Revealing the ultrafast outflow in IRAS 13224-3809 through spectral variability

We present an analysis of the long-term X-ray variability of the extreme narrow-line Seyfert 1 (NLS1) galaxy IRAS 13224-3809 using principal component analysis (PCA) and fractional excess variability (Fvar) spectra to identify model-independent spectral components. We identify a series of variability peaks in both the first PCA component and Fvar spectrum which correspond to the strongest predicted absorption lines from the ultra-fast outflow (UFO) discovered by Parker et al. (2017). We also find higher order PCA components, which correspond to variability of the soft excess and reflection features. The subtle differences between RMS and PCA results argue that the observed flux-dependence of the absorption is due to increased ionization of the gas, rather than changes in column density or covering fraction. This result demonstrates that we can detect outflows from variability alone, and that variability studies of UFOs are an extremely promising avenue for future research

Analysis of Heat Input Effects in Passive Thermographic NDE

The use of digital imaging techniques for analysing and enhancing IR video frames in thermographic NDE [1–6] allows some improvement in resolution of surface temperature contrast. Of equal importance, however, to the magnitude and longevity of the generated contrast is the magnitude and length of the function governing the input heating rate and source impedance [7], In thermogaphic testing the limiting factor is usually the maximum temperature rise (or drop) over a given time span that the heated (cooled) face of the sample can be subjected to without damage occuring. In this study single step and profiled radiative heat pulses have been assessed numerically and experimentally and compared to contact heating (as with a hot liquid in a flexible bag). The detrimental effects of convective and radiative surface heat losses have been examined and their significance to the testing of low and high diffusivity materials assessed. All results presented here are for the two-sided testing configuration although, in principle, the results are applicable to single sided testing also.</p

A global look at X-ray time lags in Seyfert galaxies

X-ray reverberation, where light-travel time delays map out the compact geometry around the inner accretion flow in supermassive black holes, has been discovered in several of the brightest, most variable and well-known Seyfert galaxies. In this work, we expand the study of X-ray reverberation to all Seyfert galaxies in the $\textit{XMM–Newton}$ archive above a nominal rms variability and exposure level (a total of 43 sources). Approximately 50 per cent of sources exhibit iron K reverberation, in that the broad iron K emission line responds to rapid variability in the continuum. We also find that on long time-scales, the hard band emission lags behind the soft band emission in 85 per cent of sources. This ‘low-frequency hard lag’ is likely associated with the coronal emission, and so this result suggests that most sources with X-ray variability show intrinsic variability from the nuclear region. We update the known iron K lag amplitude versus black hole mass relation, and find evidence that the height or extent of the coronal source (as inferred by the reverberation time delay) increases with mass accretion rate.EK thanks Ari Laor for interesting discussions on this work and acknowledges support from the International Space Science Institute. This work is based on observations obtained with XMM–Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. EK thanks the Gates Cambridge Scholarship and the Hubble Fellowship Program. Support for Program number HSTHF2-51360.001-A was provided by NASA through a Hubble Fellowship grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. EK, WNA, and ACF acknowledge support from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 312789, StrongGravity. CSR acknowledges support from NASA under grant NNX14AF86G. EMC gratefully acknowledges support from the National Science Foundation through CAREER award number 1351222

Nondestructive Testing for Environmental Degradation of Adhesive Joints

The work described here is an ultrasonics based experimental study which aims to address the lack of a reliable technique for detecting strength loss in adhesive joints after exposure to hot wet environments. This is manifested as a change in the failure mode of an adhesive system from a cohesive failure in the as-made condition, that is failure through the adhesive, to an adhesive failure, failure between the adhesive and adherend, after exposure to a hot, wet environment. This work has been concerned with the bonding of aluminum using two part epoxy adhesive. The reason for the change in failure mode is thought to lie in changes in the oxide layer which is present between the aluminum and the epoxy. The oxide layer generally has a porous structure into which epoxy can penetrate, forming a micro-composite layer, referred to as the interlayer. It is the detection of changes in this interlayer which present the biggest problem to current N.D.T. techniques for adhesive joints [1]. This is largely a problem of size, the interlayer being typically no larger than a few microns thick, sandwiched between several hundred microns of epoxy and several millimetres of aluminum. It is the need to detect changes in such a thin layer through such a thick layer which presents the biggest problem

X-ray Absorption and Reflection in Active Galactic Nuclei

X-ray spectroscopy offers an opportunity to study the complex mixture of emitting and absorbing components in the circumnuclear regions of active galactic nuclei, and to learn about the accretion process that fuels AGN and the feedback of material to their host galaxies. We describe the spectral signatures that may be studied and review the X-ray spectra and spectral variability of active galaxies, concentrating on progress from recent Chandra, XMM-Newton and Suzaku data for local type 1 AGN. We describe the evidence for absorption covering a wide range of column densities, ionization and dynamics, and discuss the growing evidence for partial-covering absorption from data at energies > 10 keV. Such absorption can also explain the observed X-ray spectral curvature and variability in AGN at lower energies and is likely an important factor in shaping the observed properties of this class of source. Consideration of self-consistent models for local AGN indicates that X-ray spectra likely comprise a combination of absorption and reflection effects from material originating within a few light days of the black hole as well as on larger scales. It is likely that AGN X-ray spectra may be strongly affected by the presence of disk-wind outflows that are expected in systems with high accretion rates, and we describe models that attempt to predict the effects of radiative transfer through such winds, and discuss the prospects for new data to test and address these ideas.Comment: Accepted for publication in the Astronomy and Astrophysics Review. 58 pages, 9 figures. V2 has fixed an error in footnote

Parametric pattern selection in a reaction-diffusion model

We compare spot patterns generated by Turing mechanisms with those generated by replication cascades, in a model one-dimensional reaction-diffusion system. We determine the stability region of spot solutions in parameter space as a function of a natural control parameter (feed-rate) where degenerate patterns with different numbers of spots coexist for a fixed feed-rate. While it is possible to generate identical patterns via both mechanisms, we show that replication cascades lead to a wider choice of pattern profiles that can be selected through a tuning of the feed-rate, exploiting hysteresis and directionality effects of the different pattern pathways

Bright green light treatment of depression for older adults [ISRCTN69400161]

BACKGROUND: Bright white light has been successfully used for the treatment of depression. There is interest in identifying which spectral colors of light are the most efficient in the treatment of depression. It is theorized that green light could decrease the intensity duration of exposure needed. Late Wake Treatment (LWT), sleep deprivation for the last half of one night, is associated with rapid mood improvement which has been sustained by light treatment. Because spectral responsiveness may differ by age, we examined whether green light would provide efficient antidepressant treatment in an elder age group. METHODS: We contrasted one hour of bright green light (1,200 Lux) and one hour of dim red light placebo (<10 Lux) in a randomized treatment trial with depressed elders. Participants were observed in their homes with mood scales, wrist actigraphy and light monitoring. On the day prior to beginning treatment, the participants self-administered LWT. RESULTS: The protocol was completed by 33 subjects who were 59 to 80 years old. Mood improved on average 23% for all subjects, but there were no significant statistical differences between treatment and placebo groups. There were negligible adverse reactions to the bright green light, which was well tolerated. CONCLUSION: Bright green light was not shown to have an antidepressant effect in the age group of this study, but a larger trial with brighter green light might be of value

The remarkable X-ray variability of IRAS 13224-3809 - I. The variability process

We present a detailed X-ray timing analysis of the highly variable NLS1 galaxy, IRAS 13224-3809. The source was recently monitored for 1.5 Ms with XMM-Newton which, combined with 500 ks archival data, makes this the best studied NLS1 galaxy in X-rays to date. We apply standard time- and Fourier-domain in order to understand the underlying variability process. The source flux is not distributed lognormally, as would be expected for accreting sources. The first non-linear rms-flux relation for any accreting source in any waveband is found, with $\mathrm{rms} \propto \mathrm{flux}^{2/3}$. The light curves exhibit significant strong non-stationarity, in addition to that caused by the rms-flux relation, and are fractionally more variable at lower source flux. The power spectrum is estimated down to $\sim 10^{-7}$ Hz and consists of multiple peaked components: a low-frequency break at $\sim 10^{-5}$ Hz, with slope $\alpha < 1$ down to low frequencies; an additional component breaking at $\sim 10^{-3}$ Hz. Using the high-frequency break we estimate the black hole mass $M_\mathrm{BH} = [0.5-2] \times 10^{6} M_{\odot}$, and mass accretion rate in Eddington units, $\dot m_{\rm Edd} \gtrsim 1$. The non-stationarity is manifest in the PSD with the normalisation of the peaked components increasing with decreasing source flux, as well as the low-frequency peak moving to higher frequencies. We also detect a narrow coherent feature in the soft band PSD at $0.7$ mHz, modelled with a Lorentzian the feature has $Q \sim 8$ and an $\mathrm{rms} \sim 3$ %. We discuss the implication of these results for accretion of matter onto black holes

Identification of gene expression changes associated with the initiation of diapause in the brain of the cotton bollworm, Helicoverpa armigera

<p>Abstract</p> <p>Background</p> <p>Diapause, a state of arrested development accompanied by a marked decrease of metabolic rate, helps insects to overcome unfavorable seasons. <it>Helicoverpa armigera </it>(Har) undergoes pupal diapause, but the molecular mechanism of diapause initiation is unclear. Using suppression subtractive hybridization (SSH), we investigated differentially expressed genes in diapause- and nondiapause-destined pupal brains at diapause initiation.</p> <p>Results</p> <p>We constructed two SSH libraries (forward, F and reverse, R) to isolate genes that are up-regulated or down-regulated at diapause initiation. We obtained 194 unique sequences in the F library and 115 unique sequences in the R library. Further, genes expression at the mRNA and protein level in diapause- and nondiapause-destined pupal brains were confirmed by RT-PCR, Northern blot or Western blot analysis. Finally, we classified the genes and predicted their possible roles at diapause initiation.</p> <p>Conclusion</p> <p>Differentially expressed genes at pupal diapause initiation are possibly involved in the regulation of metabolism, energy, stress resistance, signaling pathways, cell cycle, transcription and translation.</p

The First Decade of Science with Chandra and XMM-Newton

NASA's Chandra X-ray Observatory and ESA's XMM-Newton made their first observations one decade ago. The unprecedented and complementary capabilities of these observatories to detect, image, and measure the energy of cosmic X-rays, achieved less than 50 years after the first detection of an extra-solar X-ray source, represent an increase in sensitivity comparable in going from naked-eye observations to the most powerful optical telescopes over the past 400 years! In this review, we highlight some of the many discoveries made by Chandra and XMM-Newton that have transformed 21st century astronomy and briefly discuss prospects for future research.Comment: 8 pages, 10 figures, published in Natur