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Biomedical subjects

R Bingham

Publications and source records attributed to R Bingham.

At least 19 recordsLinked to original sources
PubMed2006

Radiation sources based on laser-plasma interactions.

Plasma waves excited by intense laser beams can be harnessed to produce femtosecond duration bunches of electrons with relativistic energies. The very large electrostatic forces of plasma density wakes trailing behind an intense laser pulse provide field potentials capable of accelerating charged particles to high energies over very short distances, as high as 1GeV in a few millimetres. The short length scale of plasma waves provides a means of developing very compact high-energy accelerators, which could form the basis of compact next-generation light sources with unique properties. Tuneable X-ray radiation and particle pulses with durations of the order of or less than 5fs should be possible and would be useful for probing matter on unprecedented time and spatial scales. If developed to fruition this revolutionary technology could reduce the size and cost of light sources by three orders of magnitude and, therefore, provide powerful new tools to a large scientific community. We will discuss how a laser-driven plasma wakefield accelerator can be used to produce radiation with unique characteristics over a very large spectral range.

Journal Article↗
PubMed2006

Using high-power lasers for detection of elastic photon-photon scattering.

The properties of four-wave interaction via the nonlinear quantum vacuum is investigated. The effect of the quantum vacuum is to generate photons with new frequencies and wave vectors, due to elastic photon-photon scattering. An expression for the number of generated photons is derived, and using state-of-the-art laser data it is found that the number of photons can reach detectable levels. In particular, the prospect of using the high-repetition Astra Gemini system at the Rutherford Appleton Laboratory is discussed. The problem of noise sources is reviewed, and it is found that the noise level can be reduced well below the signal level. Thus, detection of elastic photon-photon scattering may for the first time be achieved.

Journal Article↗
PubMed2005

Quasiparticle approach to the modulational instability of drift waves coupling to zonal flows.

The interaction between broadband drift mode turbulence and zonal flows has been studied through the wave-kinetic approach. Simulations have been conducted in which a particle-in-cell representation is used for the quasiparticles, while a fluid model is employed for the plasma. The interactions have been studied in a plasma edge configuration which has applications in both tokamak physics and magnetopause boundary layer studies. Simulation results show the development of a zonal flow through the modulational instability of the drift wave distribution, as well as the existence of solitary zonal flow structures about an ion gyroradius wide, drifting towards steeper relative density gradients.

Journal Article↗
PubMed2005

Efficiency and energy spread in laser-wakefield acceleration.

The theoretical limits on efficiency and energy spread of the laser-wakefield accelerator are investigated using a one-dimensional model. Modifications, both of the wakefield due to the electron bunch, and of the laser pulse shape due to the varying permittivity of the plasma, are described self-consistently. It is found that a short laser pulse gives a higher efficiency than a long laser pulse with the same initial energy. Energy spread can be minimized by optimizing bunch length and bunch charge such that the variation of the accelerating force along the length of the bunch is minimized. An inherent trade-off between energy spread and efficiency exists.

Journal Article↗
PubMed2004

Anaesthetic management in facial bipartition surgery: the experience of one centre.

Facial bipartition is amongst the most radical craniofacial surgery undertaken but is performed rarely. There is little published information on its anaesthetic management. We undertook a retrospective case-note review of 22 consecutive patients undergoing bipartition surgery by the same surgical team in one centre in the period 1993-2001. There were incomplete data for two cases and these were therefore excluded. Patients were aged 2 months to 19 years. Conditions treated were facial cleft (n = 5), frontonasal dysplasia (n = 7) and facial dysostosis (n = 8).Intra-operative complications included major haemorrhage (n = 4), bradycardia (n = 3) and unintentional tracheal extubation (n = 1). There were no peri-operative deaths. All patients required intra-operative blood transfusion and 15% of them had a postoperative haemoglobin concentration > 115% of their pre-operative value. In this series, four patients required postoperative lung ventilation for a median duration of 3 days. Infants < 14 months old were significantly more likely to receive a massive blood transfusion (p = 0.0002), to have an excessively high postoperative haematocrit (p = 0.008) and to require postoperative lung ventilation (p = 0.0002) compared with older patients. We conclude that patients in this age group have a significantly increased risk of postoperative complications.

Adolescent↗
PubMed2003

Resonant quasiparticles in plasma turbulence.

A general view is proposed on wave propagation in fluids and plasmas where the resonant interaction of monochromatic waves with quasiparticles is considered. A kinetic equation for quasiparticles is used to describe the broadband turbulence interacting with monochromatic waves. Resonant interactions occur when the phase velocity of the long wavelength monochromatic wave is nearly equal to the group velocity of short wavelength wave packets, or quasiparticles, associated with the turbulent spectrum. It is shown that quasiparticle Landau damping can take place, as well as quasiparticle beam instabilities, thus establishing a direct link between short and large wavelength perturbations of the medium. This link is distinct from the usual picture of direct and inverse energy cascades, and it can be used as a different paradigm for the fluid and plasma turbulence theories.

Journal Article↗
PubMed2003

Comparison of 0.2% ropivacaine and 0.25% bupivacaine for axillary brachial plexus blocks in paediatric hand surgery.

BACKGROUND: The purpose of this study was to compare the use of ropivacaine 0.2% with bupivacaine 0.25% for axillary brachial plexus block in children undergoing hand surgery. METHODS: In a double-blind, randomized study, 35 children undergoing hand surgery received axillary brachial plexus blocks with 0.5 ml.kg-1 of either 0.2% ropivacaine or 0.25% bupivacaine. Pain scores were noted at 0, 3, 6, 12 and 24 h after surgery. The time to first dose of codeine phosphate and the total doses of all analgesics given were recorded. RESULTS: There was no significant difference between the two groups in pain scores, the time to first dose of codeine phosphate or in analgesic requirements in the first 24 h. CONCLUSIONS: Ropivacaine 0.2% is as effective as bupivacaine 0.25% for axillary brachial plexus blocks in children undergoing hand surgery.

Adolescent↗
PubMed2001

Effect of a magnetic field on the wake potential in a dusty plasma with streaming ions.

The wake potential of a test dust particulate due to an ion cyclotron wave in a dusty plasma with streaming ions is calculated. The role of the external magnetic field on the periodic attractive forces is clarified. The amplitude of wake potential is reduced because the overshielding by streaming ions is inhibited in the presence of the external magnetic field.

Journal Article↗
PubMed2001

Changes in paediatric resuscitation knowledge among doctors.

AIMS: To investigate whether paediatricians have improved their resuscitation knowledge since 1992, and whether those who have attended a paediatric resuscitation course have greater knowledge than those who have not. METHODS: Telephone survey of 94 resident paediatricians admitting emergency cases. Questions on clinical scenarios were asked and adherence to internationally agreed guidelines in answering was determined. RESULTS: There were significantly more correct answers to 9/10 questions in 1999 compared to 1992. The 1999 doctors who had attended a course scored significantly better in 3/10 questions and achieved a higher total score (5.43 versus 4.55). CONCLUSIONS: Knowledge has improved since 1992; this has been over the period in which paediatric resuscitation courses were introduced. In 1999 those who had been on a course were more knowledgeable than those who had not.

Child↗
PubMed2000

The major head protein of bacteriophage T4 binds specifically to elongation factor Tu.

The Lit protease in Escherichia coli K-12 strains induces cell death in response to bacteriophage T4 infection by cleaving translation elongation factor (EF) Tu and shutting down translation. Suicide of the cell is timed to the appearance late in the maturation of the phage of a short peptide sequence in the major head protein, the Gol peptide, which activates proteolysis. In the present work we demonstrate that the Gol peptide binds specifically to domains II and III of EF-Tu, creating the unique substrate for the Lit protease, which then cleaves domain I, the guanine nucleotide binding domain. The conformation of EF-Tu is important for binding and Lit cleavage, because both are sensitive to the identity of the bound nucleotide, with GDP being preferred over GTP. We propose that association of the T4 coat protein with EF-Tu plays a role in phage head assembly but that this association marks infected cells for suicide when Lit is present. Based on these data and recent observations on human immunodeficiency virus type 1 maturation, we speculate that associations between host translation factors and coat proteins may be integral to viral assembly in both prokaryotes and eukaryotes.

Amino Acid Sequence↗
PubMed1998

The adaptive nature of the human neurocognitive architecture: an alternative model.

The model of the human neurocognitive architecture proposed by evolutionary psychologists is based on the presumption that the demands of hunter-gatherer life generated a vast array of cognitive adaptations. Here we present an alternative model. We argue that the problems inherent in the biological markets of ancestral hominids and their mammalian predecessors would have required an adaptively flexible, on-line information-processing system, and would have driven the evolution of a functionally plastic neural substrate, the neocortex, rather than a confederation of evolutionarily prespecified social cognitive adaptations. In alignment with recent neuroscientific evidence, we suggest that human cognitive processes result from the activation of constructed cortical representational networks, which reflect probabilistic relationships between sensory inputs, behavioral responses, and adaptive outcomes. The developmental construction and experiential modification of these networks are mediated by subcortical circuitries that are responsive to the life history regulatory system. As a consequence, these networks are intrinsically adaptively constrained. The theoretical and research implications of this alternative evolutionary model are discussed.

Adaptation, Biological↗