3,994 research outputs found
The host galaxies of radio-loud AGN: mass dependencies, gas cooling and AGN feedback
The properties of the host galaxies of a well-defined sample of 2215
radio-loud AGN with redshifts 0.03 < z < 0.3, defined from the SDSS, are
investigated. These are predominantly low radio luminosity sources, with 1.4GHz
luminosities of 10^23 to 10^25 W/Hz. The fraction of galaxies that host
radio-loud AGN with L(1.4GHz) > 10^23 W/Hz is a strong function of stellar
mass, rising from nearly zero below a stellar mass of 10^10 Msun to more than
30% at 5x10^11 Msun. The integral radio luminosity function is derived in six
ranges of stellar and black hole mass. Its shape is very similar in all of
these ranges and can be well fitted by a broken power-law. Its normalisation
varies strongly with mass, as M_*^2.5 or M_BH^1.6; this scaling only begins to
break down when the predicted radio-loud fraction exceeds 20-30%. There is no
correlation between radio and emission line luminosities for the radio-loud AGN
in the sample and the probability that a galaxy of given mass is radio-loud is
independent of whether it is optically classified as an AGN. The host galaxies
of the radio-loud AGN have properties similar to those of ordinary galaxies of
the same mass.
All of these findings support the conclusion that the optical AGN and low
radio luminosity AGN phenomena are independent and are triggered by different
physical mechanisms. Intriguingly, the dependence on black hole mass of the
radio-loud AGN fraction mirrors that of the rate at which gas cools from the
hot atmospheres of elliptical galaxies. It is speculated that gas cooling
provides a natural explanation for the origin of the radio-loud AGN activity,
and it is argued that AGN heating could plausibly balance the cooling of the
gas over time. [Abridged]Comment: Accepted for publication in MNRAS. LaTeX, 16 pages. Figure 10 is in
colou
Influence of major mergers on the radio emission of elliptical galaxies
We investigate the influence of major mergers on the radio emission of
elliptical galaxies. We use a complete sample of close pairs, which contains
475 merging and 1828 non-merging paired elliptical galaxies of M_r<-21.5
selected from the Sloan Digital Sky Survey. In addition, a control sample of
2000 isolated field galaxies is used for comparison. We cross-identify the
optical galaxies with the radio surveys of FIRST and NVSS. We find that the
radio fraction of merging paired galaxies is about 6%, which is slightly higher
than the 5% obtained for non-merging paired galaxies, although these values are
consistent with each other owing to the large uncertainty caused by the limited
sample. The radio fraction is twice as that of isolated galaxies, which is less
than 3%. Radio emission of elliptical galaxies is only slightly affected by
major mergers, but predominantly depends on their optical luminosities.
Therefore, merging is not important in triggering the radio emission of
elliptical galaxies.Comment: 5 pages, 5 figures, 1 table, accepted for publication in A&A, minor
change
Luminescent CaTiO3:Yb,Er nanofibers co-conjugated with Rose Bengal and gold nanorods for potential synergistic photodynamic/photothermal therapy
Photodynamic therapy (PDT) and photothermal therapy (PTT) have been explored widely for application
in cancer treatment. In this work, we describe the synthesis of CaTiO3:Yb,Er (CTO) nanofibers
co-conjugated with Rose Bengal (RB) and gold nanorods (AuNRs), which offer the potential for
combined upconversion photoluminescence (UCPL) and enhanced, synergistic PDT and PTT. Based on
this delivery platform, RB and AuNRs served as the PDT and PTT agents, respectively. RB and AuNRs
have strong and well-matched absorption with the green and red emissions of UCPL CTO nanofibers
respectively, hence a single 980 nm continuous wave laser with deep tissue penetration can be
employed to allow PDT and PTT to occur simultaneously. The nanocomposite can effectively convert
the near-infrared (NIR) radiation from the laser into a combination of targeted hyperthermia and
generation of reactive oxygen species (ROS). In comparison with PDT or PTT alone, the combined
PDT/PTT treatment showed significantly enhanced suppression of the viability of Hep G2 cells in vitro,
demonstrating its potential for use in oncology
Education in the interregnum: an evaluation of Zygmunt Baumanâs liquid-turn writing on education
In his liquid-turn writings, Zygmunt Bauman has come to identify liquid\ud
modernity as a period of interregnum. Education has a central role to\ud
play within the contemporary interregnum by opening up a new public\ud
sphere for dialogue. However, the processes of liquefaction manifest\ud
themselves in conditions that severely limit a personâs ability to exercise\ud
their human agency. Bauman provides no indication of how the\ud
educators can escape the processes that limit agency, nor does he\ud
explain how educators can combat the seductive consumerism that\ud
students need to overcome before they can engage in a reconstruction of\ud
the public sphere
Upconversion nanocrystal "armoured' silica fibres with superior photoluminescence for miRNA detection
We have fabricated a flexible membrane, consisting of SiO2 nanofibres armoured with upconversion nanoparticles, exhibiting intense photoluminescence. These assemblies were subsequently grafted with molecular beacons to produce a biosensor suitable for the detection of specific microRNA and with applications in early cancer detection and point-of-care diagnosis
Measurement of 25Mg(p; gamma)26Al resonance strengths via gamma spectrometry
The COMPTEL instrument performed the first mapping of the 1.809 MeV photons
in the Galaxy, triggering considerable interest in determing the sources of
interstellar 26Al. The predicted 26Al is too low compared to the observation,
for a better understanding more accurate rates for the 25Mg(p; gamma)26Al
reaction are required. The 25Mg(p;gamma)26Al reaction has been investigated at
the resonances at Er= 745; 418; 374; 304 keV at Ruhr-Universitat-Bochum using a
Tandem accelerator and a 4piNaI detector. In addition the resonance at Er = 189
keV has been measured deep underground laboratory at Laboratori Nazionali del
Gran Sasso, exploiting the strong suppression of cosmic background. This low
resonance has been studied with the 400 kV LUNA accelerator and a HPGe
detector. The preliminary results of the resonance strengths will be reported.Comment: Accepted for publication in Journal of Physics
Cancer Patient Experience of Uncertainty While Waiting for Genome Sequencing Results.
There is limited knowledge about cancer patients' experiences of uncertainty while waiting for genome sequencing results, and whether prolonged uncertainty contributes to psychological factors in this context. To investigate uncertainty in patients with a cancer of likely hereditary origin while waiting for genome sequencing results, we collected questionnaire and interview data at baseline, and at three and 12 months follow up (prior to receiving results). Participants (N = 353) had negative attitudes towards uncertainty (M = 4.03, SD 0.68) at baseline, and low levels of uncertainty at three (M = 8.23, SD 7.37) and 12 months (M = 7.95, SD 7.64). Uncertainty about genome sequencing did not change significantly over time [t(210) = 0.660, p = 0.510]. Greater perceived susceptibility for cancer [r(348) = 0.14, p < 0.01], fear of cancer recurrence [r(348) = 0.19, p < 0.01], perceived importance of genome sequencing [r(350) = 0.24, p < 0.01], intention to change behavior if a gene variant indicating risk is found [r(349) = 0.29, p < 0.01], perceived ability to cope with results [r(349) = 0.36, p < 0.01], and satisfaction with decision to have genome sequencing [r(350) = 0.52, p < 0.01] were significantly correlated with negative attitudes towards uncertainty at baseline. Multiple primary cancer diagnoses [B = -2.364 [-4.238, -0.491], p = 0.014], lower perceived ability to cope with results [B = -0.1.881 [-3.403, -0.359], p = 0.016] at baseline, greater anxiety about genome sequencing (avoidance) [B = 0.347 [0.148, 0.546], p = 0.0012] at 3 months, and greater perceived uncertainty about genome sequencing [B = 0.494 [0.267, 0.721] p = 0.000] at 3 months significantly predicted greater perceived uncertainty about genome sequencing at 12 months. Greater perceived uncertainty about genome sequencing at 3 months significantly predicted greater anxiety (avoidance) about genome sequencing at 12 months [B = 0.291 [0.072, 0.509], p = 0.009]. Semi-structured interviews revealed that while participants were motivated to pursue genome sequencing as a strategy to reduce their illness and risk uncertainty, genome sequencing generated additional practical, scientific and personal uncertainties. Some uncertainties were consistently discussed over the 12 months, while others emerged over time. Similarly, some uncertainty coping strategies were consistent over time, while others emerged while patients waited for their genome sequencing results. This study demonstrates the complexity of uncertainty generated by genome sequencing for cancer patients and provides further support for the inter-relationship between uncertainty and anxiety. Helping patients manage their uncertainty may ameliorate psychological morbidity
Gold nanorod-assembled ZnGa2O4:Cr nanofibers for LED-amplified gene silencing in cancer cells
Nanoparticles are now commonly used as non-viral gene vectors for RNA interference (RNAi) in cancer therapy but suffer from low targeting efficiency in situ. Meanwhile, localized drug delivery systems do not offer the effective capability for intracellular gene transportation. We describe here the design and synthesis of a localized therapeutic system, consisting of gold nanorods (Au NRs) loaded with hTERT siRNA assembled on the surface of ZnGa2O4:Cr (ZGOC) nanofibers. This composite system offers the potential for a LED-induced mild photothermal effect which enhances the phagocytosis of Au NRs carrying siRNA and the subsequent release of siRNA in the cytoplasm. Both phenomena amplify the gene silencing effect and consequently offer the potential for a superior therapeutic outcome
High-resolution images of five radio quasars at early cosmological epochs
Context: Until now, there have only been seven quasars at z>4.5 whose the
high-resolution radio structure had been studied in detail with Very Long
Baseline Interferometry (VLBI) imaging. Aims: We almost double the number of
VLBI-imaged quasars at these high redshifts with the aim of studying their
redshift-dependent structural and physical properties in a larger sample.
Methods: We observed five radio quasars (J0813+3508, J1146+4037, J1242+5422,
J1611+0844, and J1659+2101) at 4.5<z<5 with the European VLBI Network (EVN) at
1.6 GHz on 29 October 2008 and at 5 GHz on 22 October 2008. The angular
resolution achieved ranges from 1.5 to 25 milli-arcseconds (mas), depending on
the observing frequency, the position angle in the sky, and the source's
celestial position. Results: The sources are all somewhat extended on mas
scales, but compact enough to be detected at both frequencies. With one
exception of a flat-spectrum source (J1611+0844), their compact emission is
characterised by a steep radio spectrum. We found no evidence of
Doppler-boosted radio emission in the quasars in our sample. The radio
structure of one of them (J0813+3508) is extended to ~7", which corresponds to
43 kpc projected linear size. Many of the highest redshift compact radio
sources are likely to be young, evolving objects, far-away cousins of the
powerful gigahertz peaked-spectrum (GPS) and compact steep-spectrum (CSS)
sources that populate the Universe at lower redshifts.Comment: 7 pages, 2 figures, accepted for Astronomy & Astrophysic
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