| 319491. |
- Henderson, M., et al.
(författare)
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Lifetimes of the 5d ^{9} 6p levels in Hg III
- 1999
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 59:5, s. 4068-4070
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Tidskriftsartikel (refereegranskat)abstract
- We report measurements and theoretical calculations for the lifetimes of the 5d96p levels in Hg iii with J=0,2,3,4. This is an extension of earlier measurements of the lifetimes of the 5d96p levels in Hg iii with J=1, and now provides data for all 12 of the levels. The results also provide an isoelectronic comparison with earlier studies of these levels in Au ii of the Pt sequence, and a homologous comparison with earlier studies of the 4d95p levels in Ag ii, Cd iii, and In iv in the Pd sequence.
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| 319492. |
- Henderson, M, et al.
(författare)
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Lifetimes of the 5d(9)6p levels in HgIII
- 1999
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 59:5, s. 4068-4070
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Tidskriftsartikel (refereegranskat)abstract
- We report measurements and theoretical calculations for the lifetimes of the 5d(9)6p levels in Hg nr with J = 0,2,3,4. This is an extension of earlier measurements of the lifetimes of the 5d(9)6p levels in Hg III with J = 1, and now provides data for all 12 of the levels. The results also provide an isoelectronic comparison with earlier studies of these levels in Au II of the Pt sequence, and a homologous comparison with earlier studies of the 4d(9)5p levels in Ag II, Cd III, and In IV in the Pd sequence. [S1050-2947(99)10905-3].
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| 319493. |
- Henderson, Neil C., et al.
(författare)
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Targeting of alpha(v) integrin identifies a core molecular pathway that regulates fibrosis in several organs
- 2013
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Ingår i: Nature Medicine. - : Springer Science and Business Media LLC. - 1078-8956 .- 1546-170X. ; 19:12, s. 1617-1624
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Tidskriftsartikel (refereegranskat)abstract
- Myofibroblasts are the major source of extracellular matrix components that accumulate during tissue fibrosis, and hepatic stellate cells (HSCs) are believed to be the major source of myofibroblasts in the liver. To date, robust systems to genetically manipulate these cells have not been developed. We report that Cre under control of the promoter of Pdgfrb (Pdgfrb-Cre) inactivates loxP-flanked genes in mouse HSCs with high efficiency. We used this system to delete the gene encoding alpha(v) integrin subunit because various alpha(v)-containing integrins have been suggested as central mediators of fibrosis in multiple organs. Such depletion protected mice from carbon tetrachloride-induced hepatic fibrosis, whereas global loss of beta(3), beta(5) or beta(6) integrins or conditional loss of beta(8) integrins in HSCs did not. We also found that Pdgfrb-Cre effectively targeted myofibroblasts in multiple organs, and depletion of the alpha(v) integrin subunit using this system was protective in other models of organ fibrosis, including pulmonary and renal fibrosis. Pharmacological blockade of alpha(v)-containing integrins by a small molecule (CWHM 12) attenuated both liver and lung fibrosis, including in a therapeutic manner. These data identify a core pathway that regulates fibrosis and suggest that pharmacological targeting of all alpha(v) integrins may have clinical utility in the treatment of patients with a broad range of fibrotic diseases.
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| 319494. |
- Henderson, Pamela, et al.
(författare)
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In-situ fireside corrosion testing of superheater materials with coal, wood and straw fuels for conventional and asvanced steam temperatures
- 2005
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Ingår i: VGB PowerTech. - Essen, Germany : VGB PowerTech eV. - 1435-3199. ; 84:6, s. 53-59
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Tidskriftsartikel (refereegranskat)abstract
- An increase in the steam temperature of a power station increases the electrical efficiency of the turbine. This in turn leads to a reduction in the cost of electricity and in environmental emissions produced per unit of electricity generated. However, higher steam temperatures give rise to more aggressive corrosive environments and the choice of material becomes more important. In addition, the aggressiveness of the fuels also depends on their chemical compositions. As part of a European research programme (COST 522) fireside corrosion tests of superheater and waterwall materials have been performed in-situ in industrial boilers or combustion test facilities, simulating conventional and higher steam temperatures. The fuels used were, straw, wood (logging residues) and coal. Goals were set at different maximum steam temperatures and lifetimes according to the fuel. The targets were: coal 650°C/100,000 h, wood 580°C/40,000 h and straw 580°C/20,000 h .A wide range of materials was tested. An overriding constraint was that the materials must be economically viable and not impose exceptional fabrication requirements. Some materials were tested in a number of combustion environments, allowing useful comparisons to be made. The results showed that for a given superheater alloy, temperature and fuel, the corrosion rate depended on the alloy’s position in a superheater bank. Tubes on the outside, exposed to the flue gas, corroded faster than those positioned deeper in a bank. Tubes experiencing a greater heat flux will corrode more rapidly. Poorly controlled combustion will also increase corrosion. Straw was much more corrosive than wood (logging residues). The difference in corrosiveness increased with increasing temperature above a metal temperature of about 520°C. The corrosion rates of the alloys tested during wood-firing were only a little higher than those from firing coal with a medium to high chlorine content. Straw and wood are often collectively known as “biomass”, but the corrosion they cause can vary by a factor of 5 or more. No difference could be found in the fireside corrosion rates of the steels TP 347H and TP 347HFG, when tested under similar conditions. Esshete 1250 also showed similar fireside corrosion rates to347 instraw and wood boilers and at temperatures below 650°Cin coal boilers. Several alloys were identified to resist corrosion in coal-fired plant at metal temperatures of680°C(steam temperatures650°C) and high heat fluxes. Adequate high temperature creep strength remains more problematic. At lower heat fluxes (resulting in lower corrosion rates) more candidate alloys exist. It is expected that the goals set can be achieved with the use of suitable alloys in the case of wood, waste and coal. For wood (logging residues) TP347, Esshete 1250 and 50Ni50Cr coatings showed sufficient corrosion resistance at the target temperatures. In the coal case HR3C fulfills the requirements of strength and corrosion resistance with a high heat flux and Super 304H and SAVE 25 if the heat flux is low. HR11N and IN671 are suitable for use as claddings on a substrate with the appropriate creep strength. The goal set for straw firing was ambitious, a steam temperature of580°C, and in this case a combination of material, combustion technology and boiler design are needed.
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| 319495. |
- Henderson, Pamela, et al.
(författare)
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Reducing superheater corrosion in wood-fired boilers
- 2006
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Ingår i: Materials and corrosion - Werkstoffe und Korrosion. - : Wiley-VCH Verlagsgesellschaft. - 0947-5117 .- 1521-4176. ; 57:2, s. 128-134
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Tidskriftsartikel (refereegranskat)abstract
- One of the major drawbacks to the combustion of 100% biomass in power station boilers is the increase in the fouling and corrosion of superheaters. Experience shows that conventional superheater steels last no more than 20 000 h or four operating years before they must be replaced, if 100% wood-based fuel is used and the steam temperature is higher than 480C. Rapid corrosion of superheaters leads to increased maintenance costs while widespread deposit formation gives rise to a decrease in efficiency of the turbine and an increase in unplanned outages. This paper reports on measures taken to reduce superheater corrosion. Most biomass fuels have a high content of alkali metals and chlorine, but they contain very little sulphur compared to fossil fuels. Potassium chloride, KCl, is found in the gas phase, condenses on the superheater tubes and forms complex alkali salts with iron and other elements in the steels. These salts have low melting points and are very corrosive. The corrosion can be mitigated by use of an instrument for in-situ measurement of alkali chlorides in the flue gases, in combination with the addition of ammonium sulphate. An ammonium sulphate solution, specially developed for the reduction of corrosion was sprayed into the flue gases and effectively converted KCl into potassium sulphate, K2SO4, much less corrosive than KCl. Deposit probe tests and long-term corrosion probe tests have been performed in-situ in two biomass-fired fluidised bed boilers. One boiler, 105 MW tot, 540C steam, is the CHP plant in Nyköping,Sweden. The other producing 98 MWtot, 480C steam, is a bark-fired boiler at a pulp and paper mill in Munksund, also in Sweden. Tests have been performed with a range of steel types, ferritic and austenitic, with ammonium sulphate additive and under normal conditions (no additive). Corrosion rates have been measured, deposit chemistry analysed and flue gas chemistry and KCl content measured. The structure and composition of the oxide with and without ammonium sulphate has been investigated. The results show that ammonium sulphate reduced the KCl levels in the flue gases, removed the chlorides from the deposits and the metal/oxide interface, greatly reduced the deposition rates and halved the corrosion rates for superheater materials. The alkali chloride measuring system and the use of ammonium sulphate for the reduction of corrosion have now been patented.
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| 319496. |
- Henderson, Pamela, et al.
(författare)
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The use of fuel additives in wood and waste wood fired boilers to reduce corrosion and fouling problems
- 2004
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Ingår i: VGB PowerTech. - Essen : VGB PowerTech e.V.. - 1435-3199. ; 84:6, s. 58-62
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Tidskriftsartikel (refereegranskat)abstract
- One of the major drawbacks to the implementation of 100% biomass in conventional power station boilers is the increase in the fouling and corrosion of superheaters. Rapid corrosion of superheaters leads to increased maintenance costs while fouling caused by widespread deposit formation gives rise to a decrease in efficiency of the turbine and an increase in unplanned outages. The purpose of this paper is to report on the effects of fuel additives to change the biofuel chemistry, thus making the fuel less problematic and reducing corrosion and fouling problems. Full-scale trials have been carried out in 35MWth and 105 MWth combined heat and power stations. Most biomass fuels have a high content of alkali metals and sometimes high chlorine levels, but they contain very little sulphur compared to fossil fuels. It is thought that the addition of sulphur to the fuel could help to reduce corrosion since a deposit containing only alkali sulphates has a higher first melting point than deposits containing alkali chlorides. Molten phases increase the corrosion and fouling rates and in this sense, sulphates are preferred to chlorides in the deposits. To investigate the effect fuel additives, trials were initially performed in a 35 MWth wood-fired circulating fluidised bed boiler, adding controlled amounts of sulphur and a newly developed compound additive, called ChlorOut, to the 100% wood fuel feed or flue gases. It was found that the compound additive, ChlorOut, had a greater effect in removing KCl from the flue gases that pure sulphur, whilst having only a marginal effect on the SO2 content of the flue gas and sulphate content and pH of the flue gas condensate. Long term tests with ChlorOut were then repeated in a 105 MWth boiler and in addition corrosion probe testing of superheater steels was performed with and without ChlorOut. The results showed that the ChlorOut additive effectively reduced KCl levels in the flue gas at the superheaters, removed chlorides from the deposits, reduced fouling problems and reduced the corrosion rates by about 50%.
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| 319497. |
- Henderson, Rayetta G., et al.
(författare)
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Inter-laboratory validation of bioaccessibility testing for metals
- 2014
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Ingår i: Regulatory toxicology and pharmacology. - : Elsevier BV. - 0273-2300 .- 1096-0295. ; 70:1, s. 170-181
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Tidskriftsartikel (refereegranskat)abstract
- Bioelution assays are fast, simple alternatives to in vivo testing. In this study, the intra- and inter-laboratory variability in bioaccessibility data generated by bioelution tests were evaluated in synthetic fluids relevant to oral, inhalation, and dermal exposure. Using one defined protocol, five laboratories measured metal release from cobalt oxide, cobalt powder, copper concentrate, Inconel alloy, leaded brass alloy, and nickel sulfate hexahydrate. Standard deviations of repeatability (S-r) and reproducibility (S-R) were used to evaluate the intra- and inter-laboratory variability, respectively. Examination of the s(R):s(r) ratios demonstrated that, while gastric and lysosomal fluids had reasonably good reproducibility, other fluids did not show as good concordance between laboratories. Relative standard deviation (RSD) analysis showed more favorable reproducibility outcomes for some data sets; overall results varied more between- than within-laboratories. RSD analysis of s(r) showed good within-laboratory variability for all conditions except some metals in interstitial fluid. In general, these findings indicate that absolute bioaccessibility results in some biological fluids may vary between different laboratories. However, for most applications, measures of relative bioaccessibility are needed, diminishing the requirement for high inter-laboratory reproducibility in absolute metal releases. The inter-laboratory exercise suggests that the degrees of freedom within the protocol need to be addressed.
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| 319498. |
- Henderson, R.K., et al.
(författare)
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Evaluation of effluent organic matter fouling in ultrafiltration treatment using advanced organic characterisation techniques
- 2011
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Ingår i: Journal of Membrane Science. - : Elsevier BV. - 1873-3123 .- 0376-7388. ; 382:1-2, s. 50-59
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Tidskriftsartikel (refereegranskat)abstract
- Membrane fouling remains an operational challenge in the ultrafiltration (UF) membrane treatment of wastewater effluent and research is on-going to improve understanding of the organic character of foulants. Two advanced organic characterisation techniques that have potential to lend insight into membrane fouling are size exclusion chromatography with organic carbon, UV254 and nitrogen detection (LC-OCD) and fluorescence excitation-emission matrix (EEM) spectroscopy. In this study, UF treatment was undertaken for five tertiary wastewater effluents. The total hydraulic resistance was determined as well as that contributed by foulant layers fractionated by rinsing, backwashing and chemically desorbing. Organic characterisation for UF feed samples, permeates and each foulant layer was then performed using LC-OCD and FEEM spectroscopy with the aim of improving understanding of the character of foulants present in effluent organic matter (EfOM) and to determine the potential for the use of FEEM spectroscopy as a foulant indicator in such systems. It was determined that the biopolymer fraction was most significantly reduced on UF treatment, as anticipated due to its high molecular size. This was supported by the observation that the majority of the foulant layer comprised predominantly protein-enriched biopolymers (38-60% of total foulant layer DOC) that could be removed by rinsing. The resistance attributed to rinsing was directly related to the combined DOC concentration associated with proteins and low molecular weight neutral compounds as defined by LC-OCD analysis. Furthermore, tyrosine-like fluorescence intensity (λex/em=250/304nm) of both the rinsing solutions and UF feed samples showed good correlation with associated hydraulic resistance for EfOM originating from domestic wastewater, suggesting that fluorescence has potential to be used as a foulant indicator for these systems. © 2011 Elsevier B.V.
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| 319499. |
- Henderson, Vicky, et al.
(författare)
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Executive Stock Option Exercise with Full and Partial Information on a Drift Change Point
- 2020
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Ingår i: SIAM Journal on Financial Mathematics. - : Society for Industrial and Applied Mathematics. - 1945-497X. ; 11:4, s. 1007-1062
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the optimal exercise of an American call executive stock option (ESO) written on a stock whose drift parameter falls to a lower value at a change point, an exponentially distributed random time independent of the Brownian motion driving the stock. Two agents, who do not trade the stock, have differing information on the change point and seek to optimally exercise the option by maximizing its discounted payoff under the physical measure. The first agent has full information and observes the change point. The second agent has partial information and filters the change point from price observations. This scenario is designed to mimic the positions of two employees of varying seniority, a fully informed executive and a partially informed less senior employee, each of whom receives an ESO. The partial information scenario yields a model under the observation filtration (F) over cap in which the stock drift becomes a diffusion driven by the innovations process, an (F) over cap Brownian motion also driving the stock under (F) over cap, and the partial information optimal stopping value function has two spatial dimensions. We rigorously characterize the free boundary PDEs for both agents, establish shape and regularity properties of the associated optimal exercise boundaries, and prove the smooth pasting property in both information scenarios, exploiting some stochastic flow ideas to do so in the partial information case. We develop finite difference algorithms to numerically solve both agents' exercise and valuation problems and illustrate that the additional information of the fully informed agent can result in exercise patterns which exploit the information on the change point, lending credence to empirical studies which suggest that privileged information of bad news is a factor leading to early exercise of ESOs prior to poor stock price performance.
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| 319500. |
- Hendersson, Heidi, et al.
(författare)
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New stories for a more conscious, sustainable society: claiming authorship of the climate story
- 2019
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Ingår i: Climatic Change. - : Springer Science and Business Media LLC. - 0165-0009 .- 1573-1480. ; 158, s. 345-359
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Tidskriftsartikel (refereegranskat)abstract
- Sustainability philosophers claim that we are at an impasse of stories, finding ourselves in a blank chapter between the old and the new. The old story, characterized by separation, technological dominance and human superiority over nature, is unfolding in an ecological crisis giving space for a new narrative defined by inter-being, cooperation and balance. It has been put forward that this crisis is climate change, a phenomenon that epitomizes the old, while holding the potential to act as a bridge to the new. Our study shows the benefits of framing climate change as a problem of story and how the dominant story we have told about climate change can be changed. Based on an approach called “Rising strong”, we address the question of how sustainability students relate to the story on climate change, how they conceptualize and situate it within a bigger narrative, and identify barriers and catalysts for authorship. The results show a clear lack of personal authorship, a feeling of disconnection to the climate story and a disbelief in any revolutionary endings, yet still a slight belief in co-authorship. Catalysts that can help to claim back authorship were identified to be positive emotions (e.g., empathy and hope), integral thinking, creation of space for creativity and co-creation. Barriers were scientific rationality and complexity alongside perceived negative emotions, such as shame and self-doubt. One of the most crucial findings was the re-occurring theme of joint engagement for story-transitioning. This point to the urgent need for both increased co-creation as well as the creation of conditions needed to enable people to engage in such processes.
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