Corrosion of silicon carbide ceramics using conventional and electrochemical methods

Silicon carbide ceramics are candidate materials for use in aggressive environments, including those where aqueous acids are present. Standard corrosion testing methods such as immersion testing are not always sufficiently sensitive for these ceramics owing to the very low, almost unobservable, corrosion rates encountered. Using electrochemical methods the corrosion processes can be assisted, leading to higher rates and thus the elucidation of reaction mechanisms. The behaviour of a sintered and a reaction bonded silicon carbide has been investigated in aqueous HCl, HF, HNO3, and H2SO4, using standard immersion and new electrochemical methods. Both materials were passive in HCl, HNO3, and H2SO4 because of the formation of a surface silica film, and were active in HF. In HF, corrosion of sintered silicon carbide was slight and the residual silicon was removed from reaction bonded specimens.

Optical quality for keratoconic eyes with conventional RGP lens and simulated, customised contact lens corrections:a comparison

Purpose: To compare monochromatic aberrations of keratoconic eyes when uncorrected, corrected with spherically-powered RGP (rigid gas-permeable) contact lenses and corrected using simulations of customised soft contact lenses for different magnitudes of rotation (up to 15°) and translation (up to 1mm) from their ideal position. Methods: The ocular aberrations of examples of mild, moderate and severe keratoconic eyes were measured when uncorrected and when wearing their habitual RGP lenses. Residual aberrations and point-spread functions of each eye were simulated using an ideal, customised soft contact lens (designed to neutralise higher-order aberrations, HOA) were calculated as a function of the angle of rotation of the lens from its ideal orientation, and its horizontal and vertical translation. Results: In agreement with the results of other authors, the RGP lenses markedly reduced both lower-order aberrations and HOA for all three patients. When compared with the RGP lens corrections, the customised lens simulations only provided optical improvements if their movements were constrained within limits which appear to be difficult to achieve with current technologies. Conclusions: At the present time, customised contact lens corrections appear likely to offer, at best, only minor optical improvements over RGP lenses for patients with keratoconus. If made in soft materials, however, these lenses may be preferred by patients in term of comfort. © 2012 The College of Optometrists.

Comparison between conventional and stochastic pinning control

Theoretical developments on pinning control of complex dynamical networks have mainly focused on the deterministic versions of the model dynamics. However, the dynamical behavior of most real networks is often affected by stochastic noise components. In this paper the pinning control of a stochastic version of the coupled map lattice network with spatiotemporal characteristics is studied. The control of these complex dynamical networks have functional uncertainty which should be considered when calculating stabilizing control signals. Two feedback control methods are considered: the conventional feedback control and modified stochastic feedback control. It is shown that the typically-used conventional control method suffers from the ignorance of model uncertainty leading to a reduction and potentially a collapse in the control efficiency. Numerical verification of the main result is provided for a chaotic coupled map lattice network. © 2011 IEEE.

Free radical reaction products and antioxidant capacity in beating heart coronary artery surgery compared to conventional bypass

Oxygen-derived free radicals are important agents of tissue injury during ischemia and reperfusion. The aim of this study was to investigate changes in protein and lipid oxidation and antioxidant status in beating heart coronary artery surgery and conventional bypass and to compare oxidative stress parameters between the two bypass methods. Serum lipid hydroperoxide, nitric oxide, protein carbonyl, nitrotyrosine, vitamin E, and β-carotene levels and total antioxidant capacity were measured in blood of 30 patients undergoing beating heart coronary artery surgery (OPCAB, off-pump coronary artery bypass grafting) and 12 patients undergoing conventional bypass (CABG, on-pump coronary artery bypass grafting). In the OPCAB group, nitric oxide and nitrotyrosine levels decreased after reperfusion. Similarly, β-carotene level and total antioxidant capacity also decreased after anesthesia and reperfusion. In the CABG group, nitric oxide and nitrotyrosine levels decreased after ischemia and reperfusion. However, protein carbonyl levels elevated after ischemia and reperfusion. Vitamin E, β-carotene, and total antioxidant capacity decreased after ischemia and reperfusion. Significantly decreased nitration and impaired antioxidant status were seen after reperfusion in both groups. Moreover, elevated protein carbonyls were found in the CABG group. The off-pump procedure is associated with lower degree of oxidative stress than on-pump coronary surgery. © 2011 Pleiades Publishing, Ltd.

Role of community pharmacists in the use of antipsychotics for behavioural and psychological symptoms of dementia (BPSD):a qualitative study

OBJECTIVE: This study aimed to use qualitative methodology to understand the current role of community pharmacists in limiting the use of antipsychotics prescribed inappropriately for behavioural and psychological symptoms of dementia. DESIGN: A qualitative study employing focus groups was conducted. Data were analysed using thematic analysis. SETTING: 3 different geographical locations in the England. PARTICIPANTS: Community pharmacists (n=22). RESULTS: The focus groups identified an array of factors and constraints, which affect the ability of community pharmacists to contribute to initiatives to limit the use of antipsychotics. 3 key themes were revealed: (1) politics and the medical hierarchy, which created communication barriers; (2) how resources and remit impact the effectiveness of community pharmacy; and (3) understanding the nature of the treatment of dementia. CONCLUSIONS: Our findings suggest that an improvement in communication between community pharmacists and healthcare professionals, especially general practitioners (GPs) must occur in order for community pharmacists to assist in limiting the use of antipsychotics in people with dementia. Additionally, extra training in working with people with dementia is required. Thus, an intervention which involves appropriately trained pharmacists working in collaboration with GPs and other caregivers is required. Overall, within the current environment, community pharmacists question the extent to which they can contribute in helping to reduce the prescription of antipsychotics.

On the stability of conventional and nano-structured carbon-based catalysts in the oxidative dehydrogenation of ethylbenzene under industrially relevant conditions

Relevant carbon-based materials, home-made carbon-silica hybrids, commercial activated carbon, and nanostructured multi-walled carbon nanotubes (MWCNT) were tested in the oxidative dehydrogenation of ethylbenzene (EB). Special attention was given to the reaction conditions, using a relatively concentrated EB feed (10 vol.% EB), and limited excess of O2 (O 2:EB = 0.6) in order to work at full oxygen conversion and consequently avoid O2 in the downstream processing and recycle streams. The temperature was varied between 425 and 475 °C, that is about 150-200 °C lower than that of the commercial steam dehydrogenation process. The stability was evaluated from runs of 60 h time on stream. Under the applied reactions conditions, all the carbon-based materials are apparently stable in the first 15 h time on stream. The effect of the gasification/burning was significantly visible only after this period where most of them fully decomposes. The carbon of the hybrids decomposes completely rendering the silica matrix and the activated carbon bed is fully consumed. Nano structured MWCNT is the most stable; the structure resists the demanding reaction conditions showing an EB conversion of ∼30% (but deactivating) with a steady selectivity of ∼80%. The catalyst stability under the ODH reaction conditions is predicted from the combustion apparent activation energies. © 2014 Elsevier Ltd. All rights reserved.

Mental health pharmacists views on shared decision-making for antipsychotics in serious mental illness

Background People diagnosed with serious mental illnesses (SMIs) such as schizophrenia and bipolar affective disorder are frequently treated with antipsychotics. National guidance advises the use of shared decision-making (SDM) in antipsychotic prescribing. There is currently little data on the opinions of health professionals on the role of SDM. Objective To explore the views and experiences of UK mental health pharmacists regarding the use of SDM in antipsychotic prescribing in people diagnosed with SMI. Setting The study was conducted by interviewing secondary care mental health pharmacists in the UK to obtain qualitative data. Methods Semi-structured interviews were recorded. An inductive thematic analysis was conducted using the method of constant comparison. Main outcome measure Themes evolving from mental health pharmacists on SDM in relation to antipsychotic prescribing in people with SMI. Results Thirteen mental health pharmacists were interviewed. SDM was perceived to be linked to positive clinical outcomes including adherence, service user satisfaction and improved therapeutic relations. Despite more prescribers and service users supporting SDM, it was not seen as being practised as widely as it could be; this was attributed to a number of barriers, most predominantly issues surrounding service user’s lacking capacity to engage in SDM and time pressures on clinical staff. The need for greater effort to work around the issues, engage service users and adopt a more inter-professional approach was conveyed. Conclusion The mental health pharmacists support SDM for antipsychotic prescribing, believing that it improves outcomes. However, barriers are seen to limit implementation. More research is needed into overcoming the barriers and measuring the benefits of SDM, along with exploring a more inter-professional approach to SDM.