16,199 research outputs found
Surviving Slavery. Mortality at Mesopotamia, a Jamaican sugar estate, 1762 - 1832
We use survival analysis to study the mortality experience of 1111 slaves living on the British West Indian sugar plantation of Mesopotamia for seven decades prior to the Emancipation Act of 1833. Using three different concepts of analysis time and employing non-parametric and semi-parametric models, our results suggest that female slaves first observed under Joseph Foster Barham II's period of ownership (1789-1832) faced an increased hazard of death compared with those first observed during his predecessor's tenure. We find no such relationship for males. We cite as a possible explanation the employment regime operated by Foster Barham II, which allocated increasing numbers of females to gang labour in the cane fields. A G-estimation model used to compensate for the 'healthy worker survivor effect' estimates that continuous exposure to such work reduced survival times by between 20 and 40 per cent. Our findings are compared with previous studies of Mesopotamia and related to the wider literature investigating the roles of fertility and mortality in undermining the sustainability of Caribbean slave populations.
Acidified and ultrafiltered recovered coagulants from water treatment works sludge for removal of phosphorus from wastewater
This study used a range of treated water treatment works sludge options for the removal of phosphorus (P) from primary wastewater. These options included the application of ultrafiltration for recovery of the coagulant from the sludge. The treatment performance and whole life cost (WLC) of the various recovered coagulant (RC) configurations have been considered in relation to fresh ferric sulphate (FFS). Pre-treatment of the sludge with acid followed by removal of organic and particulate contaminants using a 2kD ultrafiltration membrane resulted in a reusable coagulant that closely matched the performance FFS. Unacidified RC showed 53% of the phosphorus removal efficiency of FFS, at a dose of 20 mg/L as Fe and a contact time of 90 min. A longer contact time of 8 h improved performance to 85% of FFS. P removal at the shorter contact time improved to 88% relative to FFS by pre-acidifying the sludge to pH 2, using an acid molar ratio of 5.2:1 mol H+:Fe. Analysis of the removal of P showed that rapid phosphate precipitation accounted for >65% of removal with FFS. However, for the acidified RC a slower adsorption mechanism dominated; this was accelerated at a lower pH. A cost-benefit analysis showed that relative to dosing FFS and disposing waterworks sludge to land, the 20 year WLC was halved by transporting acidified or unacidified sludge up to 80 km for reuse in wastewater treatment. A maximum inter-site distance was determined to be 240 km above the current disposal route at current prices. Further savings could be made if longer contact times were available to allow greater P removal with unacidified RC
Reuse of recovered coagulants in water treatment: An investigation on the effect coagulant purity has on treatment performance
Coagulant recovery offers many potential benefits to water treatment, by reducing chemical demand and waste production. The key obstacle to successful implementation is achieving the same levels of treatment quality and process economics as commercial coagulants.
This study has evaluated the selectivity of pressure-filtration in the role of a low-cost coagulant recovery technology from waterworks sludge. The treatment performance of the purified recovered coagulant was directly compared to fresh and raw recovered coagulants. DOC and turbidity removal by recovered coagulants was close to that of commercial coagulants, indicating that coagulant can be successfully recovered and regenerated by acidifying waterworks sludge. However, performance was less consistent, with a much narrower optimum charge neutralisation window and 10ā30% worse removal performance under optimum conditions. This inferior performance was particularly evident for recovered ferric coagulants. The impact of this was confirmed by measuring THM formation potential and residual metals concentrations, showing 30ā300% higher THMFPs when recovered coagulants were used.
This study confirms that pressure-filtration can be operated on an economically viable basis, in terms of mass flux and fouling. However, the selectivity currently falls short of the purity required for potable treatment, due to incomplete rejection of sludge contaminants
Coagulant recovery and reuse for drinking water treatment
Coagulant recovery and reuse from waterworks sludge has the potential to significantly reduce waste disposal and chemicals usage for water treatment. Drinking water regulations demand purification of recovered coagulant before they can be safely reused, due to the risk of disinfection by-product precursors being recovered from waterworks sludge alongside coagulant metals. While several full-scale separation technologies have proven effective for coagulant purification, none have matched virgin coagulant treatment performance.
This study examines the individual and successive separation performance of several novel and existing ferric coagulant recovery purification technologies to attain virgin coagulant purity levels. The new suggested approach of alkali extraction of dissolved organic compounds (DOC) from waterworks sludge prior to acidic solubilisation of ferric coagulants provided the same 14:1 selectivity ratio (874 mg/L Fe vs. 61 mg/L DOC) to the more established size separation using ultrafiltration (1285 mg/L Fe vs. 91 mg/L DOC). Cation exchange Donnan membranes were also examined: while highly selective (2555 mg/L Fe vs. 29 mg/L DOC, 88:1 selectivity), the low pH of the recovered ferric solution impaired subsequent treatment performance. The application of powdered activated carbon (PAC) to ultrafiltration or alkali pre-treated sludge, dosed at 80 mg/mg DOC, reduced recovered ferric DOC contamination to <1 mg/L but in practice, this option would incur significant costs.
The treatment performance of the purified recovered coagulants was compared to that of virgin reagent with reference to key water quality parameters. Several PAC-polished recovered coagulants provided the same or improved DOC and turbidity removal as virgin coagulant, as well as demonstrating the potential to reduce disinfection byproducts and regulated metals to levels comparable to that attained from virgin material
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Individualisation versus the geography of new families
NoAccording to leading sociological theorists we have now entered a `late modernĀæ epoch of `de-traditionalisationĀæ and `individualisationĀæ. Families are crucial in this vision, where the social ties of kinship and marriage are weakened, increasingly replaced by the project of self. In this paper we take three geographical indices of central elements of the individualisation thesis, examining the distribution in Britain of same sex couples, births to cohabitants, and mothersĀæ withdrawal from the worker role. Analysis of all three indices give support to two levels of criticism of individualisation theory. First, pre-existing social structures have not gone away; the prevalence and the effect of the components of family form and change examined here seem deeply influenced by pre-existing local structural conditions. Secondly, the analysis supports the criticism that while people might indeed have more room for manoeuvre in late modern society, and may well be less constrained by older traditions, this does not necessarily mean individualisation. The behavioural components of individualisation theory may be a non-sequitor from the observation of changing family forms. We conclude that it seems likely that individualisation may be better conceptualised as one part of pre-existing social and structural processes, and that its behavioural assumptions are unjustified
CCPG1, an unconventional cargo receptor for ER-phagy, maintains pancreatic acinar cell health
ER stress-mediated induction of a new vertebrate-specific autophagy cargo receptor, CCPG1 (cell-cycle progression gene 1), drives degradation of endoplasmic reticulum. CCPG1 acts via ATG8-family interaction and, non-canonically, via discrete interactions with FIP200. CCPG1 ameliorates ER stress in the exocrine pancreas. This has potential implications for inflammation and cancer, discussed here
Recent developments in the application of risk analysis to waste technologies.
The European waste sector is undergoing a period of unprecedented change driven
by business consolidation, new legislation and heightened public and government
scrutiny. One feature is the transition of the sector towards a process industry
with increased pre-treatment of wastes prior to the disposal of residues and the
co-location of technologies at single sites, often also for resource recovery
and residuals management. Waste technologies such as in-vessel composting, the
thermal treatment of clinical waste, the stabilisation of hazardous wastes,
biomass gasification, sludge combustion and the use of wastes as fuel, present
operators and regulators with new challenges as to their safe and
environmentally responsible operation. A second feature of recent change is an
increased regulatory emphasis on public and ecosystem health and the need for
assessments of risk to and from waste installations. Public confidence in waste
management, secured in part through enforcement of the planning and permitting
regimes and sound operational performance, is central to establishing the
infrastructure of new waste technologies. Well-informed risk management plays a
critical role. We discuss recent developments in risk analysis within the sector
and the future needs of risk analysis that are required to respond to the new
waste and resource management agenda
An introduction to the local-to-global behaviour of groups acting on trees and the theory of local action diagrams
The primary tool for analysing groups acting on trees is Bass--Serre Theory.
It is comprised of two parts: a decomposition result, in which an action is
decomposed via a graph of groups, and a construction result, in which graphs of
groups are used to build examples of groups acting on trees. The usefulness of
the latter for constructing new examples of `large' (e.g. nondiscrete) groups
acting on trees is severely limited. There is a pressing need for new examples
of such groups as they play an important role in the theory of locally compact
groups. An alternative `local-to-global' approach to the study of groups acting
on trees has recently emerged, inspired by a paper of Marc Burger and Shahar
Mozes, based on groups that are `universal' with respect to some specified
`local' action. In recent work, the authors of this survey article have
developed a general theory of universal groups of local actions, that behaves,
in many respects, like Bass--Serre Theory. We call this the theory of local
action diagrams. The theory is powerful enough to completely describe all
closed groups of automorphisms of trees that enjoy Tits' Independence Property
(P).
This article is an introductory survey of the local-to-global behaviour of
groups acting on trees and the theory of local action diagrams. The article
contains many ideas for future research projects.Comment: Survey article based on Simon M Smith's lecture at Groups St Andrews
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Mathematical and computer modeling of electro-optic systems using a generic modeling approach
The conventional approach to modelling electro-optic sensor systems is to develop separate models for individual systems or classes of system, depending on the detector technology employed in the sensor and the application. However, this ignores commonality in design and in components of these systems. A generic approach is presented for modelling a variety of sensor systems operating in the infrared waveband that also allows systems to be modelled with different levels of detail and at different stages of the product lifecycle. The provision of different model types (parametric and image-flow descriptions) within the generic framework can allow valuable insights to be gained
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