11,740 research outputs found
Ozonation of cooling tower waters
Continuous ozone injection into water circulating between a cooling tower and heat exchanger with heavy scale deposits inhibits formation of further deposits, promotes flaking of existing deposits, inhibits chemical corrosion and controls algae and bacteria
Photoionization models for extreme Ly 1216 and HeII 1640 ratios in quasar halos, and PopIII vs AGN diagnostics
We explore mechanisms to produce extremely high Ly-alpha/HeII flux ratios, or
to enhance the observed number of Ly-alpha photons per incident ionizing
photon, in extended AGN-photoionized nebulae at high-redshift. Using
photoionization models, we explore the impact of ionization parameter, gas
metallicity, ionizing spectrum, electron energy distribution, and cloud viewing
angle on the relative fluxes of Ly-alpha, HeII and other lines, and on the
observed number of Ly-alpha photons per incident ionizing photon. We find that
low ionization parameter, a relatively soft or filtered ionizing spectrum, low
gas metallicity, kappa-distributed electron energies, or reflection of Ly-alpha
photons by HI can all result in significantly enhanced Ly-alpha relative to
other lines (>10%), with log Ly-alpha/HeII reaching values up to 4.6. In the
cases of low gas metallicity, reflection by HI, or a hard or filtered ionizing
spectrum, the observed number of Ly-alpha photons per incident ionizing photon
is itself significantly enhanced above the nominal Case B value of 0.66 due to
collisional excitation, reaching values up to 5.3 in our 'extreme case' model.
At low gas metallicity (e.g. 0.1 x Solar), the production of Ly-alpha is
predominantly via collisional excitation rather than recombination. In
addition, we find that collisional excitation of Ly-alpha becomes more
efficient if the ionizing continuum is pre-filtered through an optically thin
screen of gas closer to the AGN. We also show that Ly-alpha / HeII ratios of
the z~3.5 quasars studied by Borisova et al. (2016) are consistent with
AGN-photoionization of gas with moderate to low metallicity and/or low
ionization parameter, without requiring exotic ionization/excitation mechanisms
such as strong line-transfer effects. We also present UV-optical diagnostic
diagrams to distinguish between photoionization by Pop III stars and AGN
photoionization.Comment: Accepted for publication in A&A. 14 pages, 9 figures. Abstract
slightly shortened to meet arxiv character limi
Liquid ethylene-propylene copolymers
Oligomers are prepared by heating solid ethylene-propylene rubber in container that retains solid and permits liquid product to flow out as it is formed. Molecular weight and viscosity of liquids can be predetermined by process temperature. Copolymers have low viscosity for given molecular weight
Modulated voltage metastable ionization detector
The output current from a metastable ionization detector (MID) is applied to a modulation voltage circuit. An adjustment is made to balance out the background current, and an output current, above background, is applied to an input of a strip chart recorder. For low level concentrations, i.e., low detected output current, the ionization potential will be at a maximum and the metastable ionization detector will operate at its most sensitive level. When the detected current from the metastable ionization detector increases above a predetermined threshold level, a voltage control circuit is activated which turns on a high voltage transistor which acts to reduce the ionization potential. The ionization potential applied to the metastable ionization detector is then varied so as to maintain the detected signal level constant. The variation in ionization potential is now related to the concentration of the constituent and a representative amplitude is applied to another input of said strip chart recorder
Social pedagogy, music making and adopted children
Social pedagogy has become a common feature of CPD training for staff working with looked after
children and adopted children. Social workers, foster carers and adoptive parents use the characteristic
features of social pedagogical practice to develop meaningful relationships with a young person in care.
Creative elements such as music have been noted to be useful activities in which both parties (children
and support worker) can share a common interest and partake within a joint activity. This article sets
out to examine the way in which a community music project working with adopted children and their
adoptive parents uses social pedagogy and the impact that this may have on the participants. A case
study strategy is used to examine the Loud and Clear adoption family learning project at Sage Gateshead,
through which a multi-methodological approach was used, including interviews and participatory action
research to gather participants’ and facilitators’ narratives of the impacts the sessions and approaches
were having. Furthermore, participatory observations were also undertaken to see at first hand the
social pedagogical approaches that the facilitators were using within sessions. Findings from the study
indicated that having the opportunity to participate in a joint musical activity was key to helping children
and adoptive parents develop their attachments to one another. Similarly, through facilitators providing
opportunities for the group to socialise, adoptive parents were able to develop a support network that they
felt would have been lacking within their lives. Both of these findings indicate the impact of adopting
the common third approach to music making
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