Effects of weak anchoring on C1 and C2 chevron structures

We present a theoretical study of the effect of weak anchoring on the transition between C1 and C2 chevron structures in smectic C liquid crystals. We employ a continuum theory which allows for variable cone, azimuthal and layer tilt angles. Equilibrium profiles for the director cone and azimuthal angles in the C1 and C2 states are calculated from the standard Euler-Lagrange minimisation of the total energy of the system. By comparing the total energies of the C1 and C2 states we can determine the globally stable chevron profile and calculate the critical temperature for the C1-C2 transition, which depends on anchoring strength and pretilt angle variations

Buckling of built-up columns of pultruded fiber-reinforced polymer C-sections

This paper presents the test results of an experimental investigation to evaluate the buckling behavior of built-up columns of pultruded profiles, subjected to axial compression. Specimens are assembled by using four (off the shelf) channel shaped profiles of E-glass fiber-reinforced polymer (FRP), having similar detailing to strut members in a large FRP structure that was executed in 2009 to start the restoration of the Santa Maria Paganica church in L’Aquila, Italy. This church had partially collapsed walls and no roof after the April 6, 2009, earthquake of 6.3 magnitude. A total of six columns are characterized with two different configurations for the bolted connections joining the channel sections into a built-up strut. Test results are discussed and a comparison is made with closed-form equation predictions for flexural buckling resistance, with buckling resistance values established from both eigenvalue and geometric nonlinear finite element analyses. Results show that there is a significant role played by the end loading condition, the composite action, and imperfections. Simple closed-form equations overestimate the flexural buckling strength, whereas the resistance provided by the nonlinear analysis provides a reasonably reliable numerical approach to establishing the actual buckling behavior

A safer place for patients: learning to improve patient safety

1 Every day over one million people are treated successfully by National Health Service (NHS) acute, ambulance and mental health trusts. However, healthcare relies on a range of complex interactions of people, skills, technologies and drugs, and sometimes things do go wrong. For most countries, patient safety is now the key issue in healthcare quality and risk management. The Department of Health (the Department) estimates that one in ten patients admitted to NHS hospitals will be unintentionally harmed, a rate similar to other developed countries. Around 50 per cent of these patient safety incidentsa could have been avoided, if only lessons from previous incidents had been learned. 2 There are numerous stakeholders with a role in keeping patients safe in the NHS, many of whom require trusts to report details of patient safety incidents and near misses to them (Figure 2). However, a number of previous National Audit Office reports have highlighted concerns that the NHS has limited information on the extent and impact of clinical and non-clinical incidents and trusts need to learn from these incidents and share good practice across the NHS more effectively (Appendix 1). 3 In 2000, the Chief Medical Officer’s report An organisation with a memory 1 , identified that the key barriers to reducing the number of patient safety incidents were an organisational culture that inhibited reporting and the lack of a cohesive national system for identifying and sharing lessons learnt. 4 In response, the Department published Building a safer NHS for patients3 detailing plans and a timetable for promoting patient safety. The goal was to encourage improvements in reporting and learning through the development of a new mandatory national reporting scheme for patient safety incidents and near misses. Central to the plan was establishing the National Patient Safety Agency to improve patient safety by reducing the risk of harm through error. The National Patient Safety Agency was expected to: collect and analyse information; assimilate other safety-related information from a variety of existing reporting systems; learn lessons and produce solutions. 5 We therefore examined whether the NHS has been successful in improving the patient safety culture, encouraging reporting and learning from patient safety incidents. Key parts of our approach were a census of 267 NHS acute, ambulance and mental health trusts in Autumn 2004, followed by a re-survey in August 2005 and an omnibus survey of patients (Appendix 2). We also reviewed practices in other industries (Appendix 3) and international healthcare systems (Appendix 4), and the National Patient Safety Agency’s progress in developing its National Reporting and Learning System (Appendix 5) and other related activities (Appendix 6). 6 An organisation with a memory1 was an important milestone in the NHS’s patient safety agenda and marked the drive to improve reporting and learning. At the local level the vast majority of trusts have developed a predominantly open and fair reporting culture but with pockets of blame and scope to improve their strategies for sharing good practice. Indeed in our re-survey we found that local performance had continued to improve with more trusts reporting having an open and fair reporting culture, more trusts with open reporting systems and improvements in perceptions of the levels of under-reporting. At the national level, progress on developing the national reporting system for learning has been slower than set out in the Department’s strategy of 2001 3 and there is a need to improve evaluation and sharing of lessons and solutions by all organisations with a stake in patient safety. There is also no clear system for monitoring that lessons are learned at the local level. Specifically: a The safety culture within trusts is improving, driven largely by the Department’s clinical governance initiative 4 and the development of more effective risk management systems in response to incentives under initiatives such as the NHS Litigation Authority’s Clinical Negligence Scheme for Trusts (Appendix 7). However, trusts are still predominantly reactive in their response to patient safety issues and parts of some organisations still operate a blame culture. b All trusts have established effective reporting systems at the local level, although under-reporting remains a problem within some groups of staff, types of incidents and near misses. The National Patient Safety Agency did not develop and roll out the National Reporting and Learning System by December 2002 as originally envisaged. All trusts were linked to the system by 31 December 2004. By August 2005, at least 35 trusts still had not submitted any data to the National Reporting and Learning System. c Most trusts pointed to specific improvements derived from lessons learnt from their local incident reporting systems, but these are still not widely promulgated, either within or between trusts. The National Patient Safety Agency has provided only limited feedback to trusts of evidence-based solutions or actions derived from the national reporting system. It published its first feedback report from the Patient Safety Observatory in July 2005

Multistable alignment states in nematic liquid crystal filled wells

Two distinct, stable alignment states have been observed for a nematic liquid crystal confined in a layer with thickness of 12 μm and in square wells with sides of length between 20 and 80 μm. The director lies in the plane of the layer and line defects occur in two corners of the squares. The positions of the defects determine whether the director orientation is across the diagonal or is parallel to two opposite edges of the square. The device is multistable because both the diagonal and parallel states are stable when rotated by multiples of 90° in plane

Response of beam-to-column web cleated joints for FRP pultruded members

Physical testing is used to characterize the structural properties of beam-to-column joints, comprising pultruded fiber-reinforced polymer (FRP) H-shapes of depth 203 mm, connected by 128 mm-long web cleats and two M16 bolts per leg. Testing is performed on two batches of nominally identical specimens. One batch had web cleats of pultruded FRP and the other had structural steel. The structural behavior of the joints is based on their moment-rotation responses, failure modes, and serviceability vertical deflection limits. Joints with FRP cleats failed by delamination cracking at the top of the cleats, and when the cleats were of steel, the FRP failure occurred inside the column members. Neither failure mode is reported in the design manuals from pultruders. At the onset of the FRP damage, it was found that the steel joints were twice as stiff as the FRP joints. On the basis of a characteristic (damage) rotation, calculated in accordance with Eurocode 0, the serviceability deflection limits are established to be span/300 and span/650 for the joints with FRP and steel cleats, respectively. This finding suggests that appropriate deflection limits, in relation to cleated connections, should be proposed in manufactures’ design manuals and relative design standards and design codes. Failure to address the serviceability, by the engineer of record, could lead to unreliable designs

Classifying the embedded young stellar population in Perseus and Taurus & the LOMASS database

Context. The classification of young stellar objects (YSOs) is typically done using the infrared spectral slope or bolometric temperature, but either can result in contamination of samples. More accurate methods to determine the evolutionary stage of YSOs will improve the reliability of statistics for the embedded YSO population and provide more robust stage lifetimes. Aims. We aim to separate the truly embedded YSOs from more evolved sources. Methods. Maps of HCO+ J=4-3 and C18O J=3-2 were observed with HARP on the James Clerk Maxwell Telescope (JCMT) for a sample of 56 candidate YSOs in Perseus and Taurus in order to characterize emission from high (column) density gas. These are supplemented with archival dust continuum maps observed with SCUBA on the JCMT and Herschel PACS to compare the morphology of the gas and dust in the protostellar envelopes. The spatial concentration of HCO+ J=4-3 and 850 micron dust emission are used to classify the embedded nature of YSOs. Results. Approximately 30% of Class 0+I sources in Perseus and Taurus are not Stage I, but are likely to be more evolved Stage II pre-main sequence (PMS) stars with disks. An additional 16% are confused sources with an uncertain evolutionary stage. Conclusions. Separating classifications by cloud reveals that a high percentage of the Class 0+I sources in the Perseus star forming region are truly embedded Stage I sources (71%), while the Taurus cloud hosts a majority of evolved PMS stars with disks (68%). The concentration factor method is useful to correct misidentified embedded YSOs, yielding higher accuracy for YSO population statistics and Stage timescales. Current estimates (0.54 Myr) may overpredict the Stage I lifetime on the order of 30%, resulting in timescales of 0.38 Myr for the embedded phase.Comment: 33 pages, 21 figures, 6 tables, Accepted to be published in A&

Analytic solutions of a simple advection-diffusion model of an oxygen transfer device

Artificial blood oxygenation is an essential aspect of cardiopulmonary bypass surgery, maintaining physiological levels of oxygen and carbon dioxide in the blood, and thus temporarily replacing the normal function of the lungs. The blood-gas exchange devices used for such procedures have a long history and have had varying degrees of success. In this paper we consider a simple model of a new approach to enhancing the diffusion of oxygen into the blood while it is contained in the artificial blood oxygenator. We show that using a transverse flow, which may be set up using mixing elements that we have previously shown experimentally to enhance blood oxygenation, will increase the oxygen levels within the blood. This simple model and associated analytic solutions can then be used to aid the optimisation of blood oxygenation devices

RISE: a fast-readout imager for exoplanet transit timing

By the precise timing of the low amplitude (0.005 - 0.02 magnitude) transits of exoplanets around their parent star it should be possible to infer the presence of other planetary bodies in the system down to Earth-like masses. We describe the design and construction of RISE, a fast-readout frame transfer camera for the Liverpool Telescope designed to carry out this experiment. The results of our commissioning tests are described as well as the data reduction procedure necessary. We present light curves of two objects, showing that the desired timing and photometric accuracy can be obtained providing that autoguiding is used to keep the target on the same detector pixel for the entire (typically 4 hour) observing run.Comment: Published in PROC SPIE, vol 7014, 70416

Interferometric method for determining the sum of the flexoelectric coefficients (e1+e3) in an ionic nematic material

The time-dependent periodic distortion profile in a nematic liquid crystal phase grating has been measured from the displacement of tilt fringes in a Mach-Zehnder interferometer. A 0.2 Hz squarewave voltage was applied to alternate stripe electrodes in an interdigitated electrode geometry. The time-dependent distortion profile is asymmetric with respect to the polarity of the applied voltage and decays with time during each half period due to ionic shielding. This asymmetry in the response allows the determination of the sum of the flexoelectric coefficients (e1+e3) using nematic continuum theory since the device geometry does not possess inherent asymmetry