Invited review article: technology for attosecond science

We describe a complete technological system at Imperial College London for Attosecond Science studies. The system comprises a few-cycle, carrier envelope phase stabilized laser source which delivers sub 4 fs pulses to a vibration-isolated attosecond vacuum beamline. The beamline is used for the generation of isolated attosecond pulses in the extreme ultraviolet (XUV) at kilohertz repetition rates through laser-driven high harmonic generation in gas targets. The beamline incorporates: interferometers for producing pulse sequences for pump-probe studies; the facility to spectrally and spatially filter the harmonic radiation; an in-line spatially resolving XUV spectrometer; and a photoelectron spectroscopy chamber in which attosecond streaking is used to characterize the attosecond pulses. We discuss the technology and techniques behind the development of our complete system and summarize its performance. This versatile apparatus has enabled a number of new experimental investigations which we briefly describe.

Clinical experience with liraglutide

AIM

To provide insight into clinical experience with liraglutide by reviewing four case studies of patients initiating liraglutide treatment.

KEY FINDINGS

Liraglutide treatment was associated with clinically relevant reductions in glycated haemoglobin (HbA(1c.) ) levels. In two of three cases for which HbA(1c) information was available, patients achieved an HbA(1c) of 6.5% at 9-month follow-up and 6.1% at 12-month follow-up. In the third case, the HbA(1c) level was 7.5% at 18-month follow-up. Individuals treated with liraglutide also experienced clinically relevant weight reductions of 4-10%. Other non-glycaemic benefits of liraglutide treatment included reductions in blood pressure. There were no reported incidences of hypoglycaemia. Gastrointestinal adverse side effects were most commonly reported, including nausea, vomiting and dyspepsia; however, symptoms generally subsided during the first month of treatment. In one patient who had prolonged nausea with exenatide over 2 years, a treatment switch to liraglutide resulted in resolution of the nausea symptoms.

CONCLUSIONS

Liraglutide treatment was associated with reductions in HbA(1c) levels as well as benefits beyond glycaemic control, such as weight loss and systolic blood pressure reductions. No hypoglycaemic episode was reported. Transient gastrointestinal adverse side effects were most commonly reported.

Neighbourhood deprivation and physical activity in UK older adults

The benefits of regular physical activity for older adults are now well-established but this group remain the least active sector of the population. In this paper, the association between levels of neighbourhood deprivation and physical activity was assessed. A sample of 125 males with a mean age of 77.5 (±5.6) years, and 115 females with a mean age of age 78.6 (±8.6) underwent 7-day accelerometry, a physical performance battery, and completed a daily journeys log. Univariate associations between physical activity parameters and level of deprivation of neighbourhood were extinguished in regression models controlling for age, gender, and level of educational attainment. Age, gender, educational attainment, body mass index, physical function, and frequency of journeys from the home explained between 50% and 54% of variance in activity parameters. These results suggest the importance of strategies to help older adults maintain physical function, healthy weight, and remain active in their communities.

Mixed mould species in laboratory cultures of respiratory specimens: how should they be reported, and what are the indications for susceptibility testing?

AIMS

To investigate how clinical microbiology laboratories should report and interpret mixed mould isolates including Aspergillus species from clinical samples and the criteria for susceptibility testing of the isolates.

METHODS

Retrospectively collected data from our laboratory information system of moulds isolated between January 2005 and December 2007. Patient case notes were also reviewed.

RESULTS

A total of 502 isolates (from 273 patients) were found. 20 patients with clinical diagnosis of a probable fungal infection had mixed Aspergillus species.

CONCLUSIONS

In most instances, the isolation of Aspergillus species from non-sterile sites does not represent clinical disease, but only colonisation/contamination. However, for high-risk patients including transplant recipients, a positive culture is associated with invasive disease. Our tertiary centre routinely reports single fungal isolates and mixed cultures with appropriate comments, and those considered significant will also have susceptibility testing carried out. The correlation of culture results with clinical features can differentiate between invasive disease and contamination.

Dermatofibrosarcoma protuberans: 35 patients treated with Mohs micrographic surgery using paraffin sections

BACKGROUND

Dermatofibrosarcoma protuberans (DFSP) has conventionally been treated with wide local excision. More recently Mohs micrographic surgery (MMS) has been advocated.

OBJECTIVES

To assess our departmental experience with DFSP in the context of a literature review relating to DFSP treated with MMS.

METHODS

This was a case review of 35 patients with DFSP treated between 1998 and 2009 with MMS using paraffin-embedded sections.

RESULTS

Seventeen patients required one horizontal layer to clear their tumour, 10 patients needed two and eight patients needed three layers or more. The median preoperative clinical size was 6 cm(2) (range 0·75-54·8) and the median postoperative wound size was 46·8 cm(2) (range 4-145·2). Tumour persistence has not been observed in any of our patients after a median follow-up duration of 29·5 months (range 6-146).

CONCLUSIONS

We present 35 DFSP patients, none of whom showed persistent tumour after treatment with 'slow' MMS using paraffin sections. We advocate MMS as the treatment of choice for DFSP, especially for tumours over the head and neck region where tissue conservation is particularly important.

Processes associated with participation and adherence to a 12-month exercise programme for adults aged 70 and older

This study investigated the processes associated with the engagement of adults aged 70 years and older in a 12-month long research-based structured exercise programme. A sample of 21 participants (Mean age (SD) 75.8 (3.9); 14 females) and six exercise class leaders or researchers involved in the programme participated in individual semi-structured interviews. Transcripts were analysed with the principles of interpretive qualitative analysis. Our findings suggest that a programme that runs locally, provides individual attention/tailoring, delivers meaningful benefits, offers a staged approach to efficacy building, creates a sense of ownership, and provides intergenerational support and opportunities for social interaction, facilitates exercise engagement in later life.

Suppressed dissociation of H(2)(+) vibrational states by reduced dipole coupling

The suppression of H(2)(+) strong-field dissociation has intrigued experimentalists and theorists since the early days of laser-molecular science. We unravel a vibrational suppression effect due to weak dipole-matrix element coupling strengths of certain vibrational states, dependent on the laser frequency-a form of Cooper minima. This effect is demonstrated by our full-dimensional calculations on H(2)(+) dissociation and persists for a broad range of laser conditions including both weak and strong-field dissociation. Using a crossed-beams coincidence, three-dimensional momentum-imaging technique, the vibrational suppression effect is clearly observed for H(2)(+) and HD(+) at 790 and 395 nm, in good agreement with our theory.

Benchmark measurements of H(3)(+) nonlinear dynamics in intense ultrashort laser pulses

The H(3)(+) ion is the simplest polyatomic molecule and is destined to play a central role in understanding such molecules in intense ultrashort laser pulses. We present the first measurements of the intense field dissociation and ionization of D(3)(+) using coincidence three-dimensional momentum imaging. Our results show features that are a consequence of this molecule's unique equilateral triangular geometry, providing a fundamentally new system for theoretical development.

VX211, a vigorous new walnut hybrid clone with nematode tolerance and a useful resistance mechanism

VX211 is a highly vigorous Paradox hybrid clone that outgrew other walnut seedlings in the presence of nematodes. A four-year macroplot trial involving Paradox VX211 and a standard Paradox selection, AX1, demonstrated that the damage threshold level of Pratylenchus vulnus on commercially available walnut rootstocks is < 1 nematode/250 cm³ of soil. Using 1 as the initial population level (Pi) within an inoculation zone of 80 L of soil, the P. vulnus population level increased 2,500-fold in the first year of growth. Three years after inoculation soil population levels of P. vulnus on VX211 were significantly reduced compared to that of the moderately vigorous AX1. Growth of VX211 was 35% greater than that of AX1 regardless of the Pi. Examination of stained roots revealed that feeding and reproduction by P. vulnus on VX211 was primarily ectoparasitic. This is the first report on a new walnut rootstock that can be readily cloned, has high vigor, exhibits tolerance to low population levels of P. vulnus, reduces nematode feeding and reproduction within the root terminus, and is currently available to California growers.

Enhancing high-order above-threshold dissociation of H2+ beams with few-cycle laser pulses

High-order (three-photon or more) above-threshold dissociation (ATD) of H(2)(+) has generally not been observed using 800 nm light. We demonstrate a strong enhancement of its probability using intense 7 fs laser pulses interacting with beams of H(2)(+), HD(+), and D(2)(+) ions. The mechanism invokes a dynamic control of the dissociation pathway. These measurements are supported by theory that additionally reveals, for the first time, an unexpectedly large contribution to ATD from highly excited electronic states.

Excited ions in intense femtosecond laser pulses: laser-induced recombination

Electron-ion recombination in a laser-induced electron recollision is of fundamental importance as the underlying mechanism responsible for the generation of high-harmonic radiation and hence for the production of attosecond pulse trains in the extreme ultraviolet and soft x-ray spectral regions. By using an ion beam target, remotely prepared to be partially in long-lived excited states, the recombination process has for the first time been directly observed and studied.

New knowledge, new insights, and new recommendations

Scientific controversy and media hype in unexpected infant deaths