Multi-Pulse Laser Wakefield Acceleration: A New Route to Efficient, High-Repetition-Rate Plasma Accelerators and High Flux Radiation Sources

Laser-driven plasma accelerators can generate accelerating gradients three orders of magnitude larger than radio-frequency accelerators and have achieved beam energies above 1 GeV in centimetre long stages. However, the pulse repetition rate and wall-plug efficiency of plasma accelerators is limited by the driving laser to less than approximately 1 Hz and 0.1% respectively. Here we investigate the prospects for exciting the plasma wave with trains of low-energy laser pulses rather than a single high-energy pulse. Resonantly exciting the wakefield in this way would enable the use of different technologies, such as fibre or thin-disc lasers, which are able to operate at multi-kilohertz pulse repetition rates and with wall-plug efficiencies two orders of magnitude higher than current laser systems. We outline the parameters of efficient, GeV-scale, 10-kHz plasma accelerators and show that they could drive compact X-ray sources with average photon fluxes comparable to those of third-generation light source but with significantly improved temporal resolution. Likewise FEL operation could be driven with comparable peak power but with significantly larger repetition rates than extant FELs

Reconstructing nonlinear plasma wakefields using a generalized temporally encoded spectral shifting analysis

We generalize the temporally encoded spectral shifting (TESS) analysis for measuring plasma wakefields using spectral interferometry to dissimilar probe pulses of arbitrary spectral profile and to measuring nonlinear wakefields. We demonstrate that the Gaussian approximation used up until now results in a substantial miscalculation of the wakefield amplitude, by a factor of up to two. A method to accurately measure higher amplitude quasilinear and nonlinear wakefields is suggested, using an extension to the TESS procedure, and we place some limits on its accuracy in these regimes. These extensions and improvements to the analysis demonstrate its potential for rapid and accurate on-shot diagnosis of plasma wakefields, even at low plasma densities

Optimisation-based Framework for Resin Selection Strategies in Biopharmaceutical Purification Process Development

This work addresses rapid resin selection for integrated chromatographic separations when conducted as part of a high-throughput screening (HTS) exercise during the early stages of purification process development. An optimisation-based decision support framework is proposed to process the data generated from microscale experiments in order to identify the best resins to maximise key performance metrics for a biopharmaceutical manufacturing process, such as yield and purity. A multiobjective mixed integer nonlinear programming (MINLP) model is developed and solved using the ε-constraint method. Dinkelbach's algorithm is used to solve the resulting mixed integer linear fractional programming (MILFP) model. The proposed framework is successfully applied to an industrial case study of a process to purify recombinant Fc Fusion protein from low molecular weight and high molecular weight product related impurities, involving two chromatographic steps with 8 and 3 candidate resins for each step, respectively. The computational results show the advantage of the proposed framework in terms of computational efficiency and flexibility. This article is protected by copyright. All rights reserved

High T(sub c) leads for remote sensing applications

Several NASA programs designed to monitor the Earth's atmosphere from space utilize infrared detectors which operate at or below 4.2 K for optimum performance. At present, the detectors are maintained at cryogenic temperatures by a stored volume of liquid helium. These detectors must be electrically linked to amplification electronics data storage instruments maintained at 80 K. The electrical connections over the temperature gradient account for approximately 20% of the total heat load on the Dewar for some systems, accelerating the boil-off of liquid helium cryogen and reducing the operational lifetime of the space-borne instruments. The recent discovery of high temperature superconductors has provided an opportunity to develop electrically conductive, thermally insulating links to bridge this thermal gradient. This paper describes the modelling of the thermal transport properties of thick film, high T(sub c) electrical bridges across a 4.2-80 K temperature gradient and the impact of such devices on a spaceborne remote sensing system

To follow a rule? On frontline clinicians’ understandings and embodiments of hospital-acquired infection prevention and control rules.

This article reports on a study of clinicians’ responses to footage of their enactments of infection prevention and control. The study’s approach was to elicit clinicians’ reflections on and clarifications about the connections among infection control activities and infection control rules, taking into account their awareness, interpretation, and in situ application of those rules. The findings of the study are that clinicians responded to footage of their own IPC practices by articulating previously unheeded tensions and constraints including: infection control rules that were incomplete, undergoing change, and conflicting; material obstructions limiting infection control efforts; and habituated and divergent rule enactments and rule interpretations that were problematic but disregarded. The reflexive process is shown to elicit clinicians’ learning about these complexities as they affect the accomplishment of effective infection control. The process is further shown to strengthen clinicians’ appreciation of infection control as necessitating deliberation to decide what are locally appropriate standards, interpretations, assumptions, habituations and enactments of infection control. The article concludes that clinicians’ ‘practical wisdom’ is unlikely to reach its full potential without video-assisted scrutiny of and deliberation about in situ clinical work. This enables clinicians to anchor their in situ enactments, reasonings and interpretations to local agreements about the intent, applicability, limits and practical enactment of rules. Key words: video-reflexivity, rules, infection control, patient safety, embodied practice, practical wisdom, abductio

Predicting performance of constant flow depth filtration using constant pressure filtration data

This paper describes a method of predicting constant flow filtration capacities using constant pressure datasets collected during the purification of several monoclonal antibodies through depth filtration. The method required characterisation of the fouling mechanism occurring in constant pressure filtration processes by evaluating the best fit of each of the classic and combined theoretical fouling models. The optimised coefficients of the various models were correlated with the corresponding capacities achieved during constant flow operation at the specific pressures performed during constant pressure operation for each centrate. Of the classic and combined fouling models investigated, the Cake-Adsorption fouling model was found to best describe the fouling mechanisms observed for each centrate at the various different pressures investigated. A linear regression model was generated with these coefficients and was shown to predict accurately the capacities at constant flow operation at each pressure. This model was subsequently validated using an additional centrate and accurately predicted the constant flow capacities at three different pressures (0.69, 1.03 and 1.38 bar). The model used the optimised Cake-Adsorption model coefficients that best described the flux decline during constant pressure operation. The proposed method of predicting depth filtration performance proved to be faster than the traditional approach whilst requiring significantly less material, making it particularly attractive for early process development activities

A Prospective Longitudinal Assessment of Medical Records for Diagnostic Substitution among Subjects Diagnosed with a Pervasive Developmental Disorder in the United States

Background: Previously, investigators suggested that diagnostic substitution from other diagnoses, e.g., mental retardation (MR) and/or cerebral palsy (CP) to pervasive developmental disorder (PDD) is a driving factor behind increases in PDD. This study evaluated potential diagnostic substitution among subjects diagnosed with PDD vs MR or CP by examining birth characteristic overlap.Methods: SAS® and StatsDirect software examined medical records for subjects within the Vaccine Safety Datalink (VSD) database who were Health Maintenance Organization (HMO)-enrolled from birth until diagnosed with an International Classification of Disease, 9th revision (ICD-9) outcome of PDD (299.xx, n=84), CP (343.xx, n=300), or MR (317.xx, 318.xx, or 319.xx, n=51).Results: Subjects with PDD had significantly (p<0.01) increased: male/female ratio (PDD=5.5 vs CP=1.5 or MR=1.3), mean age of initial diagnosis in years (PDD=3.13 vs CP=1.09 or MR=1.62), mean gestational age in weeks at birth (PDD=38.73 vs CP=36.20 or MR=34.84), mean birth weight in grams (PDD=3,368 vs CP=2,767 or MR=2,406), and mean Appearance-Pulse-Grimace-Activity-Respiration (APGAR) scores at 1 minute (PDD=7.82 vs CP=6.37 or MR=6.76) and 5 minutes (PDD=8.77 vs CP=7.92 or MR=8.04), as compared to subjects diagnosed with CP or MR.Conclusion: This study suggests diagnostic substitution cannot fully explain increased PDD prevalence during the 1990s within the United States

An innovative approach to strengthening health professionals’ infection control and limiting hospital-acquired infection: video-reflexive ethnography

Objective To strengthen clinicians’ infection control awareness and risk realisation by engaging them in scrutinising footage of their own infection control practices and enabling them to articulate challenges and design improvements. Design and participants Clinicians and patients from selected wards of 2 hospitals in western Sydney. Main outcome measures Evidence of risk realisation and new insights into infection control as articulated during video-reflexive feedback meetings. Results Frontline clinicians identified previously unrecognised infection risks in their own practices and in their team's practices. They also formulated safer ways of dealing with, for example, charts and patient transfers. Conclusions Video-reflexive ethnography enables frontline clinicians to identify infection risks and to design locally tailored solutions for existing risks and emerging ones

Beyond hand hygiene: a qualitative study of the everyday work of preventing cross-contamination in hospital wards

Background Hospital-acquired infections are the most common adverse event for inpatients worldwide. Efforts to prevent microbial cross-contamination currently focus on hand hygiene and use of personal protective equipment (PPE), with variable success. Better understanding is needed of infection prevention and control (IPC) in routine clinical practice. Methods We report on an interventionist video-reflexive ethnography study that explored how healthcare workers performed IPC in three wards in two hospitals in New South Wales, Australia: an intensive care unit and two general surgical wards. We conducted 46 semistructured interviews, 24 weeks of fieldwork (observation and videoing) and 22 reflexive sessions with a total of 177 participants (medical, nursing, allied health, clerical and cleaning staff, and medical and nursing students). We performed a postintervention analysis, using a modified grounded theory approach, to account for the range of IPC practices identified by participants. Results We found that healthcare workers' routine IPC work goes beyond hand hygiene and PPE. It also involves, for instance, the distribution of team members during rounds, the choreography of performing aseptic procedures and moving ‘from clean to dirty’ when examining patients. We account for these practices as the logistical work of moving bodies and objects across boundaries, especially from contaminated to clean/vulnerable spaces, while restricting the movement of micro-organisms through cleaning, applying barriers and buffers, and trajectory planning. Conclusions Attention to the logistics of moving people and objects around healthcare spaces, especially into vulnerable areas, allows for a more comprehensive approach to IPC through better contextualisation of hand hygiene and PPE protocols, better identification of transmission risks, and the design and promotion of a wider range of preventive strategies and solutions.Funding source NHMRC APP100917