Experimental and simulation characterisation of flexural vibration modes in unimorph ultrasound transducers.

A unimorph flexural transducer design is proposed and tested with regard to mode shapes and frequencies. The transducers consist of a passive metal cap structure, and a thin piezoelectric disc, rigidly bonded to the inside. Extensive finite element (FE) modelling, and experimental 2D, time-resolved displacement measurements were done to characterise the transducers flexural properties, and to compare them to the analytical solutions of thin vibrating plates. Emphasis was put on characterising the passive layer of the unimorph structure, before bonding the piezoelectric element, to understand how the active element affects the behaviour of the flexing plate. A high power Nd:YAG laser was used to actuate the metal plate (non-contact), and the frequency content of the resulting displacement signal was analysed to identify the flexural modes. The non-axisymmetric modes, which are conventionally disregarded because of their unfavourable acoustic properties, were also taken into account. There was excellent agreement between the experimental results and the FE simulation data. There was good agreement with the analytical edge clamped plate model, but with some notable deviations, which have not previously been identified or commented upon. Specifically, the second axisymmetric mode is split into three separate modes, which is not explained by the traditional theory of vibrating plates.

A randomized controlled trial of postoperative analgesia following total knee replacement: transdermal Fentanyl patches versus patient controlled analgesia (PCA).

BACKGROUND: This randomized controlled trial compared a standard patient controlled analgesic (PCA) regime with a transdermal and oral Fentanyl regime for post-operative pain management in patients undergoing total knee replacement. METHODS: One hundred and ninety-six patients undergoing total knee replacement were recruited. Pre- and post-operatively Visual Analogue Score (VAS), Oxford Knee Score, Health Anxiety and Depression Score and Brief Pain Inventory Score were completed. According to the day 1, VAS score patients were randomly allocated to either a PCA regime or a Fentanyl transdermal/oral regime. Patient reported outcomes were measured until the patients were discharged. RESULTS: The results demonstrate that in terms of analgesic effect, day of discharge and side effect profile the two regimes are comparable. CONCLUSIONS: We conclude that a Fentanyl transdermal regime provides adequate analgesic effect comparable to a standard PCA regime in conjunction with a low side effect profile. Using a transdermal analgesic system provides efficient continuous delivery enabling a smooth transition from hospital to home within the first week. Transdermal Fentanyl provides an alternative analgesic regime that can provide an equivalent analgesic effect so as to enable a satisfactory outcome for the patient in terms of function and pain. LEVEL OF EVIDENCE: II.

Ergonomics action research I: shifting from hypothesis testing to experiential learning.

This paper presents the case for the need for 'Action Research' (AR) approaches to gain understanding of how ergonomics considerations can best be integrated into the design of new work systems. The AR researchers work collaboratively with other stakeholders to solve a real-world problem: gaining insight into the problem and factors influencing solution building from an embedded position in the development process. This experience is interpreted in terms of available theory and can support further theory development. This non-experimental approach can help provide practical new approaches for integrating ergonomics considerations into real work system design processes. The AR approach suffers from a lack of acceptance by conventionally trained scientists. This paper aims to help overcome this weakness by developing the underlying theory and rationale for using AR approaches in ergonomics research. We propose further development of hybrid approaches which incorporate other evaluation techniques to extend the knowledge gains from AR projects. PRACTITIONER SUMMARY: Researchers should engage directly with organisations in ergonomics projects so that they can better understand the challenges and needs of practitioners who are trying to apply available scientific knowledge in their own unique context. Such 'Action Research' could help develop theory and approaches useful to improve mobilisation and application of ergonomics knowledge in organisations.

Audit-induced change reduces complications of the Ganz trochanteric flip approach.

INTRODUCTION: The Ganz trochanteric flip approach aims to avoid the potential risk of avascular necrosis in hip conserving surgery and may reduce the risk of femoral neck fractures, neck thinning and femoral head implant migration in hip resurfacing. Our initial audit revealed the complications of non-union and trochanteric screw irritation to be associated with this approach. We, therefore, modified our selection criteria and re-audited our results. SUBJECTS AND METHODS: The initial audit (IA) ran between January 2003 and November 2007 after which an age limit of 50 years was recommended. The re-audit (RA) ran between November 2007 and December 2008 where one of the senior authors stopped using the approach in the over 50 year age group whilst the other senior author continued on selected patients over 50 years. RESULTS: There were 545 hips in the IA and 152 hips in the RA group. The incidence of non-union decreased in the RA after the change of selection criteria (6.2% [IA] vs 1.3% [RA]). In both audit groups, the incidence of non-union increased with age, and in the RA no non-unions were observed under the age of 50 years. The incidence of screw irritation and the necessity for removal remained relatively unchanged (20.7% [IA] vs 28.3% [RA]) with a combined incidence of 22.4%. CONCLUSIONS: The trochanteric flip approach to the hip can be used safely with an acceptable complication rate in young adult impingement and resurfacing surgery. Caution must, however, be exercised in patients over 50 years of age as they have a higher incidence of trochanteric non-union. In addition, all patients should be consented for the possibility of screw removal as a second procedure.

Effects of size on predation risk, behavioural response to fish, and cost of reduced feeding in larval Ischnura verticalis (Coenagrionidae: Odonata).

We used laboratory studies to examine the role of predation risk and cost of anti-predator behaviour in determining the behavioural response of several larval instars of Ischnura verticalis to a fish predator (Lepomis gibbosus). Smaller larvae were less susceptible to fish predation than larger larvae. Smaller larvae depressed movement to a greater degree in the presence of fish than did larger larvae; large larvae were generally less active than small larvae regardless of fish presence. Reduced feeding resulted in smaller larvae suffering more in terms of reduced growth than did large larvae. In general, our results tend to support the hypothesis that individuals that suffer high costs of anti-predator behaviour but little risk of predation may only exhibit anti-predator behaviours in the presence of predators, whereas individuals with a higher risk of predation and a lower cost of anti-predator behaviour may evolve anti-predator mechanisms that are in effect even in the absence of predators.

Acute renal dysfunction after major arteriography.

The incidence of acute renal dysfunction (ARD) after major arteriography was evaluated by assessment of the change in serum creatinine in 364 patients undergoing arteriography. Major arteriography was defined as abdominal aortography, abdominal aortography with lower-extremity runoff, aortic arch studies, or aortic arch plus selective carotid angiography. The influence of the volume of contrast material received, hydration, and associated risk factors was evaluated. In the entire group, the frequency of postarteriographic ARD was 7.1%. Although most patients recovered, 1.4% required renal dialysis. The frequency of renal dysfunction was significantly higher in patients with preexisting renal disease (14.8%), and 3.7% of these patients went on to require dialysis. In the total group and in those with normal renal function prearteriographically, the frequency of ARD was found to be related to the volume of iodinated contrast material received. Hydration before, during, and after angiography did not prevent this complication. Several risk factors, namely preexisting renal disease, advanced age, volume of contrast material used, type of study performed, diabetes mellitus, and coexistent heart disease were found to be associated with a statistically significant increased risk of postangiographic ARD.

Risk of renal failure after major angiography.

In 400 patients who underwent major aortography, acute renal dysfunction (ARD) occurred in 11.3%. Of the group with normal renal function before the procedure, 8.2% had ARD and 0.8% required dialysis. Patients with prior abnormal renal function had a 41.7% incidence of ARD, and 8.3% required dialysis as a result of angiography. Vigorous intravenous hydration was used in all patients but did not completely prevent renal problems. Two risk factors not previously emphasized were the injection site (higher risk with abdominal aortic studies) and presence of congestive heart failure requiring treatment with digoxin. Other notable risk factors included contrast load and age. These results emphasized that even with modern contrast agents and application of current concepts of treatment, there remains a risk of renal injury with major angiography.

Fate of aortic graft removal.

Reoperation to remove an aortic graft was performed in 18 patients. The need for removal was infection in the majority. A changing flora was seen in aortic graft infection with gram-negative organisms predominating. Despite a standardized approach with total graft removal, aortic closure, and extraanatomic reconstruction, amputation and mortality rates remain unacceptably high. A new approach to this problem is needed, and further trials with autogenous reconstruction appear warranted.

Observations on the rate and mechanism of hemolysis in individuals with Hb Zürich [His E7(63)beta leads to Arg]: II. Thermal denaturation of hemoglobin as a cause of anemia during fever.

Individuals with unstable hemoglobins may become more anemic during episodes of intercurrent viral or bacterial infections. Pathophysiologic mechanisms that are responsible for this phenomenon have not been elucidated. Recently we observed a patient with Hb Zürich [His E7(63)beta leads to Arg] whose anemia worsened during a febrile episode characterized by temperatures ranging between 40 degrees and 41 degrees C, splenomegaly, and the appearance of Heinz bodies in the circulating erythrocytes. There was no history of self-medication and no drugs were administered during hospitalization. To determine the effect of a 3 degrees to 4 degrees temperature elevation above the physiologic range on the rate and degree of Heinz body formation, normal (Hb A) and Hb Zürich bloods were incubated in vitro at 4 degrees C, 37 degrees C, and 41 degrees C for 3, 6, 12, and 24 hours and stained for two minutes at the end of each incubation period with rhodanile blue. No Heinz bodies appeared at 4 degrees C. The rate of Heinz body formation was significantly greater in Hb Zürich than normal blood, both at 37 degrees C and 41 degrees C. These observations suggest that in vivo exposure of red cells to temperatures in the biologic range of fever may contribute to the worsening of anemia that occurs during infections in individuals with unstable hemoglobins. Incubating whole blood at 41 degrees C for three hours and staining with rhodanile blue for two minutes appears to be a simple and effective screening test for Hb Zürich and possibly the other unstable hemoglobins. Also the technique is semi-quantitative and may be useful as a research tool for defining factors altering the in vivo stability of the unstable hemoglobins.