Co-percolation to tune conductive behaviour in dynamical metallic nanowire networks.

Nanowire networks act as self-healing smart materials, whose sheet resistance can be tuned via an externally applied voltage stimulus. This memristive response occurs due to modification of junction resistances to form a connectivity path across the lowest barrier junctions in the network. While most network studies have been performed on expensive noble metal nanowires like silver, networks of inexpensive nickel nanowires with a nickel oxide coating can also demonstrate resistive switching, a common feature of metal oxides with filamentary conduction. However, networks made from solely nickel nanowires have high operation voltages which prohibit large-scale material applications. Here we show, using both experiment and simulation, that a heterogeneous network of nickel and silver nanowires allows optimization of the activation voltage, as well as tuning of the conduction behavior to be either resistive switching, memristive, or a combination of both. Small percentages of silver nanowires, below the percolation threshold, induce these changes in electrical behaviour, even for low area coverage and hence very transparent films. Silver nanowires act as current concentrators, amplifying conductivity locally as shown in our computational dynamical activation framework for networks of junctions. These results demonstrate that a heterogeneous nanowire network can act as a cost-effective adaptive material with minimal use of noble metal nanowires, without losing memristive behaviour that is essential for smart sensing and neuromorphic applications.

Programmability of nanowire networks.

Electrical connectivity in networks of nanoscale junctions must be better understood if nanowire devices are to be scaled up from single wires to functional material systems. We show that the natural connectivity behaviour found in random nanowire networks presents a new paradigm for creating multi-functional, programmable materials. In devices made from networks of Ni/NiO core-shell nanowires at different length scales, we discover the emergence of distinct behavioural regimes when networks are electrically stressed. We show that a small network, with few nanowire-nanowire junctions, acts as a unipolar resistive switch, demonstrating very high ON/OFF current ratios (>10(5)). However, large networks of nanowires distribute an applied bias across a large number of junctions, and thus respond not by switching but instead by evolving connectivity. We demonstrate that these emergent properties lead to fault-tolerant materials whose resistance may be tuned, and which are capable of adaptively reconfiguring under stress. By combining these two behavioural regimes, we demonstrate that the same nanowire network may be programmed to act both as a metallic interconnect, and a resistive switch device with high ON/OFF ratio. These results enable the fabrication of programmable, multi-functional materials from random nanowire networks.

Implementing Surviving Sepsis guidelines in a district general hospital.

We describe efforts made at Blackpool Victoria Hospital to implement the well-established international Surviving Sepsis guidelines. These included posters, pocket guides and stickers inserted in patient notes. All doctors and nurses in acute areas received specific information and education. Sepsis teams comprising both doctors and nurses were formed to encourage implementation and to audit and disseminate data. Data collection occurred from February to November 2009. Cases were considered prospectively at the time of initial assessment and 198 patients were identified; 169 (85%) had blood cultures taken; 146 (74%) had lactate levels measured; and 145 (74%) received antibiotics within the target time. We believe these results demonstrate relatively effective implementation of guidelines in the challenging environment of a district general hospital. Our results could be replicated easily and provide a good way of reducing patient mortality at minimal financial cost.

Prehospital deaths in the Yorkshire Health Region.

OBJECTIVES: To estimate the proportion of prehospital deaths in a British population of trauma victims which may be preventable, and to investigate the effect of death at the scene and death in transit on potential survivorship. METHODS: Blinded review, by four specialists with an interest in trauma, of necropsy results and details of age, sex, and mechanism of injury for prehospital trauma deaths in the Yorkshire Health Region in a 12 month period. RESULTS: Complete records were traced on 305 of 337 trauma deaths, 190 being recorded as dead on arrival of emergency services and 115 dead on arrival at hospital. In the group declared dead at the scene, three of the four assessors considered 93% of deaths to have been inevitable and only 2% as potential survivors (25% of this group sustaining inevitably fatal injuries such as brain avulsion or decapitation). In the group dead on arrival 81% were felt to be inevitable deaths and 5% potential survivors. CONCLUSIONS: There seems to be less scope for salvage of victims of trauma death in a British population than has been recorded in America, possibly due to a higher proportion of blunt trauma deaths here. Those who die in transit consist of a less severely injured group with a higher potential for survival.

Haemodynamic effects of propofol: induction with 2.5 mg kg-1.

Serial measurements of haemodynamic variables were performed at 1-min intervals in nine ASA I, unpremedicated patients before and for 5 min after induction of anaesthesia with propofol 2.5 mg kg-1. End-tidal carbon dioxide concentration was maintained within the normal range. Stroke volume and left ventricular function were measured by Doppler and cross-sectional echocardiography at the aortic valve. Systemic arterial pressure was measured by automated oscillotonometry and heart rate by electrocardiograph. Stroke volume, cardiac output, systemic vascular resistance, left ventricular stroke work and rate-pressure product were calculated. There was a decrease at all time points in systolic, mean and diastolic arterial pressure. There was an initial increase in heart rate and cardiac output, with a subsequent decrease to less than baseline. There was an initial decrease in systemic vascular resistance followed by partial recovery, and a delayed decrease in left ventricular function as measured by peak aortic blood flow velocity and acceleration.

Induction and recovery characteristics of desflurane in day case patients: a comparison with propofol.

Desflurane is an ether halogenated exclusively with fluorine. It has a blood/gas partition coefficient of 0.42 (cf. isoflurane 1.40 and nitrous oxide 0.46). This characteristic suggests that it should provide both a fast induction of anaesthesia and a rapid recovery from anaesthesia. To assess this, 60 patients were entered into a study and allocated at random to one of four groups receiving either desflurane or propofol for induction and maintenance of anaesthesia. Desflurane caused loss of consciousness in approximately 2 minutes during gaseous inductions. The psychomotor scores in the patients who received propofol for induction and maintenance of anaesthesia were significantly worse compared with those who were given desflurane for either induction and maintenance or for maintenance only. There was also a tendency for other recovery parameters to be faster in the patients receiving desflurane although this did not reach statistical significance. This suggests that desflurane would be a suitable agent for day case anaesthesia providing for a rapid recovery.

Oxygen delivery systems--a comparison of two devices.

Two low-volume, variable performance oxygen delivery systems were compared in conscious spontaneously breathing volunteers. Oropharyngeal oxygen concentrations were measured during periods of nose and mouth breathing. The systems were studied at oxygen flow rates of 2 or 4 litres/minute. The performance of both systems was similar under the test conditions but the nasal catheter is preferable in terms of cost.

Insulin protects cognitive function in experimental stroke.

There is evidence from in vitro systems that the extent of neuronal loss in acute central nervous system ischaemia can be reduced by manoeuvres which restrict availability of glucose to the ischaemic area. Experiments were designed to test whether hypoglycaemia induced with insulin is associated with improved behavioural outcome in a recovery model of stroke. Rats learned a maze task as a test of working memory, believed to be subserved by the hippocampus, and then had a period of cerebral ischaemia, followed by reperfusion. After an interval of 14 days they were tested on the same maze, where lesioned animals had very significant (p less than 0.0001) impairment of working memory, whereas lesioned and treated (2.0 u/kg-1 insulin, minimum single plasma glucose value: 3.1 mmol/l-1) animals were indistinguishable from control animals. It is concluded that a striking degree of protection can be obtained with levels of mild hypoglycaemia which may be acceptable and practicable for use in humans.

Hyposensitization to poison ivy after working in a cashew nut shell oil processing factory.

19 adults were patch tested to urushiol, the allergen in poison ivy/oak, to determine their sensitivity to this allergen after working in a cashew nut shell oil (CNSO) processing plant. The cashew nut tree and poison ivy/oak are in the same botanical family. Anacardiaceae, and they share similar chemicals which cause allergic contact dermatitis. 13 of the 19 workers had a preemployment history of poison ivy sensitivity, with 10 developing CNSO dermatitis. After working in this factory for several months, 9 of the 13 noticed a decreased sensitivity or no sensitivity to poison ivy/oak. When tested to urushiol extract, only 3 reacted positively, 2 minimally. These results imply that hyposensitization to poison ivy/oak occurred in these employees after development of hardening to cashew nut shell oil.

Detection of IgG subclass-specific anti-IgE antibodies in normal and atopic individuals.

Atopic dermatitis and atopic asthma patients were shown to have elevated IgG anti-IgE levels compared with those of controls. When the pattern of IgG subclass anti-IgE activity was studied, further differences between the three groups became apparent. Adults with atopic dermatitis had elevated IgG1 and IgG4 anti-IgE compared with those of controls but no corresponding increase in the IgG2 or IgG3 subclasses. For Sri Lankan children with atopic asthma and a high incidence of Nematoda infection, elevated anti-IgE was restricted to the IgG1 subclass. While IgG1 anti-IgE proved to be the predominant subclass for both atopic groups, IgG2 anti-IgE was the major subclass among controls.

Segmenting dot patterns by voronoi diagram concavity.

This correspondence defines a signed distance, called ``internal concavity,'' on paths of the Voronoi diagram of a dot pattern. An algorithm using internal concavity to segment dot patterns is described. The segmentation algorithm produces subsets of the Dirichlet tessellation (Delaunay triangulation) of the dot pattern.

Uncouplers and the molecular mechanism of uncoupling in mitochondria.

Uncouplers are molecules with protonophoric and ionophoric capabilities that mediate coupled cyclical transport of cations--a transport that takes precedence over all other coupled processes. Uncouplers form cation-containing complexes with electrogenic ionophores that potentiate cyclical transport of cations. The molecular mechanism of uncoupling sheds strong light on the mechanism of coupling.

A new method for the isolation of methionyl transfer RNA synthetase mutants from Escherichia coli.

Six methionine auxotrophs were isolated from an E. coli K-12 strain which required up to 100 times as much methionine for growth as a conventional auxotroph. In these mutants the methionyl-tRNA synthetase had an increased Km for methionine. The Km value for the mutants ranged from 0.48 to 1.63 mM, compared to 0.078 mM for the wild type. The Km (methionine) for S-adenosyl methionine synthetase was not altered.