The HOTWAXS detector

Bateman, J.E.; Derbyshire, G.E.; Diakun, G.P.; Duxbury, D.M.; Fairclough, J. Patrick A.; Harvey, Ian; Helsby, W.; Lipp, J.; Marsh, A.S.; Salisbury, J.; Sankar, Gopinathan; Spill, E.J.; Stephenson, R.; Terrill, Nicholas J.

doi:10.1016/j.nima.2007.07.006

Cited by 19 publications

(15 citation statements)

References 10 publications

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“…This has been verified experimentally in a test box which enabled the basic characteristics of the modules to be studied in an X-ray sensitive atmosphere. These results are described in [23] which showed that the OSMOND modules had a very similar performance to the HOT-WAXS modules described in [9] and the gain variation from the front to the back of the strips was measured to be within 10%.…”

Section: The Msgc Modulementioning

confidence: 56%

“…The OSMOND detector is a simple re-working of the HOTWAXS X-ray detector [9] and follows precisely the same design logic by re-engineering the containment vessel for the hyperbaric (14 bar proof) operation necessary to provide adequate conversion efficiency from the 3 He partial pressure and to provide sufficient partial pressure of the CF 4 quencher to bring the range in the gas of the conversion reaction products into the same range as that of 10 keV X-rays in the case of HOTWAXS viz. $1 mm.…”

Section: Detector Designmentioning

confidence: 99%

“…$1 mm. The trade-off between detection efficiency and spatial resolution characteristic of the pixellated readout design was thoroughly explored in computer modelling for X-rays [10] and neutrons [8] with experimental results presented in [9] and [11]. The aim of the design is to capitalise on the availability of cheap channel by channel readout to achieve parallel data capture avoiding the rate limitation set by global methods such as a centroid-finding method.…”

Section: Detector Designmentioning

confidence: 99%

“…The OSMOND MSGCs are of the 'pointing anode' design described previously [9]. The lithography allows each anode strip to be angled to point at the target so permitting a long absorption depth without incurring parallax errors.…”

Section: The Msgc Modulementioning

confidence: 99%

“…This 'pointing anode' geometry also gives parallax free detection in an almost identical fashion to the HOTWAXS detector [9]. A programme of work was then undertaken to produce such a detector, called OSMOND (Off Specular MicrOstrip Neutron Detector), and this report will describe the detector design, performance characteristics and the results of the neutron beam tests performed on the CRISP reflectometer.…”

Section: Introductionmentioning

confidence: 99%

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The OSMOND detector

Bateman

Dalgliesh

Duxbury

et al. 2013

Nuclear Instruments and Methods in Physics Research Section A:

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Section: The Msgc Modulementioning

confidence: 56%

Section: Detector Designmentioning

confidence: 99%

Section: Detector Designmentioning

confidence: 99%

Section: The Msgc Modulementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The OSMOND detector

Bateman

Dalgliesh

Duxbury

et al. 2013

Nuclear Instruments and Methods in Physics Research Section A:

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Thermotropic and structural evaluation of the interaction of natural sphingomyelins with cholesterol

Quinn

Wolf²

2009

Biochimica et Biophysica Acta (BBA) - Biomembranes

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The structural transitions in aqueous dispersions of egg-sphingomyelin and bovine brain-sphingomyelin and sphingomyelin co-dispersed with different proportions of cholesterol were compared during temperature scans between 20 degrees and 50 degrees Celsius using small-angle and wide-angle X-ray scattering techniques. The Bragg reflections observed in the small-angle scattering region from pure phospholipids and codispersions of sphingomyelin:cholesterol in molar ratios 80:20 and 50:50 could all be deconvolved using peak fitting methods into two coexisting lamellar structures. Electron density profiles through the unit cell normal to the bilayer plane were calculated to derive bilayer and water layer thicknesses of coexisting structures at 20 degrees and 50 degrees Celsius. Codispersions of sphingomyelin:cholesterol in a molar ratio 60:40 consisted of an apparently homogeneous bilayer structure designated as liquid-ordered phase. Curve fitting analysis of the wide-angle scattering bands were applied to correlate changes in packing arrangements of hydrocarbon in the hydrophobic domain of the bilayer with changes in enthalpy recorded by differential scanning calorimetry. At 20 degrees Celsius the wide-angle scattering bands of both pure sphingomyelins and codispersions of sphingomyelin and cholesterol could be deconvolved into two symmetric components. A sharp component located at a d-spacing of 0.42 nm was assigned to a gel phase in which the hydrocarbon chains are oriented perpendicular to the bilayer plane. A broader symmetric band centered at d-spacings in the region of 0.44 nm was assigned as disordered hydrocarbon in dispersions of pure sphingomyelin and as liquid-ordered phase in codispersions of sphingomyelin and cholesterol. It is concluded from the peak fitting analysis that cholesterol is excluded from gel phases of egg and brain sphingomyelins at 20 degrees Celsius. The gel phases coexist with liquid-ordered phase comprised of egg-sphingomyelin and 27 mol% cholesterol and brain-sphingomyelin and 33 mol% cholesterol, respectively. Correlation of the disappearance of gel phase during heating scans and the enthalpy change recorded by calorimetry in codispersions of sphingomyelin and cholesterol leads to the conclusion that a major contribution to the broadened phase transition endotherm originates from dilution of the cholesterol-rich liquid-ordered phase by mobilization of sphingomyelin from the melting gel phase.

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The role of Mg in the crystallization of monohydrocalcite

Rodríguez-Blanco

Shaw

Bots

et al. 2014

Geochimica et Cosmochimica Acta

139

157

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Monohydrocalcite is a member of the carbonate family which forms in Mg-rich environments at a wide range of Mg Ca ratios Mg aq Ca aq Although found in modern sedimentary deposits and as a product of biomineralization, there is a lack of information about its formation mechanisms and about the role of Mg during its crystallization. In this work we have quantitatively assessed the mechanism of crystallization of monohydrocalcite through in situ synchrotron-based small and wide angle X-ray scattering (SAXS/WAXS) and off-line spectroscopic, microscopic and wet chemical analyses. Monohydrocalcite crystallizes via a 4-stage process beginning with highly supersaturated solutions from which a Mg-bearing, amorphous calcium carbonate (ACC) precursor precipitates. This precursor crystallizes to monohydrocalcite via a nucleation-controlled reaction in stage two, while in stage three it is further aged through Ostwald-ripening at a rate of 1.8±0.1 nm/h1/2. In stage four, a secondary Ostwald ripening process (66.3±4.3 nm/h1/2) coincides with the release of Mg from the monohydrocalcite structure and the concomitant formation of minor hydromagnesite. Our data reveal that monohydrocalcite can accommodate significant amounts of Mg in its structure MgCO and that its Mg content and dehydration temperature are directly proportional to the saturation index for monohydrocalcite (SIMHC) immediately after mixing the stock solutions. However, its crystallite and particle size are inversely proportional to these parameters. At high supersaturations (SIMHC=3.89) nanometer-sized single crystals of monohydrocalcite form, while at low values (SIMHC=2.43) the process leads to low-angle branching spherulites. Many carbonates produced during biomineralization form at similar conditions to most synthetic monohydrocalcites, and thus we hypothesize that some calcite or aragonite deposits found in the geologic record that have formed at high Mg/Ca ratios could be secondary in origin and may have originally formed via a metastable monohydrocalcite intermediate. This manuscript describes an experimental study in which we elucidated the formation mechanism of monohydrocalcite from a poorly-ordered precursor and the role of Mg in its crystallization. Combining in situ synchrotron-based with various off-line laboratory characterizations allowed us to derive complementary quantitative data that explain the monohydrocalcite crystallization via a multiple stage process. School of Earth and EnvironmentWe believe that our paper is of interest to a broad geochemical community and that our results may help explain a number of important biogeochemical processes (including biomineralization and their link to past variations in ocean chemistry).All authors have read and accepted the manuscript in its current format and we all confirm that this paper represents original work from which no part has been published, nor is being considered for publication, elsewhere. Dear Frank, Thank you very much for the comments and suggestions to improve our manuscript.P...

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The HOTWAXS detector

Cited by 19 publications

References 10 publications

The OSMOND detector

The OSMOND detector

Thermotropic and structural evaluation of the interaction of natural sphingomyelins with cholesterol

The role of Mg in the crystallization of monohydrocalcite

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