Ytterbium-doped tantalum pentoxide waveguide lasers

We have demonstrated a Yb:Ta2O5 waveguide laser fabricated by RF magnetron sputtering on oxidised silicon. The waveguide laser was end-pumped with a laser diode at 977 nm and lasing was observed between 1015 and 1020 nm. The launched pump power threshold and slope efficiency were measured to be ~25 mW and 1.78 %, respectively

The Intergenerational Elasticity of Earnings: Exploring the Mechanisms

Using data covering a single cohort's first 55 years of life, we show that most of the intergenerational elasticity of earnings (IGE) is explained by differences in: years of schooling, cognitive skills, investments of parental time and school quality, and family circumstances during childhood. To decompose the fraction of the IGE explained by each of these channels, we implement a multi-level mediation analysis combined with a latent factor framework that accounts for measurement error. Multilevel mediation analysis allows us to assess not only the direct effect of each channel on the IGE, but also its indirect effects working through the other channels, thus providing an in-depth understanding of the link between parents' and children's earnings. Of these channels, we show that the main driver of the IGE is increased levels of parental investments received by children of high income parents early in their lives, which encourages greater cognitive development and lifetime earnings

Effective equations governing an active poroelastic medium

In this work we consider the spatial homogenization of a coupled transport and fluid-structure interaction model, to the end of deriving a system of effective equations describing the flow, elastic deformation, and transport in an active poroelastic medium. The `active' nature of the material results from a morphoelastic response to a chemical stimulant, in which the growth timescale is strongly separated from other elastic timescales. The resulting effective model is broadly relevant to the study of biological tissue growth, geophysical flows (e.g. swelling in coals and clays) and a wide range of industrial applications (e.g. absorbant hygiene products). The key contribution of this work is the derivation of a system of homogenized partial differential equations describing macroscale growth, coupled to transport of solute, that explicitly incorporates details of the structure and dynamics of the microscopic system, and, moreover, admits finite growth and deformation at the pore-scale. The resulting macroscale model comprises a Biot-type system, augmented with additional terms pertaining to growth, coupled to an advection-reaction-diffusion equation. The resultant system of effective equations is then compared to other recent models under a selection of appropriate simplifying asymptotic limits

Cascading failures in networks of heterogeneous node behavior

Variability in the dynamical function of nodes comprising a complex network impacts upon cascading failures that can compromise the network's ability to operate. Node types correspond to sources, sinks or passive conduits of a current ow, applicable to renewable electrical power micro-grids containing a variable number of intermittently operating generators and consumers of power. The resilience to cascading failures of ensembles of synthetic networks with di_erent topology is examined as a function of the edge current carrying capacity and mix of node types, together with exemplar real-world networks. Whilst a network with homogeneous node type can be resilient to failure, one with identical topology but heterogeneous node function can be strongly susceptible to failure. For networks with similar numbers of sources, sinks and passive nodes the mean resilience decreases as networks become more disordered. Nevertheless all network topologies have enhanced regions of resilience, accessible by manipulation of node composition and functionality

The clonal development of vine maple during Douglas-fir stand development in the Coast Range of Oregon

Natural Douglas-fir stand development is the result of many types of disturbance, both natural and management induced. The magnitude and timing of these disturbances have profound effects on the structure and composition of both the overstory and understory plant communities. Vine maple responds to disturbance by basal sprouting, layering, producing seed and establishing seedlings. By means of clonal regeneration and seedling establishment, vine maple is able to maintain its presence from one stand to the next over a wide range of sites. Previous studies on vine maple have not quantified its or growth in relation to the structural changes which occur during stand development and secondary succession in Douglas-fir forests. A knowledge of vine maple clone development is needed to understand the processes of understory development in secondary succession, and to predict the results of thinning and other silvicultural practices in these forests. The objective of this study was to quantify changes in vine maple development in relation to Douglas-fir stand age and density. Also investigated were the effects of layering on clone development in Douglas-fir stands of different ages and under different management regimes. The second segment of this study was to examine layering more closely, in regards to the rate and pattern of root initiations, and the capability of severed stems to root. The clonal development of vine maple was found to be strongly related to stand age, with most developmental changes occurring during the first 50 years of stand development. Basal sprouting and layering are present throughout stand development, with basal sprouting present primarily in early stand development and layering in the later stages. Seed production and seedling establishment are present in all stages of stand development, except during the years immediately following crown closure. Clone regeneration was found to be strongly influenced by cultural practices common to forest management, such as commercial thinning and prescribed fire. These management treatments affect clone regeneration by controlling clone size and forest debris. These treatments also affect the timing of seedling presence and the abundance of seedlings in stands. In order to understand natural forest succession, and to predict the effect of management practices on stand development, it is important to understand how clonal understory plants, such as vine maple, reproduce and grow during different stages of stand development

Stormy weather in 3C 196.1: nuclear outbursts and merger events shape the environment of the hybrid radio galaxy 3C 196.1

We present a multi-wavelength analysis based on archival radio, optical and X-ray data of the complex radio source 3C 196.1, whose host is the brightest cluster galaxy of a $z=0.198$ cluster. HST data show H$\alpha$+[N II] emission aligned with the jet 8.4 GHz radio emission. An H$\alpha$+[N II] filament coincides with the brightest X-ray emission, the northern hotspot. Analysis of the X-ray and radio images reveals cavities located at galactic- and cluster- scales. The galactic-scale cavity is almost devoid of 8.4 GHz radio emission and the south-western H$\alpha$+[N II] emission is bounded (in projection) by this cavity. The outer cavity is co-spatial with the peak of 147 MHz radio emission, and hence we interpret this depression in X-ray surface brightness as being caused by a buoyantly rising bubble originating from an AGN outburst $\sim$280 Myrs ago. A \textit{Chandra} snapshot observation allowed us to constrain the physical parameters of the cluster, which has a cool core with a low central temperature $\sim$2.8 keV, low central entropy index $\sim$13 keV cm$^2$ and a short cooling time of $\sim$500 Myr, which is $<0.05$ of the age of the Universe at this redshift. By fitting jumps in the X-ray density we found Mach numbers between 1.4 and 1.6, consistent with a shock origin. We also found compelling evidence of a past merger, indicated by a morphology reminiscent of gas sloshing in the X-ray residual image. Finally, we computed the pressures, enthalpies $E_{cav}$ and jet powers $P_{jet}$ associated with the cavities: $E_{cav}\sim7\times10^{58}$ erg, $P_{jet}\sim1.9\times10^{44}$ erg s$^{-1}$ for the inner cavity and $E_{cav}\sim3\times10^{60}$ erg, $P_{jet}\sim3.4\times10^{44}$ erg s$^{-1}$ for the outer cavity.Comment: 14 pages, 4 figures, ApJ accepte

Extended X-ray emission in radio galaxies: the peculiar case of 3C 305

Extended X-ray structures are common in Active Galactic Nuclei (AGNs). Here we present the first case of a Compact Steep Spectrum (CSS) radio galaxy, 3C 305, in which the X-ray radiation appears to be associated with the optical emission line region, dominated by the [O III]5007. On the basis of a morphological study, performed using the comparison between the X-rays, the optical and the radio band, we argue that the high energy emission has a thermal nature and it is not directly linked to the radio jet and hotspots of this source. Finally, we discuss the origin of the extended X-ray structure connected with the optical emission line region following two different interpretations: as due to the interaction between matter outflows and shock-heated environment gas, or as due to gas photoionized by nuclear emission.Comment: 5 pages, 2 figures, Accepted for publication in The ApJL Comments: references and affilitations correcte

The MURALES survey II. Presentation of MUSE observations of 20 3C low-z radio galaxies and first results

We present observations of a complete sub-sample of 20 radio galaxies from the Third Cambridge Catalog (3C) with redshift <0.3 obtained from VLT/MUSE optical integral field spectrograph. These data have been obtained as part of the survey MURALES (a MUse RAdio Loud Emission line Snapshot survey) with the main goal of exploring the Active Galactic Nuclei (AGN) feedback process in a sizeable sample of the most powerful radio sources at low redshift. We present the data analysis and, for each source, the resulting emission line images and the 2D gas velocity field. Thanks to their unprecedented depth (the median 3 sigma surface brightness limit in the emission line maps is 6X10^-18 erg s-1 cm-2 arcsec-2, these observations reveal emission line structures extending to several tens of kiloparsec in most objects. In nine sources the gas velocity shows ordered rotation, but in the other cases it is highly complex. 3C sources show a connection between radio morphology and emission line properties. Whereas, in three of the four Fanaroff and Riley Class I radio galaxies (FRIs), the line emission regions are compact, ~1 kpc in size; in all but one of the Class II radiogalaxies FRIIs, we detected large scale structures of ionized gas with a median extent of 17 kpc. Among the FRIIs, those of high and low excitation show extended gas structures with similar morphological properties, suggesting that they both inhabit regions characterized by a rich gaseous environment on kpc scale.Comment: Accepted for publication in A&

FIRST-based survey of Compact Steep Spectrum sources I. MERLIN images of arc-second scale objects

Compact Steep Spectrum (CSS) sources are powerful extragalactic radio sources with angular dimensions of the order of a few arcseconds or less. Such a compactness is apparently linked to the youth of these objects. The majority of CSSs investigated so far have been known since the early 1980s. This paper is the first in a series where we report the results of an observational campaign targeted on a completely new sample of CSSs which are significantly weaker than those investigated before. The ultimate goal of that campaign is to find out how ``weak'' CSSs compare to ``strong'', classical ones, especially with regard to the morphologies. Here we present an analysis of morphological and physical properties of five relatively large sources based on MERLIN observations at 1.6 and 5 GHz.Comment: 8 pages, 7 figures, A&A in pres