut-off energy changes
more rapidly, just like the timing properties. The observed behaviour of the
high energy cutoff of GX 339-4 is also similar to that observed with
RXTE-INTEGRAL-Swift during the 2005 outburst of GRO J1655-40. These results
constitute a valuable reference to be considered when testing theoretical
models for the production of the hard component in these systems.Comment: 16 pages, 8 figures, 5 tables, accepted for publication in MNRAS Main
Journa
X-ray reflection in a sample of X-ray bright Ultraluminous X-ray sources
We apply a reflection-based model to the best available XMM-Newton spectra of
X-ray bright UltraLuminous X-ray (ULX) sources (NGC 1313 X-1, NGC 1313 X-2, M
81 X-6, Holmberg IX X-1, NGC 5408 X-1 and Holmberg II X-1). A spectral drop is
apparent in the data of all the sources at energies 6-7 keV. The drop is
interpreted here in terms of relativistically-blurred ionized reflection from
the accretion disk. A soft-excess is also detected from these sources (as
usually found in the spectra of AGN), with emission from O K and Fe L, in the
case of NGC 5408 X-1 and Holmberg II X-1, which can be understood as features
arising from reflection of the disk. Remarkably, ionized disk reflection and
the associated powerlaw continuum provide a good description of the broad-band
spectrum, including the soft-excess. There is no requirement for thermal
emission from the inner disk in the description of the spectra. The black holes
of these systems must then be highly spinning, with a spin close to the maximum
rate of a maximal spinning black hole. The results require the action of strong
light bending in these sources. We suggest that they could be strongly
accreting black holes in which most of the energy is extracted from the flow
magnetically and released above the disc thereby avoiding the conventional
Eddington limit.Comment: Accepted for publication in MNRA
Pharmacognostic evaluation of ten species of medicinal importance of cecropia: current knowledge and therapeutic perspectives
This work covers a systematic review of literature about the genus Cecropia from 1978 to 2020, emphasizing the analysis of 10 of the most relevant species and their associated biological activities. Cecropia is a neotropical genus, which comprises about 61 native species in the American continent where it is known to be part of the traditional medicine of numerous countries. Secondary metabolites described for this genus showed an elevated structural and functional diversity, where polyphenols have been the most abundant. Based on this diversity, Cecropia phytochemicals represent an important source of potential therapeutic agents yet to be exploited. This review also highlights the effectiveness of combining chemometrics and ultra-performance liquid chromatography-tandem mass spectrometry as a novel approach to successfully single out Cecropia species phytochemicals. While the medicinal use of Cecropia species is officially recognized in National Pharmacopoeias and Formularies of several Latin
American countries, it is important to recognize that these phytomedicines are complex mixtures requiring a thorough understanding of their chemical composition and their correlation with biological activities to guarantee their quality, safety, and efficacy
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