Publications by authors named "Nick Barrett"

6 Publications

  • Page 1 of 1

Design for a high resolution electron energy loss microscope.

Ultramicroscopy 2019 Dec 1;207:112848. Epub 2019 Oct 1.

SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, Gif-sur-Yvette Cedex 91191, France. Electronic address:

An electron optical column has been designed for High Resolution Electron Energy Loss Microscopy (HREELM). The column is composed of electron lenses and a beam separator that are placed between an electron source based on a laser excited cesium atom beam and a time-of-flight (ToF) spectrometer or a hemispherical analyzer (HSA). The instrument will be able to perform full field low energy electron imaging of surfaces with sub-micron spatial resolution and meV energy resolution necessary for the analysis of local vibrational spectra. Thus, non-contact, real space mapping of microscopic variations in vibrational levels will be made possible. A second imaging mode will allow for the mapping of the phonon dispersion relations from microscopic regions defined by an appropriate field aperture.
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December 2019

Sedation with alfentanil versus fentanyl in patients receiving extracorporeal membrane oxygenation: outcomes from a single-centre retrospective study.

Perfusion 2020 03 12;35(2):104-109. Epub 2019 Jul 12.

Pharmacy Department, St Thomas' Hospital, Guys and St Thomas' NHS Foundation Trust, London, UK.

Introduction: In November 2016, our institution switched from alfentanil to fentanyl for analgesia and sedation in adult patients receiving extracorporeal membrane oxygenation. There is no published evidence comparing the use of alfentanil with fentanyl for sedation in extracorporeal membrane oxygenation patients. We conducted a retrospective observational study to explore any significant differences in patient outcomes or in the prescribing of adjunct sedatives before and after the switch.

Methods: Patients were retrospectively identified from a prospectively recorded database of all patients who received extracorporeal membrane oxygenation at our institution between January 2016 and October 2017. Patients included those sedated with alfentanil or fentanyl. The total daily doses of intravenous opioids (alfentanil or fentanyl) were calculated for each patient, and the prescribing of adjunctive sedative or analgesic agents was recorded. Patient demographics, extracorporeal membrane oxygenation modality, clinical outcomes including mortality and length of intensive care and hospital stay were recorded.

Results: A total of 174 patients were identified, 69 on alfentanil and 95 on fentanyl. There was no difference found between groups for mode of extracorporeal membrane oxygenation, age, Acute Physiology and Chronic Health Evaluation 2 score (APACHE II) and Charlson score, except for body mass index (p = 0.002). No differences in patient outcomes was observed between groups, although patients in the alfentanil group received a significantly higher median total daily dose of adjuvant sedatives (quetiapine (p = 0.016) and midazolam (p = 0.009)).

Conclusions: No differences in patient outcomes were found between extracorporeal membrane oxygenation patients sedated with alfentanil compared with fentanyl. There was a statistically significant reduction in some adjunctive sedatives in patients managed with a fentanyl-based regimen. Prospective studies are required to confirm these results.
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March 2020

Proficiency-based progression training: an 'end to end' model for decreasing error applied to achievement of effective epidural analgesia during labour: a randomised control study.

BMJ Open 2018 10 15;8(10):e020099. Epub 2018 Oct 15.

The ASSERT Centre, University College Cork, Cork, Ireland.

Background: Training procedural skills using proficiency-based progression (PBP) methodology has consistently resulted in error reduction. We hypothesised that implementation of metric-based PBP training and a valid assessment tool would decrease the failure rate of epidural analgesia during labour when compared to standard simulation-based training.

Methods: Detailed, procedure-specific metrics for labour epidural catheter placement were developed based on carefully elicited expert input. Proficiency was defined using criteria derived from clinical performance of experienced practitioners. A PBP curriculum was developed to train medical personnel on these specific metrics and to eliminate errors in a simulation environment.Seventeen novice anaesthetic trainees were randomly allocated to undergo PBP training (Group P) or simulation only training (Group S). Following training, data from the first 10 labour epidurals performed by each participant were recorded. The primary outcome measure was epidural failure rate.

Results: A total of 74 metrics were developed and validated. The inter-rater reliability (IRR) of the derived assessment tool was 0.88. Of 17 trainees recruited, eight were randomly allocated to group S and six to group P (three trainees did not complete the study). Data from 140 clinical procedures were collected. The incidence of epidural failure was reduced by 54% with PBP training (28.7% in Group S vs 13.3% in Group P, absolute risk reduction 15.4% with 95% CI 2% to 28.8%, p=0.04).

Conclusion: Procedure-specific metrics developed for labour epidural catheter placement discriminated the performance of experts and novices with an IRR of 0.88. Proficiency-based progression training resulted in a lower incidence of epidural failure compared to simulation only training.

Trial Registration Number: NCT02179879. NCT02185079; Post-results.
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October 2018

Severe respiratory failure.

Lancet 2016 11;388(10057):e12

Guy's and St. Thomas' NHS Foundation Trust, Westminster Bridge Road, London, SE1 7EH.

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November 2016

Skin layer of BiFeO(3) single crystals.

Phys Rev Lett 2011 Jun 6;106(23):236101. Epub 2011 Jun 6.

Charles University in Prague, Faculty of Mathematics and Physics, Prague, Czech Republic.

A surface layer ("skin") different from the bulk was found in single crystals of BiFeO(3). Impedance analysis and grazing incidence x-ray diffraction reveal a phase transition at T(*)∼275±5 °C that is confined within the surface of BiFeO(3). X-ray photoelectron spectroscopy and refraction-corrected x-ray diffraction as a function of incidence angle and photon wavelength indicate a reduced electron density and an elongated out-of-plane lattice parameter within a few nanometers of the surface. The skin will affect samples with large surface to volume ratios, as well as devices that rely on interfacial coupling such as exchange bias.
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June 2011

Investigating children's ability to reflect on stored phonological representations: the Silent Deletion of Phonemes Task.

Int J Lang Commun Disord 2010 Jul-Aug;45(4):411-23

Psychology, Curtin Health Innovation Research Institute, Curtin University of Technology, Perth, WA, Australia.

Background: The development of children's speech, language, and literacy skills is considered to build on a robust and intact speech-processing system, with normally functioning skills at all levels of input and output processing, as well as storage. There are a range of tasks available that assess input and output processing skills, however there are few tasks described in the literature that require a child to reflect on and analyse the internal structure of their own phonological representations.

Aims: This paper will describe the development of the Silent Deletion of Phonemes (SDOP) task. This task is designed to assess a child's ability to delete and manipulate sounds silently within their own stored representations while minimizing the impact of any output difficulties.

Methods & Procedures: The SDOP task was presented to 69 typically developing mainstream Year 2 children (aged 7;2-8;1 years) as part of a battery of phonological processing skills and literacy measures.

Outcomes & Results: Scores for the population of typically developing Year 2 children were normally distributed and above a basal level but not approaching ceiling. Performance on the SDOP was significantly correlated with other measures of phonological processing but not a measure of non-verbal ability. It was most highly correlated with the measure of phonological awareness as expected, as both tasks measure awareness of the internal structure of words. However, the SDOP provided more information about the accuracy and specificity of a child's underlying phonological representations. The SDOP explained a significant amount of concurrent variance in both reading and spelling performance beyond the variance accounted for by the predictors that have been used by researchers to date. In combination, the SDOP and rapid-naming measure accounted for 58.8% of variance in performance on the reading measure and 54.4% of variance in spelling performance.

Conclusions & Implications: The SDOP task appears to be a valid and reliable tool to assess the internal structure of a child's stored phonological representations. Profiling phonological representations allows clinicians to explore children's speech-processing skills which may be particularly useful with children with complex literacy difficulties.
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October 2010