Hydrogen in Ti and Zr alloys: industrial perspective, failure modes and mechanistic understanding.

Titanium is widely used in demanding applications, such as in aerospace. Its strength-to-weight ratio and corrosion resistance make it well suited to highly stressed rotating components. Zirconium has a no less critical application where its low neutron capture cross section and good corrosion resistance in hot water and steam make it well suited to reactor core use, including fuel cladding and structures. The similar metallurgical behaviour of these alloy systems makes it alluring to compare and contrast their behaviour. This is rarely undertaken, mostly because the industrial and academic communities studying these alloys have little overlap. The similarities with respect to hydrogen are remarkable, albeit potentially unsurprising, and so this paper aims to provide an overview of the role hydrogen has to play through the material life cycle. This includes the relationship between alloy design and manufacturing process windows, the role of hydrogen in degradation and failure mechanisms and some of the underpinning metallurgy. The potential role of some advanced experimental and modelling techniques will also be explored to give a tentative view of potential for advances in this field in the next decade or so.This article is part of the themed issue 'The challenges of hydrogen and metals'.

Systematic review with meta-analysis: placebo rates in induction and maintenance trials of Crohn's disease.

BACKGROUND: Minimising placebo response is essential for drug development. AIM: To conduct a meta-analysis to determine placebo response and remission rates in trials and identify the factors affecting these rates. METHODS: MEDLINE, EMBASE and CENTRAL were searched from inception to April 2014 for placebo-controlled trials of pharmacological interventions for Crohn's disease. Placebo response and remission rates for induction and maintenance trials were pooled by random-effects and mixed-effects meta-regression models to evaluate effects of study-level characteristics on these rates. RESULTS: In 100 studies containing 67 induction and 40 maintenance phases and 7638 participants, pooled placebo remission and response rates for induction trials were 18% [95% confidence interval (CI) 16-21%] and 28% (95% CI 24-32%), respectively. Corresponding values for maintenance trials were 32% (95% CI 25-39%) and 26% (95% CI 19-35%), respectively. For remission, trials enrolling patients with more severe disease activity, longer disease duration and more study centres were associated with lower placebo rates, whereas more study visits and longer study duration was associated with higher placebo rates. For response, findings were opposite such that trials enrolling patients with less severe disease activity and longer study duration were associated with lower placebo rates. Placebo rates varied by drug class and route of administration, with the highest placebo response rates observed for biologics. CONCLUSIONS: Placebo rates vary according to whether trials are designed for induction or maintenance and the factors influencing them differ for the endpoints of remission and response. These findings have important implications for clinical trial design in Crohn's disease.

A model of antennal wall-following and escape in the cockroach.

Cockroaches exploit tactile cues from their antennae to avoid predators. During escape running the same sensors are used to follow walls. We hypothesise that selection of these mutually exclusive behaviours can be explained without representation of the stimulus or an explicit switching mechanism. A neural model is presented that embodies this hypothesis. The model incorporates behavioural and neurophysiological data and is embedded in a mobile robot in order to test the response to stimuli in the real world. The system is shown to account for data on escape direction and high-speed wall-following in the cockroach, including the counter-intuitive observation that faster running cockroaches maintain a closer distance to the wall. The wall-following behaviour is extended to include discrimination of tactile escape cues according to behavioural context. We conclude by highlighting questions arising from the robot experiments that suggest interesting hypotheses to test in the cockroach.

Nitrogen embolus as a complication of hepatic cryosurgery.

A case of near-fatal nitrogen embolism during hepatic cryosurgery is presented. Modifications of liquid nitrogen probes, which prevent direct contact of liquid nitrogen with the tissue being frozen, can prevent this type of injury.

Identification of factors responsible for wound infection following allograft nephrectomy.

The advisability of routine allograft nephrectomy following rejection has not been clearly resolved. Rejected transplants may be a source of sepsis, local inflammatory symptoms, and continued antigenic stimulation. Transplant nephrectomy is, however, attended by a surprisingly high incidence of septic complications and death. In an attempt to analyze the occurrence of these, and identify effective prophylactic maneuvers, the authors retrospectively studied 99 consecutive allograft nephrectomies in 252 consecutive renal transplants. Mortality following allograft nephrectomy was 10 per cent, and usually attributable to sepsis. Wound infections occurred in 24 per cent of these patients and were significantly associated with a preoperative site of infection in the wound, urinary tract, or blood (P less than 0.01). Preoperative antibiotics, wound irrigation, drains, and delay in performing allograft nephrectomy were all found to be insignificant variables. Interestingly, total steroid dose was less in patients who developed wound infections than in those who did not (P less than 0.01). A postoperative wound infection approximately doubled the mean number of hospital days. These data suggest that a significant reduction in morbidity and possibly mortality could be accomplished by complete eradication of infection prior to allograft nephrectomy. Consequent delay in removal of the graft is not associated with increased morbidity, and other maneuvers seem to have little beneficial effect.