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1,097 results on '"McCracken, G."'

1. Filming Enhanced Ionization in an Ultrafast Triatomic Slingshot

Author

Howard, A. J., Britton, M., Streeter, Z. L., Cheng, C., Forbes, R., Reynolds, J. L., Allum, F., McCracken, G. A., Gabalski, I., Lucchese, R. R., McCurdy, C. W., Weinacht, T., and Bucksbaum, P. H.

Subjects
Physics - Chemical Physics, Physics - Atomic Physics, Physics - Optics, Quantum Physics
Abstract

Filming atomic motion within molecules is an active pursuit of molecular physics and quantum chemistry. A promising method is laser-induced Coulomb Explosion Imaging (CEI) where a laser pulse rapidly ionizes many electrons from a molecule, causing the remaining ions to undergo Coulomb repulsion. The ion momenta are used to reconstruct the molecular geometry which is tracked over time (i.e. filmed) by ionizing at an adjustable delay with respect to the start of interatomic motion. Results are distorted, however, by ultrafast motion during the ionizing pulse. We studied this effect in water and filmed the rapid "slingshot" motion that enhances ionization and distorts CEI results. Our investigation uncovered both the geometry and mechanism of the enhancement which may inform CEI experiments in many other polyatomic molecules.

Published
2022

2. Strong Field Ionization of Water: Nuclear Dynamics Revealed by Varying the Pulse Duration

Author

Howard, A. J., Cheng, C., Forbes, R., McCracken, G. A., Mills, W. H., Makhija, V., Spanner, M., Weinacht, T., and Bucksbaum, P. H.

Subjects
Physics - Atomic Physics, Physics - Chemical Physics, Physics - Optics
Abstract

Polyatomic molecules in strong laser fields can undergo substantial nuclear motion within tens of femtoseconds. Ion imaging methods based on dissociation or Coulomb explosion therefore have difficulty faithfully recording the geometry dependence of the field ionization that initiates the dissociation process. Here we compare the strong-field double ionization and subsequent dissociation of water (both H$_2$O and D$_2$O) in 10-fs and 40-fs 800-nm laser pulses. We find that 10-fs pulses turn off before substantial internuclear motion occurs, whereas rapid internuclear motion can take place during the double ionization process for 40-fs pulses. The short-pulse measurements are consistent with a simple tunnel ionization picture, whose predictions help interpret the motion observed in the long-pulse measurements., Comment: 9 pages, 5 figures

Published
2021
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3. Demonstration of quantum entanglement between a single electron spin confined to an InAs quantum dot and a photon

Author

Schaibley, J. R., Burgers, A. P., McCracken, G. A., Duan, L. -M., Berman, P. R., Steel, D. G., Bracker, A. S., Gammon, D., and Sham, L. J.

Subjects
Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The electron spin state of a singly charged semiconductor quantum dot has been shown to form a suitable single qubit for quantum computing architectures with fast gate times. A key challenge in realizing a useful quantum dot quantum computing architecture lies in demonstrating the ability to scale the system to many qubits. In this letter, we report an all optical experimental demonstration of quantum entanglement between a single electron spin confined to single charged semiconductor quantum dot and the polarization state of a photon spontaneously emitted from the quantum dot's excited state. We obtain a lower bound on the fidelity of entanglement of 0.59, which is 84% of the maximum achievable given the timing resolution of available single photon detectors. In future applications, such as measurement based spin-spin entanglement which does not require sub-nanosecond timing resolution, we estimate that this system would enable near ideal performance. The inferred (usable) entanglement generation rate is 3 x 10^3 s^-1. This spin-photon entanglement is the first step to a scalable quantum dot quantum computing architecture relying on photon (flying) qubits to mediate entanglement between distant nodes of a quantum dot network.

Published
2012
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5. Chlorhexidine Or toothpaSte, manual or powered brushing to prevent pNeumonia complicating stroke (CHOSEN): a 2x2 factorial randomised controlled feasibility trial

Author

Smith, C, Lightbody, Catherine Elizabeth, Sandom, F, Jones, E, Gross, C, Clements, I, Westoby, W, Brady, M, McCracken, G, Langhorne, P, Hoare, Z, Watkins, Caroline Leigh, Brocklehurst, P, Smith, C, Lightbody, Catherine Elizabeth, Sandom, F, Jones, E, Gross, C, Clements, I, Westoby, W, Brady, M, McCracken, G, Langhorne, P, Hoare, Z, Watkins, Caroline Leigh, and Brocklehurst, P

Abstract

Introduction: Increasing evidence links poor oral health status, dysphagia and development of stroke-associated pneumonia (SAP). The aim of this study is to determine whether a phase 3, randomised controlled trial of oral healthcare (OHC) to prevent SAP in dysphagic acute stroke patients is feasible. Method: This is a randomised feasibility trial with parallel process evaluation. Using a factorial design, we plan to randomise 120 patients with acute stroke and dysphagia within 24 h of admission to either non-foaming toothpaste v 1% chlorhexidine gel and to either manual v powered brushing. Stroke unit nursing staff will receive standardised training to deliver the OHC treatments. Assessment of feasibility will include recruitment and set-up of sites, recruitment and retention of participants, adherence to allocated OHC treatment, acceptability and tolerability. We will also record incident SAP, antibiotic doses received, length of stay and modified Rankin score at 3 months. In the process evaluation we will focus on implementation of, and fidelity to, the OHC by undertaking focus groups at each site and employing behaviour change techniques to establish an implementation package. Results: The trial commenced on 31st August 2021 at 4 North West hospitals with final 3 month follow-up at the end of March 2023. Conclusion: We will establish whether feasibility progression criteria are met for a phase 3 trial, and whether further piloting is required.

Published
2023

6. Epigenetic patterns in Atlantic herring (Clupea harengus): Temperature and photoperiod as environmental stressors during larval development.

Author

Kho, J., Delgado, M. L., McCracken, G. R., Munden, J., and Ruzzante, D. E.

Subjects
ATLANTIC herring, WILDLIFE conservation, FISH larvae, DNA methylation, FISH spawning, EPIGENETICS, GENETIC regulation
Abstract

Understanding the molecular mechanisms underlying individual responses to environmental changes is crucial for species conservation and management. Pelagic fishes including Atlantic herring (Clupea harengus) are of particular interest because of their key ecological and economic roles and their susceptibility to a changing ocean from global warming. Temperature and photoperiod have been linked with spawning time and location in adult herring, but no study has thus far investigated the role of environmental factors on gene regulation during the vulnerable early developmental stages. Here, we examine DNA methylation patterns of larval herring bred under two temperatures (11°C and 13°C) and photoperiod (6 and 12 h) regimes in a 2 × 2 factorial design. We found consistently high levels of global methylation across all individuals and a decline in global methylation with increased developmental stage that was more pronounced at 13°C (p ≤ 0.007) than at 11°C (p ≥ 0.21). Most of the differentially methylated sites were in exon and promoter regions for genes linked to metabolism and development, some of which were hypermethylated at higher temperature. These results demonstrate the important role of DNA methylation during larval development and suggest that this molecular mechanism might be key in regulating early‐stage responses to environmental stressors in Atlantic herring. [ABSTRACT FROM AUTHOR]

Published
2024
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8. The DITE Tokamak Experiment

Author

Paul, J. W. M., Clark, W. H. M., Cordey, J. G., Fielding, S. J., Gill, R. D., Hugill, J., McCracken, G. M., Start, D. F. H., Stott, P. E., and Wootton, A. J.

Published
1981

29. Comparing scrape-off layer and divertor physics in JET pure He and D discharges

Author

Pitts, R.A., Andrew, P., Andrew, Y., Becoulet, M., Coffey, I., Coster, D., McDonald, D.C., Eich, T., Erents, S.K., Fenstermacher, M.E., Fundamenski, W., Haas, G., Hermann, A., Hidalgo, C., Hillis, D., Huber, A., Ingesson, L.C., Jachmich, S., Kallenbach, A., Korotkov, A., Lawson, K., Lomas, P., Loarer, T., Loarte, A., Matthews, G.F., McCracken, G., Meigs, A., Mertens, Ph., O’Mullane, M., Philipps, V., Porter, G., Pospieszczyk, A., Rapp, J., Reiter, D., Riccardo, V., Saibene, G., Sartori, R., Stamp, M.F., Tsitrone, E., Wischmeier, M., Gafert, J., and Contributors to the EFDA-JET workprogramme

Published
2003
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36. How much is enough? Effects of technical and biological replication on metabarcoding dietary analysis

Author

Mata, V., Rebelo, H., Amorim, F., Mccracken, G., Jarman, Simon, Beja, P., Mata, V., Rebelo, H., Amorim, F., Mccracken, G., Jarman, Simon, and Beja, P.

Abstract

© 2018 John Wiley & Sons Ltd. DNA metabarcoding is increasingly used in dietary studies to estimate diversity, composition and frequency of occurrence of prey items. However, few studies have assessed how technical and biological replication affect the accuracy of diet estimates. This study addresses these issues using the European free-tailed bat Tadarida teniotis, involving high-throughput sequencing of a small fragment of the COI gene in 15 separate faecal pellets and a 15-pellet pool per each of 20 bats. We investigated how diet descriptors were affected by variability among (a) individuals, (b) pellets of each individual and (c) PCRs of each pellet. In addition, we investigated the impact of (d) analysing separate pellets vs. pellet pools. We found that diet diversity estimates increased steadily with the number of pellets analysed per individual, with seven pellets required to detect ~80% of prey species. Most variation in diet composition was associated with differences among individual bats, followed by pellets per individual and PCRs per pellet. The accuracy of frequency of occurrence estimates increased with the number of pellets analysed per bat, with the highest error rates recorded for prey consumed infrequently by many individuals. Pools provided poor estimates of diet diversity and frequency of occurrence, which were comparable to analysing a single pellet per individual, and consistently missed the less common prey items. Overall, our results stress that maximizing biological replication is critical in dietary metabarcoding studies and emphasize that analysing several samples per individual rather than pooled samples produce more accurate results.

Published
2018

40. THE JET PRELIMINARY TRITIUM EXPERIMENT

Author

REBUT, P, ADAMS, J, ALPER, B, ALTMANN, H, ANDERSEN, A, ANDREW, P, ALIARSHAD, S, BAILEY, W, BALET, B, BARABASCHI, P, BARANOV, Y, BARKER, P, BARNSLEY, R, BARONIAN, M, BARTLETT, D, BELL, A, BENALI, G, BERTOLI, P, BERTOLINI, E, BHATNAGAR, V, BICKLEY, A, BOND, D, BONICELLI, T, BOOTH, S, BOSIA, G, BOTMAN, M, BOUCHER, D, BOUCQUEY, P, BRANDON, M, BREGER, P, BRELEN, H, BREWERTON, W, BRINKSCHULTE, H, BROWN, T, BRUSATI, M, BUDD, T, BURES, M, BURTON, P, BUSINARO, T, BUTCHER, P, BUTTGEREIT, H, CALDWELLNICHOLS, C, CAMPBELL, D, CAMPLING, D, CARD, P, CELENTANO, G, CHALLIS, C, CHANKIN, A, CHERUBINI, A, CHIRON, D, CHRISTIANSEN, J, CHUILON, P, CLAESEN, R, CLEMENT, S, CLIPSHAM, E, COAD, J, COFFEY, I, COLTON, A, COMISKEY, M, CONROY, S, COOKE, M, COOPER, S, CORDEY, J, CORE, W, CORRIGAN, G, CORTI, S, COSTLEY, A, COTTRELL, G, COX, M, CRAWLEY, P, DACOSTA, O, DAVIES, N, DAVIES, S, DEBLANK, H, DEESCH, H, DEKOCK, L, DEKSNIS, E, DELIYANAKUS, N, DENNEHINNOV, G, DESCHAMPS, G, DICKSON, W, DIETZ, K, DINES, A, DMITRENKO, S, DMITRIEVA, M, DOBBING, J, DOLGETTA, N, DORLING, S, DOYLE, P, DUCHS, D, DUQUENOY, H, EDWARDS, A, EHRENBERG, J, EKEDAHL, A, ELEVANT, T, ERENTS, S, ERIKSSON, L, FAJEMIROKUN, H, FALTER, H, FREILING, J, FROGER, C, FROISSARD, P, FULLARD, K, GADEBERG, M, GALETSAS, A, GALBIATI, L, GAMBIER, D, GARRIBBA, M, GAZE, P, GIANNELLA, R, GIBSON, A, GILL, R, GIRARD, A, GONDHALEKAR, A, GOODALL, D, GORMEZANO, C, GOTTARDI, N, GOWERS, C, GREEN, B, HAANGE, R, HAIGH, A, HANCOCK, C, HARBOUR, P, HAWKES, N, HAYNES, P, HEMMERICH, J, HENDER, T, HOEKZEMA, J, HORTON, L, HOW, J, HOWARTH, P, HUART, M, HUGHES, T, HUGUET, M, HURD, F, IDA, K, INGRAM, B, IRVING, M, JACQUINOT, J, JAECKEL, H, JAEGER, J, JANESCHITZ, G, JANKOWICZ, Z, JARVIS, O, JENSEN, F, JONES, E, JONES, L, JONES, T, JUNGER, J, JUNIQUE, F, KAYE, A, KEEN, B, KEILHACKER, M, KERNER, W, KIDD, N, KONIG, R, KONSTANTELLOS, A, KUPSCHUS, P, LASSER, R, LAST, J, LAUNDY, B, LAUROTARONI, L, LAWSON, K, LENNHOLM, M, LINGERTAT, J, LITUNOVSKI, R, LOARTE, A, LOBEL, R, LOMAS, P, LOUGHLIN, M, LOWRY, C, MAAS, A, MACKLIN, B, MAGGI, C, MAGYAR, G, MARCHESE, V, MARCUS, F, MART, J, MARTIN, D, MARTIN, E, MARTINSOLIS, R, MASSMANN, P, MATTHEWS, G, MCBRYAN, H, MCCRACKEN, G, MERIGUET, P, MIELE, P, MILLS, S, MILLWARD, P, MINARDI, E, MOHANTI, R, MONDINO, P, MONTVAI, A, MORGAN, P, MORSI, H, MURPHY, G, NAVE, F, NEUDATCHIN, S, NEWBERT, G, NEWMAN, M, NIELSEN, P, NOLL, P, OBERT, W, OBRIEN, D, OROURKE, J, OSTROM, R, OTTAVIANI, M, PAPASTERGIOU, S, PASINI, D, PATEL, B, PEACOCK, A, PEACOCK, N, PEARCE, R, PEARSON, D, PEPEDESILVA, R, PERINIC, G, PERRY, C, PICK, M, PLANCOULAINE, J, POFFE, J, POHLCHEN, R, PORCELLI, F, PORTE, L, PRENTICE, R, PUPPIN, S, PUTVINSKII, S, RADFORD, G, RAIMONDI, T, RAMOSDEANDRADE, M, RAPISARDA, M, REICHLE, R, RICHARDS, S, RIGHI, E, RIMINI, F, ROLFE, A, ROSS, R, ROSSI, L, RUSS, R, SACK, H, SADLER, G, SAIBENE, G, SALANAVE, J, SANAZZARO, G, SANTAGIUSTINA, A, SARTORI, R, SBORCHIA, C, SCHILD, P, SCHMID, M, SCHMIDT, G, SCHROEPF, H, SCHUNKE, B, SCOTT, S, SIBLEY, A, SIMONINI, R, SIPS, A, SMEULDERS, P, SMITH, R, STAMP, M, STANGEBY, P, START, D, STEED, C, STORK, D, STOTT, P, STUBBERFIELD, P, SUMMERS, D, SUMMERS, H, SVENSSON, L, TAGLE, J, TANGA, A, TARONI, A, TERELLA, C, TESINI, A, THOMAS, P, THOMPSON, E, THOMSEN, K, TREVALION, P, TUBBING, B, TIBONE, F, VANDERBEKEN, H, VLASES, G, VONHELLERMANN, M, WADE, T, WALKER, C, WARD, D, WATKINS, M, WATSON, M, WEBER, S, WESSON, J, WIJNANDS, T, WILKS, J, WILSON, D, WINKEL, T, WOLF, R, WONG, D, WOODWARD, C, WYKES, M, YOUNG, I, ZANNELLI, L, ZOLFAGHARI, A, ZULLO, G, and ZWINGMANN, W

Subjects
inorganic chemicals, Jet (fluid), Tokamak, Materials science, Lawson criterion, Joint European Torus, Plasma, Fusion power, Condensed Matter Physics, law.invention, Nuclear physics, Nuclear Energy and Engineering, Deuterium, law, cardiovascular system, Tritium
Abstract

The first tokamak discharges with deuterium-tritium mixtures have been carried out in the Joint European Torus (JET). The main objectives were to produce more than IMW of fusion power in a controlled way, to determine tritium retention in torus systems and to establish effective means of tritium removal. The experiments were undertaken within limits imposed by restrictions on vessel activation and tritium usage. Deuterium plasmas were heated by high power deuterium neutral beams from fourteen sources and fuelled by two neural beam sources injecting tritium. In the best (D-T discharge), the tritium concentration was about 11% at peak performance, when total neutron emission rate was 6.0*1017 s-1, with 1.7 MW of fusion power. The fusion amplification factor QDT was 0.15. With optimum tritium concentration, this pulse would have produced a fusion power approximately=5 MW and nominal QDT=0.46. The same extrapolation for the best pure deuterium discharge gives about 11 MW and a nominal QDT=1.14. Techniques for introducing, tracking, monitoring and recovering tritium were highly effective.

Published
2016

46. Antenatal HIV testing: evaluation of uptake and women's attitudes in a low risk population

Author

McCracken, G., McGeagh, J., and Roberts, R.

Subjects
Pregnancy, Prenatal Diagnosis, Humans, Mass Screening, Female, HIV Infections, Pilot Projects, Northern Ireland, Patient Acceptance of Health Care, Research Article
Abstract

The number of HIV-positive heterosexuals in the UK is increasing, with a resultant increase in the number of pregnant women who are HIV-positive. The benefits of diagnosing an HIV-positive woman antenatally are well established. The Department of Health of England issued guidelines recommending named voluntary antenatal testing, with a view to achieving a maternal diagnosis rate of 90% by December 2002. In Northern Ireland the policy was distributed in 2003. The screening programme in our hospital had an uptake rate of 98.7 %. Responses to a questionnaire to evaluate the process indicate that HIV testing was associated with low levels of anxiety and that patients were well satisfied with the counselling they received.

Published
2004

49. Learning outcomes: Exploring implications of adopting a different level of detail.

Author

Bateman, H. L., McCracken, G. I., Thomason, J. M., and Ellis, J. S.

Subjects
*EDUCATIONAL outcomes, *EDUCATIONAL programs, *LEARNING, *CURRICULUM planning, *QUALITY assurance, *DENTAL students
Abstract

Abstract: Introduction: Outcome‐based programmes provide a framework to support educators and learners in understanding content and end points within taught courses. Management of these outcomes in the Dental Degree at Newcastle University has been a challenge in relation to quality assurance and enhancement, having over 1500 detailed student‐level outcomes (SLO). This research aimed to explore the implications of adopting a more superficial “course” level of outcome (CLO), when reviewed against a reference set of external LO requirements. Materials and methods: A purposive sample of five courses within the undergraduate dental programme was selected. The mapping of both SLOs and CLOs was reviewed in relation to their total number and the mapping connections to the reference outcomes. Results: There was a mean reduction of 79% in outcomes when comparing SLOs to CLOs. The number of mapping connections between CLOs and the reference set reduced in three courses and increased in two, when compared to SLOs. Discussion: From a purely numerical perspective, changing the detail of learning outcomes has led to a change in mapping connections. As the delivered curriculum has remained unchanged, this demonstrates a potential impact of differing interpretations of learning outcomes. Further review of learning outcomes in relation to the domains categorised within the reference outcome document suggested more mapping links were obtained in clinically focused courses than academic or theoretical courses. Conclusion: A demonstrable impact in mapping connections was observed when the detail within the learning outcomes was changed. This has implications for programme leaders in structuring LOs for a curriculum. [ABSTRACT FROM AUTHOR]

Published
2018
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50. Removal of Trace Contaminants from the Air

Author

VICTOR R. DEITZ, DANIEL LILLIAN, HOMER W. CARHART, JOSEPH K. THOMPSON, L. A. FARROW, T. E. GRAEDEL, T. A. WEBER, R. N. LEE, J. M. HALES, D. E. GLOTFELTY, J. H. CARO, DOUGLAS L. SMITH, JACK E. MCCRACKEN, G. H. FIELDING, H. F. BOGARDUS, R. C. CLARK, J. K. THOMPSON, CHARLES H. KEITH, WILLIAM S. MAGEE

Published
1975

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