Hemodynamic Monitoring In The Cardiac Surgical Patient: Comparison of Three Arterial Catheters

OBJECTIVE

Systemic systolic (SAP) and mean (MAP) arterial pressure monitoring is the cornerstone in hemodynamic management of the cardiac surgical patient, and the radial artery is the most common site of catheter placement. The present study compared 3 different arterial line procedures. It is hypothesized that a 20-G 12.7- cm catheter inserted into the radial artery will be equal to a 20-G 12.7- cm angiocath placed in the brachial artery, and superior to a 20-G 5.00 cm angiocath placed in the radial artery.

DESIGN

A prospective randomized control study was performed.

SETTING

Single academic university hospital.

PARTICIPANTS

Adult patients ≥18 years old undergoing nonemergent cardiac surgery using cardiopulmonary bypass (CPB).

INTERVENTIONS

After approval by the Rhode Island Hospital institutional review board, a randomized prospective control study to evaluate 3 different peripheral intraarterial catheter systems was performed: (1) Radial Short (RS): 20-G 5- cm catheter; (2) Radial Long (RL): 20-G 12- cm catheter; and (3) Brachial Long (BL): 20-G 12- cm catheter.

MEASUREMENTS AND RESULTS

Gradients between central aortic and peripheral catheters (CA-P) were compared and analyzed before CPB and 2 and 10 minutes after separation from CPB. The placement of femoral arterial lines and administration of vasoactive medications were recorded. After exclusions, 67 BL, 61 RL, and 66 RS patients were compared. Before CPB, CA-P SAP and MAP gradients were not significant among the 3 groups. Two minutes after CPB, the CA-P SAP gradient was significant for the RS group (p = 0.005) and insignificant for BL (p = 0.47) and RL (p = 0.39). Two-group analysis revealed that CA-P SAP gradients are similar between BL and RL (p = 0.84), both of which were superior to RS (p = 0.02 and p = 0.04, respectively). At 10 minutes after CPB, the CA-P SAP gradient for RS remained significant (p = 0.004) and similar to the gradient at 2 minutes. The CA-P SAP gradients increased from 2 to 10 minutes for BL (p = 0.13) and RL (p = 0.06). Two minutes after CPB, the CA-P MAP gradients were significant for the BL (p = 0.003), RL (p < 0.0001), and RS (p < 0.0001) groups. Two-group analysis revealed that the CA-P MAP gradients were lower for the BL group compared with the RL (p = 0.054) and RS (p< 0.05) groups. Ten minutes after CPB, the CA-P MAP gradients in the RL and RS groups remained significant (p < 0.0001) and both greater than the BL group (p = 0.002). A femoral arterial line was placed more frequently in the RS group (8/66 = 12.1%) than in the RL group (3/61 = 4.9%) and the BL group (2/67 = 3.0%). Vasopressin was administered significantly more frequently in the RS group.

CONCLUSION

Regarding CA-P SAP gradients, the RL group performed equally to the BL group, both being superior to RS. Regarding CA-P MAP gradients, BL was superior to RL and RS. Clinically, femoral line placement and vasopressin administration were fewer for the BL and RL groups when compared with the RS group. This study demonstrated the benefits of a long (12.7 cm) 20- G angiocath placed in the radial artery.

Caught by POCUS: Post-TAVR Pericardial Effusion

Point-of-care ultrasound (POCUS) is becoming increasingly popular in the field of anesthesiology and is being incorporated into anesthesia resident education. Ultrasound provides a portable, quick, and inexpensive diagnostic tool to help guide clinicians in their decision making and management of medically complex patients. One important utilization of POCUS is helping to guide management of undifferentiated hypotension. We present a case of a patient who underwent a Transcatheter Aortic Valve Replacement (TAVR) procedure who then suffered from hypotension in the post-anesthesia care unit (PACU). POCUS was used to help identify the cause of the patient's hypotension and led to the diagnosis of a pericardial effusion.

1363 ‘FRAILTY AS AN ADJECTIVE RATHER THAN A DIAGNOSIS’ - THE IDENTIFICATION OF FRAILTY IN PRIMARY CARE: A QUALITATIVE INTERVIEW STUDY

Introduction

In 2017 NHS England introduced proactive identification of frailty into the General Practitioners (GPs) Contract. There is currently little information as to how this policy has been operationalised by front-line clinicians, their working understanding of frailty, or perceptions of impact on patient care. Evidence from international settings suggests primary care clinicians may have mixed interpretations of frailty, with important implications for their willingness to support different frailty interventions. We aimed to explore the conceptualisation of frailty, and how community-dwelling frail older adults are identified in primary care.

Methods

Semi-structured interviews were conducted with primary care staff across England, including GPs, physician associates, nurse practitioners, paramedics and pharmacists. Thematic analysis was facilitated through NVivo (Version 13).

Results

31 practitioners participated (12 GPs, 19 non-GPs). Frailty was seen as difficult to define, with uncertainty in its value as a medical diagnosis. The most common working model was the frailty phenotype, associated with deterioration at end of life. There was a mixture of formal and informal processes for identifying frailty. A few practices had embedded population screening and structured reviews. Informal processes included use of ‘housebound’ as a proxy for frailty, identification through chronic disease and medication reviews, and holistic assessment through good continuity of care. Many clinicians described poor accuracy of the electronic Frailty Index, yet it was commonly used to grade frailty during protocolised chronic disease reviews. The Clinical Frailty Score, in contrast, was felt to be easy to use and interpret, but inconsistently recorded within electronic health records. Most clinicians favoured better tools for identifying frailty, alongside resources to support these individuals.

Conclusions

Concepts of frailty in primary care differ. Identification is predominantly ad-hoc, opportunistic and associated with terminal illness. A more cohesive approach to frailty, relevant to primary care, together with better diagnostic tools, may encourage wider recognition.

1367 RECOGNITION AND MANAGEMENT OF ACUTE FUNCTIONAL DECLINE: A QUALITATIVE INTERVIEW STUDY WITH UK CARE HOME STAFF

Introduction

Older people living in care homes sometimes experience episodes of acute functional decline. These represent a diagnostic challenge to healthcare professionals and can result in antibiotic prescriptions or hospital admissions, though this may not always the most appropriate management strategy. We aimed to understand how episodes of acute functional decline are recognised, managed and escalated by care home staff in the UK.

Method

This was a qualitative interview study with UK care home staff, including managers, nurses and carers. Participants were recruited through advertisements circulated via email, social media and word of mouth. Semi-structured interviews were conducted over the phone between January 2021 and April 2022. Thematic analysis was facilitated by NVivo software.

Results

25 care home staff were interviewed. Participants described feeling confident in recognising when residents were less well than usual, especially if they knew them well. However, they sometimes felt it was difficult to differentiate between an ‘off day’ and something more significant. Most participants talked about clear early communication amongst the team to flag a resident of concern. Initial management steps in the care home included checking clinical observations and doing a urine dipstick. Many participants talked about considering the underlying cause for deterioration. Some participants felt comfortable monitoring residents for a few days themselves or trying a simple intervention. Others preferred escalating directly to outside clinical support. Triggers for escalation included perceived severity of illness, gut feeling or failure to respond to initial supportive management.

Conclusions

These results highlight the skill base of care home staff. However, it has also helped to identify areas for additional support and training including the use and interpretation of the urine dipstick. The findings of this study are being used to inform the design of a feasibility prospective cohort study of UK care home residents.

A Pilot Study to Assess the Clinical Onset of IV Heparin in Interventional Cardiology and Cardiac Surgery

OBJECTIVES

To determine the onset of heparin anticoagulation, using 2 different measures of activated clotting times (ACT), thromboelastography (TEG; R-time), and anti-Xa levels, after administering low- (100 U/kg) and high- (300 U/kg) dose intravenous (IV) heparin to patients undergoing transcatheter aortic valve replacement (TAVR) and cardiac surgery, respectively.

DESIGN

Prospective study.

SETTING

Single academic institution.

PARTICIPANTS

Patients with normal baseline coagulation presenting for TAVR or cardiac valve surgery.

INTERVENTIONS

Coagulation studies were performed at baseline, 30 seconds, 90 seconds, and 180 seconds after IV heparin administration. The tests included iSTAT (iACT) and Hemochron ACT (hACT), TEG R-Time, and anti-Xa levels. At the authors' institution, anti-Xa is the preferred measure of heparin anticoagulation when time permits. ACT, a rapid point- of-care test, is used to assess intraprocedural anticoagulation.

MEASUREMENTS AND MAIN RESULTS

After both low- and high-dose heparin, there are peak increases in ACT and anti-Xa at 30 seconds, followed by a decline at 90 seconds and plateau at 180 seconds. The TEG R-time remained elevated (>80 minutes) throughout. For TAVR cases, all anti-Xa was >1.5 IU/mL, and was associated with an iACT >180 seconds and an hACT >200 seconds. For cardiac valve surgery cases, all anti-Xa was >2.4 and associated with an iACT >420 seconds and and hACT >340 seconds. Compared with hACT, iACTs were significantly lower at all time points after low-dose heparin, but not after high-dose heparin.

CONCLUSIONS

In this pilot study, heparin anticoagulation was detected as early as 30 seconds after IV administration, based on ACT, anti-Xa levels, and TEG R-time.

Transesophageal echocardiographic imaging of the coronary sinus: a retrospective analysis of mid-esophageal views and a novel transgastric view

Background

Transesophageal echocardiographic imaging plays an important role in assessing coronary sinus anatomy prior to placement of a retrograde cardioplegia cannula. The coronary sinus can be imaged in the long axis by advancing the TEE probe from the mid-esophageal 4-chamber view or using a modified mid-esophageal bicaval view, while a short axis view can be obtained in the mid-esophageal 2-chamber view. While use of a transgastric view is only briefly mentioned in the literature as an alternative to mid-esophageal views, the authors commonly include it in our comprehensive transesophageal echocardiographic exam of the coronary sinus. This study examines the various imaging strategies. We hypothesize that the transgastric view offers comparable coronary sinus imaging to the mid-esophageal views.

Methods

After approval by our institutional review board, the intraoperative transesophageal echocardiographic exams for 50 consecutive elective cardiac surgical patients with a comprehensive echocardiographic assessment of the coronary sinus were retrospectively reviewed and analyzed to evaluate imaging of the coronary sinus in the various views. For each view, we noted and recorded if the coronary sinus and coronary sinus cannula were visualized. Statistical analysis required pairwise comparisons between each of the 4 views. P values were calculated using McNemar’s Exact test.

Results

Both the coronary sinus and coronary sinus cannula were visualized a majority of the time for each view. There was no statistically significant difference between each view in its ability to visualize the coronary sinus, nor was there a statistically significant difference between each view in its ability to visualize the coronary sinus cannula.

Conclusions

Use of a transgastric window provides the echocardiographer with an effective alternate modality for imaging the coronary sinus when mid-esophageal views are limited.

Flip Your Perspective: Dextrocardia and its Effect on Monitoring and Management

Dextrocardia is a rare congenital disorder characterized by an anatomically flipped heart that is positioned in the right instead of the left side of the thorax. Anatomical variants, such as this, are vital to be aware of as they can alter patient monitoring and management. In this case report, we describe a patient with dextrocardia whose anatomy affected intraoperative monitoring while undergoing a successful aortic valve replacement surgery.

Clinical Reliability of point-of-care tests to support community based acute ambulatory care

OBJECTIVE

To ensure clinicians can rely on point-of-care testing results, we assessed agreement between point-of-care tests for creatinine, urea, sodium, potassium, calcium, Hb, INR, CRP and subsequent corresponding laboratory tests.

PARTICIPANTS

Community-dwelling adults referred to a community-based acute ambulatory care unit.

INTERVENTIONS

The Abbott i-STATTM (Hb, clinical chemistry, INR) and the AfinionTM Analyser (CRP) and corresponding laboratory analyses.

OUTCOMES

Agreement (Bland-Altman) and bias (Passing-Bablok regression).

RESULTS

Among 462 adults we found an absolute mean difference between point-of-care and central laboratory analyses of 6.4g/L (95%LOA -7.9 to +20.6) for haemoglobin, -0.5mmol/L (95%LOA -4.5 to +3.5) for sodium, 0.2mmol/L (95%LOA -0.6 to +0.9) for potassium, 0.0mmol/L (95%LOA -0.3 to +0.3) for calcium, 9.0 μmol/L (95%LOA -18.5 to +36.4) for creatinine, 0.0mmol/L (95%LOA -2.7 to +2.6) for urea, -0.2 (95%LOA -2.4 to +2.0) for INR, -5.0 mg/L (95%LOA -24.4 to +14.4) for CRP.

CONCLUSIONS

There was acceptable agreement and bias for these analytes, except for haemoglobin and creatinine.

Genome sequence of vanilla distortion mosaic virus infecting Coriandrum sativum

The 9573-nucleotide genome of a potyvirus was sequenced from a Coriandrum sativum plant from India with viral symptoms. On analysis, this virus was shown to have greater than 85 % nucleotide sequence identity to vanilla distortion mosaic virus (VDMV). Analysis of the putative coat protein sequence confirmed that this virus was in fact VDMV, with greater than 91 % amino acid sequence identity. The genome appears to encode a 3083-amino-acid polyprotein potentially cleaved into the 10 mature proteins expected in potyviruses. Phylogenetic analysis confirmed that VDMV is a distinct but ungrouped member of the genus Potyvirus.

Echocardiographic quantification of mitral valvular response to myocardial revascularization

AIMS AND OBJECTIVES

Mild and/or moderate ischemic mitral regurgitation (IMR) may resolve after isolated coronary artery bypass grafting (CABG). It has been shown that the loss of saddle shape of the mitral valve is associated with IMR and is determined by an increase in the nonplanarity angle (NPA). The aim of this prospective, observational study was to test the hypothesis that NPA might decrease immediately after CABG alone in patients with mild to moderate IMR.

MATERIALS AND METHODS

This prospective, observational study was conducted in an academic, tertiary care hospital. Twenty patients underwent 2D and 3D transoesophageal echocardiography (TEE) and mitral valve assessment before and immediately after the CABG. NPA, circularity index, and other geometric variables were obtained. They were compared using paired t test. The SPSS (Version 15.0, Chicago, IL, USA) was used for statistical analysis. P <0.05 was considered significant.

RESULTS

The NPA was similar in the pre- and post-bypass periods (148° ± 15°, 148° ± 19°, P = 0.88). Circularity index (0.93 ± 0.13, 0.97 ± 0.11, P = 0.41) also was similar.

CONCLUSIONS

There was no change in the mitral valve NPA with revascularization alone in patients with mild or moderate IMR. Mitral valve does not change its planarity (NPA) with revascularization alone in patients with IMR.

Evidence for non-communicable diseases: analysis of Cochrane reviews and randomised trials by World Bank classification

INTRODUCTION

Prevalence of non-communicable diseases (NCDs) is increasing globally, with the greatest projected increases in low-income and middle-income countries. We sought to quantify the proportion of Cochrane evidence relating to NCDs derived from such countries.

METHODS

We searched the Cochrane database of systematic reviews for reviews relating to NCDs highlighted in the WHO NCD action plan (cardiovascular, cancers, diabetes and chronic respiratory diseases). We excluded reviews at the protocol stage and those that were repeated or had been withdrawn. For each review, two independent researchers extracted data relating to the country of the corresponding author and the number of trials and participants from countries, using the World Bank classification of gross national income per capita.

RESULTS

797 reviews were analysed, with a reported total number of 12 340 trials and 10 937 306 participants. Of the corresponding authors 90% were from high-income countries (41% from the UK). Of the 746 reviews in which at least one trial had met the inclusion criteria, only 55% provided a summary of the country of included trials. Analysis of the 633 reviews in which country of trials could be established revealed that almost 90% of trials and over 80% of participants were from high-income countries. 438 (5%) trials including 1 145 013 (11.7%) participants were undertaken in low-middle income countries. We found that only 13 (0.15%) trials with 982 (0.01%) participants were undertaken in low-income countries. Other than the five Cochrane NCD corresponding authors from South Africa, only one other corresponding author was from Africa (Gambia).

DISCUSSION

The overwhelming body of evidence for NCDs pertains to high-income countries, with only a small number of review authors based in low-income settings. As a consequence, there is an urgent need for research infrastructure and funding for the undertaking of high-quality trials in this area.

Wireless recording of the calls of Rousettus aegyptiacus and their reproduction using electrostatic transducers

Bats are capable of imaging their surroundings in great detail using echolocation. To apply similar methods to human engineering systems requires the capability to measure and recreate the signals used, and to understand the processing applied to returning echoes. In this work, the emitted and reflected echolocation signals of Rousettus aegyptiacus are recorded while the bat is in flight, using a wireless sensor mounted on the bat. The sensor is designed to replicate the acoustic gain control which bats are known to use, applying a gain to returning echoes that is dependent on the incurred time delay. Employing this technique allows emitted and reflected echolocation calls, which have a wide dynamic range, to be recorded. The recorded echoes demonstrate the complexity of environment reconstruction using echolocation. The sensor is also used to make accurate recordings of the emitted calls, and these calls are recreated in the laboratory using custom-built wideband electrostatic transducers, allied with a spectral equalization technique. This technique is further demonstrated by recreating multi-harmonic bioinspired FM chirps. The ability to record and accurately synthesize echolocation calls enables the exploitation of biological signals in human engineering systems for sonar, materials characterization and imaging.

Six-degree-of-freedom whole-body vibration exposure levels during routine skidder operations

This research focuses on quantifying six-degree-of-freedom (6-DOF) whole-body vibration (WBV) exposure levels that occur in Northern Ontario skidders during routine field operating tasks. 6-DOF vibration running root-mean-square (RMS) acceleration levels at the operator/seat interface were determined for eight skidders while driving loaded, driving unloaded, picking up a load, dropping off a load and ploughing logs under field operating conditions. The acceleration data were weighted in accordance with ISO 2631-1:1997 and evaluated for both health and comfort outcomes. The mean running RMS weighted translational and rotational accelerations all exceeded 0.36 m/s(2) and 0.14 rad/s(2). The greatest average accelerations occurred while driving unloaded with this condition displaying translational vibration total values (VTV) that exceeded the upper limit of the ISO 2631-1:1997 health caution zone within an average of 2.3 h. Utilizing 6-DOF VTV, virtually all operating conditions would be designated as uncomfortable. STATEMENT OF RELEVANCE: This study provides one of the most comprehensive reports on vibration exposures in seated vehicle operators. The results are geared towards ergonomists with discussions on health effects and measurement concerns, while providing the raw vibration exposure data that will be useful to vehicle, component and vibration sensor designers.

Modelling the bioelectric behaviour of halo pin-patient structures during magnetic resonance imaging

Bioelectric compatibility of electrically conductive halo fixation devices and magnetic resonance (MR) imaging has been largely based on resulting image quality. Previous studies have focused primarily on improving image quality and, although the electrical characteristics of the system during imaging may have been noted, they have not been studied in depth. Utilizing both a theoretical and experimental approximation, this study focuses on the bioelectric characteristics of the pin-patient structures typically enountered in clinical halo fixation systems. Results indicate that the halo pin-patient system can be modelled using a resistor-inductor-capacitor circuit and that simple attempts at improving compatibility through increasing interface resistance by the use of insulated pins may not be an effective approach to improving halo instrumentation compatibility with new, stronger magnetic and higher-frequency resonance imaging systems.

Laterality effects in the recognition of depth-rotated novel objects

The dissociable neural subsystems theory proposes that left-hemisphere (LH) performance is dominated by a viewpoint-invariant (VI) recognition subsystem, whereas right-hemisphere (RH) performance is dominated by a viewpoint-dependent (VD) subsystem (Marsolek, 1999). Studies supporting this theory have used familiar objects and, therefore, may have been confounded by characteristics beyond perceptual features. Experiment 1, a lateralized sequential-matching task with novel objects, showed VD recognition in both hemispheres. In Experiment 2, some participants learned semantic associations for four novel objects, whereas others were exposed to the novel objects without the semantic associations. Both groups later performed a depth-rotated lateralized sequential-matching task. The participants who had learned semantic associations showed greater VD performance in the RH than in the LH; however, the participants in the control group showed equivalent VD performance in both hemispheres. The results suggest that hemispheric differences in VD performance may be partially attributable to an LH advantage for semantic processing.

Localisation of the subthalamic nucleus using Radionics Image Fusion and Stereoplan combined with field potential recording. A technical note

Subthalamic nucleus stimulation is an effective therapy for alleviating parkinsonian tremor, rigidity and bradykinesia. Although microelectrode recording is said to be essential for accurate targeting, this often prolongs the operation and the multiple recording tracts required may increase the incidence of complications, particularly haemorrhage. We describe a technique for implantation of deep brain electrodes in the subthalamic nucleus using MRI/CT fusion for anatomical localisation followed by bipolar recording of focal field potentials via the implanted stimulating electrode for neurophysiological confirmation of the stimulation site. The technique is effective, safe and requires much less time, and can be used as an alternative method to microelectrode recording.

The generation and detection of longitudinal guided waves in thin fibers using a conical transformer

This paper describes a technique to couple ultrasonic energy from a piezoceramic disc transducer into a fiber waveguide to induce longitudinal propagation. A polymer cone is utilized to bond the fiber waveguide onto the surface of the disc and to behave as a mechanical transformer, converting lateral displacements at its base into longitudinal displacements at its apex. Wideband finite element analysis (FEA) results are provided to show that the bond efficiently couples the radial modes of a disc transducer into fiber waveguides for longitudinal mode excitation. Furthermore, narrowband FEA is utilized to investigate how the geometry and material properties of the bond and waveguide influence the coupling efficiency. The technique is then quantified in terms of signal-to-coherent noise ratio (SCNR), reflecting its ability to generate the desired longitudinal waveguide mode and reject erroneous modes. Finally, design parameters are outlined for the successful implementation of this technique.

Micromachining of a piezocomposite transducer using a copper vapor laser

A 1-3 piezocomposite transducer with front face dimensions of 2 x 2 mm has been micromachined using a copper vapor laser. The device consists of PZT5A piezoceramic pillars with a 65-micron pitch suspended in a low viscosity thermosetting polymer. The kerf width is 13 microns, and the transducer thickness is 170 microns, making the device suitable for ultrasonic reception at frequencies close to 10 MHz.

Seroepidemiology and molecular epidemiology of Kaposi's sarcoma-associated herpesvirus among Jewish population groups in Israel

BACKGROUND

The incidence of classic Kaposi's sarcoma among Jews in Israel is among the highest in the developed world. Kaposi's sarcoma-associated herpesvirus (KSHV or human herpesvirus 8) is causally linked to Kaposi's sarcoma. Very little is known about the prevalence of KSHV in the Middle East or about the modes of transmission in Mediterranean countries.

METHODS

From 1992 through 1995, sera were obtained from 1648 adults who had tested positive for hepatitis B virus (HBV) surface antigen 20 years earlier at blood donations; sera were also obtained from 2403 of their family members. All sera were tested for anti-KSHV antibodies with the use of an indirect immunofluorescence assay. To analyze the effects of various factors on the risk of KSHV infection for both the HBV-positive cohort and their families, logistic regression for cluster data and generalized estimating equations were used. All statistical tests were two-sided.

RESULTS

Among family members, the seroprevalence of antibodies against KSHV was 9.9% (95% confidence interval [CI] = 8.7% to 11.1%); among the former blood donors who had tested positive for hepatitis B, it was 22% (95% CI = 19.9% to 24.1%). Overall, the best predictor of KSHV status was the place of birth. The most important risk factors found for both husband and wife to test KSHV positive were their own places of birth and their spouse's seropositivity. For a child to test positive, the most important risk factor was maternal seropositivity.

CONCLUSIONS

The crude prevalence rate of KSHV among the Jewish population in Israel is 9.9%. Important routes of KSHV transmission in the families studied are spouse to spouse and mother to child. The presence of KSHV in Jews in Israel of all ethnic origins and their high incidence of reported Kaposi's sarcoma suggest that KSHV was introduced into the Jewish population prior to the major Diaspora.

Wave propagation in 0-3/3-3 connectivity composites with complex microstructure

This work presents a study of the properties of particulate composites. The whole range of particle volume fraction (0-1) and ideal 0-3, 3-3 and intermediate 0-3/3-3 connectivities are analysed. Two different approaches to produce a realistic model of the complex microstructure of the composites are considered. The first one is based on a random location of mono-dispersed particles in the matrix; while the second incorporates a size distribution of the particles based on experimental measurements. Different particle shapes are also considered. A commercial finite element package was used to study the propagation of acoustic plane waves through the composite materials. Due to the complexity of the problem, and as a first step, a two-dimensional model was adopted. The results obtained for the velocity of sound propagation from the finite element technique are compared with those from other theoretical approaches and with experimental data. The study validates the use of this technique to model acoustic wave propagation in 0-3/3-3 connectivity composites. In addition, the finite element calculations, along with the detailed description of the microstructure of the composite, provide valuable information about the micromechanics of the sample and the influence of the microstructure on macroscopic properties.

Diffusable growth factors induce bladder smooth muscle differentiation

Bladder smooth muscle differentiation is dependent on the presence of bladder epithelium. Previously, we have shown that direct contact between the epithelium and bladder mesenchyme (BLM) is necessary for this interaction. In this study, we tested the hypothesis that bladder smooth muscle can be induced via diffusable growth factors. Fourteen-day embryonic rat bladders were separated into bladder mesenchyme (prior to smooth muscle differentiation) and epithelium by enzymatic digestion and microdissection. Six in vitro experiments were performed with either direct cellular contact or no contact (1) 14-d embryonic bladder mesenchyme (BLM) alone (control), (Contact) (2) 14-d embryonic bladders intact (control), (3) 14-d embryonic bladder mesenchyme combined with BPH-1 cells (an epithelial prostate cell line) in direct contact, (4) 14-d embryonic bladder mesenchyme with recombined bladder epithelium (BLE) in direct contact, (No Contact) (5) 14-d embryonic bladder mesenchyme with BPH-1 prostatic epithelial cells cocultured in type 1 collagen gel on the bottom of the well, and (6) 14-d embryonic bladder mesenchyme with BPH-1 epithelium cultured in a monolayer on a transwell filter. In each case the bladder tissue was cultured on Millicell-CM 0.4-microm membranes for 7 d in plastic wells using serum free medium. Growth was assessed by observing the size of the bladder organoids in histologic cross section as well as the vertical height obtained in vitro. Immunohistochemical analysis of the tissue explants was performed to assess cellular differentiation with markers for smooth muscle alpha-actin and pancytokeratin to detect epithelial cells. Control (1) bladder mesenchyme grown alone did not exhibit growth or smooth muscle and epithelial differentiation. Contact experiments (2) intact embryonic bladder, (3) embryonic bladder mesenchyme recombined with BPH-1 cells, and (4) embryonic bladder mesenchyme recombined with urothelium each exhibited excellent growth and bladder smooth muscle and epithelial differentiation. Both noncontact experiments (5) and (6) exhibited growth as well as bladder smooth muscle and epithelial differentiation but to a subjectively lesser degree than the contact experiments. Direct contact of the epithelium with bladder mesenchyme provides the optimal environment for growth and smooth muscle differentiation. Smooth muscle growth and differentiation can also occur without direct cell to cell contact and is not specific to urothelium. This data supports the hypothesis that epithelium produces diffusable growth factors that induce bladder smooth muscle.

Domestic and personal accidents. Prevention in the absence of professional supervision

This paper provides a review of a selection of recent papers, most of which derive from presentations given at the 4th World Conference on Injury Prevention and Control or the 6th International Conference on Product Safety Research, both of which took place in Amsterdam in May 1998. What all the accidents studied in these papers have in common is the absence of professional supervision. Everyone immediately involved in the incident--whether as injured party, unintended cause or informal supervisor is an 'amateur'. It is proposed that the term 'domestic and personal accidents' should be used to describe this group of accidents, the study of which has been neglected in comparison to transport and occupational injuries. It is argued that domestic and personal activities are more heterogeneous than ones with an element of professional supervision and are therefore more difficult to prevent. Nevertheless examples are given of where 'horizontal' approaches to analysis and prevention of these accidents have proved possible.

Beam profile measurements and simulations for ultrasonic transducers operating in air

This paper outlines a method that has been implemented to predict and measure the acoustic radiation generated by ultrasonic transducers operating into air in continuous wave mode. Commencing with both arbitrary surface displacement data and radiating aperture, the transmitted pressure beam profile is obtained and includes simulation of propagation channel attenuation and where necessary, the directional response of any ultrasonic receiver. The surface displacement data may be derived directly, from laser measurement of the vibrating surface, or indirectly, from finite element modeling of the transducer configuration. To validate the approach and to provide experimental measurement of transducer beam profiles, a vibration-free, draft-proof scanning system that has been installed within an environmentally controlled laboratory is described. A comparison of experimental and simulated results for piezoelectric composite, piezoelectric polymer, and electrostatic transducers is then presented to demonstrate some quite different airborne ultrasonic beam-profile characteristics. Good agreement between theory and experiment is obtained. The results are compared with those expected from a classical aperture diffraction approach and the reasons for any significant differences are explained.

The radiation field characteristics of piezoelectric polymer membrane transducers when operating into air

This paper describes the evaluation of the radiation field characteristics of PVDF membrane transducers, whereby the active area is defined by an appropriate electrode pattern when operating into air. Measurement, including conventional scanning of the fields and laser vibrometry, is supplemented by finite element modeling over the frequency range 500 kHz to 1.1 MHz. Contrary to expectation, the surface displacements are nonuniform, giving rise to premature axial focusing of the field. This is shown to be caused by generation of the zero order symmetrical Lamb wave, arising from the electric field discontinuity at the electrode boundary of the transducer.

Investigation into the effects of modification of the passive phase for improved manufacture of 1-3 connectivity piezocomposite transducers

The 1-3 connectivity composite transducers comprise active piezoceramic pillars within a passive polymer matrix. The first stage in manufacturing the 1-3 material is to produce a bristle block (comprising a solid stock of active material with protruding pillars) by injection moulding or by dicing a piece of ceramic using precision sawing equipment. The bristle block is filled with a reactive polymer liquid that produces the passive polymer phase, and the filled block is machined to the desired dimensions. For optimum performance, the polymer phase should have complementary interaction with the ceramic phase as well as imparting dimensional stability. Epoxy-based polymers are the most usual passive materials because of their low viscosity in the uncured state and solvent resistance, coupled with their excellent adhesive, mechanical, and electrical properties. However, the curing of epoxy resins results in shrinkage of the polymer matrix and internal stress within the passive phase. This can lead to prestressing of the active ceramic material, distortion of pillars, reduction in the parallelism between the sides of pillars, acid, in certain circumstances, warpage of transducers. This is particularly evident when the solid stock in the bristle block is relatively thin. This paper reports the in situ modification of epoxy in the bristle block by UV-based low temperature polymerization of acrylate monomers within the epoxy matrix prior to polymerization of the epoxy resin. Internal stress measurements are presented to quantify the influence of this modification via a reduction of internal stress within the polymer matrix. Results from finite element analysis emphasise the conclusions of the experimental work, and examples of manufactured devices are presented. Composite transducer performance is assessed by laser measurement of surface displacement profiles, and a 50% improvement in surface displacement magnitude was observed for the modified devices.

Ultrasonic arrays for monitoring cracks in an industrial plant at high temperatures

A piezoelectric linear array structure has been designed to operate at temperatures up to 400 degrees C for nondestructive testing of steel components of a hot industrial plant. It is intended that these arrays be fixed permanently to the test subject so that known defects can be monitored by comparing measurements taken over a period of time without needing to shut down the plant. The arrays are used in pairs: the transmitter is a phased array producing a variable angle steered beam, and a second array is used for receiving. The defect can be identified from a series of scans collected from individual elements of the second array. A simple monolithic array structure was used, based on a single crystal of lithium niobate and operating in the frequency range 3 to 5 MHz. Prototype devices have 64 elements on a 0.5 mm pitch. Simulated defects in steel blocks have been scanned at high temperatures to illustrate the arrays' capability for nondestructive testing. The results suggest an accuracy better than 1 mm in finding the location of crack tips.

Generation and reception of ultrasonic guided waves in composite plates using conformable piezoelectric transmitters and optical-fiber detectors

A condition monitoring nondestructive evaluation (NDE) system, combining the generation of ultrasonic Lamb waves in thin composite plates and their subsequent detection using an embedded optical fiber system is described. The acoustic source is of low profile with respect to the composite plate thickness, surface conformable, and able to efficiently launch a known Lamb wave mode, at operating frequencies between 100 and 500 kHz, over typical propagation distances of 100 to 500 mm. It incorporates both piezocomposite technology and interdigital design techniques to generate the fundamental symmetrical Lamb wave mode in both metallic and carbon-fiber composite plates. Linear systems and finite element modeling techniques have been used to evaluate the operation of the transducer structure, and this is supplemented by experimental verification of the simulated data. An optical fiber, either bonded to the surface or embedded across the length of the composite plate samples, is used to detect the propagating ultrasonic Lamb waves. Single mode silica fiber has been used in conjunction with a portable 633 nm Mach-Zehnder interferometer for signal demodulation and subsequent data acquisition. This hybrid system is shown to generate and detect the fundamental symmetrical Lamb wave (s(0)) in both carbon-fiber and glass-fiber reinforced composite plates. Importantly, the system signal-to-noise ratio (SNR) associated with the acoustic source compares favorably with s(0) Lamb wave generation using a conventional transducer and angled perspex wedge arrangement.

Development of a PVDF membrane hydrophone for use in air-coupled ultrasonic transducer calibration

This work describes the use of a polyvinylidene fluoride (PVDF) membrane hydrophone for application in air-coupled transducer calibration. A one-dimensional theoretical analysis is used to demonstrate the potential and performance of PVDF as a hydrophone material over the frequency range 100 kHz to 5 MHz included in the evaluation is the influence of deposited metallic electrode layers on the sensitivity of the material. Experimental validation over the restricted range 400 kHz to 1 MHz is provided by a coplanar 0.028 mm thick membrane hydrophone in conjunction with a custom built 1-3 piezocomposite transmitter. Calibration of the membrane hydrophone is performed by employing a standard hydrophone that has been calibrated to a primary standard in a water medium. Justification for such an approach is presented within the theoretical analysis which provides a close correlation with experimental data. The generation of Lamb waves at critical angles in the PVDF and their subsequent influence on the directional response of membrane hydrophones operating in air is also addressed. A method for partial suppression of the Lamb waves, based around perforation of the membrane (either in whole or in part), is evaluated experimentally with reasonable results.

Unidimensional modeling of multi-layered piezoelectric transducer structures

Multi-layered transducer structures offer the potential of improved performance in terms of increased transmit sensitivity, greater bandwidth, and enhanced reception characteristics. Unfortunately, the successful design of such devices is often difficult, owing to the complex interaction between the active piezoelectric layers and passive intermediate interface layers. Furthermore, in many practical applications, the loading effects imposed by the electrical drive circuitry often limit the performance improvements that may be physically realized. This paper describes the development of a comprehensive, unidimensional modeling approach. This model may be employed to facilitate the analysis and subsequent optimization of laminated transducer assemblies. The devices currently under consideration include both piezoceramic and piezopolymer configurations, as well as alternative piezocomposite designs. The effects of varying bondline thickness and the introduction of passive interface layers are examined, as is the influence of the electrical load circuitry on overall system response. The ability to accurately predict the response of stacked piezoelectric structures is demonstrated through extensive comparison of experimental and theoretical responses. This paper concludes by highlighting the important role that modeling plays in the design, fabrication, and optimization of complex multi-layered transducer assemblies.

Surface-bonded and embedded optical fibers as ultrasonic sensors

The effectiveness of surface-bonded and embedded optical fibers for the detection of ultrasonic Lamb waves in 2-3-mm-thick steel, carbon-fiber-reinforced plastic (CFRP) and glass-reinforced plastic (GRP) plates are compared. A novel integrating ultrasonic sensor was achieved using the signal arm of an actively stabilized 633-nm homodyne Mach-Zehnder fiber interferometer which was either bonded directly to the plate surface or spliced to single-mode fibers embedded within a composite plate during manufacture. An embedded fiber is shown to be about 20 times more sensitive to Lamb wave motions than a surface-bonded fiber. However, the latter may be more practical.

Risk of injury per hour of exposure to consumer products

The aim of this study was to determine and compare the risk of injury per hour of use for a range of consumer products. Exposure data was derived from interviewing a large sample of adults about their use of 76 common kitchen, do-it-yourself and household products. This was combined with hospital sample data for injuries involving each product, to yield the risk-of-injury-per-hour-of-use. Powered cutting equipment, access equipment (ladders and scaffolding) and products with sharp blades were shown to have a comparatively high risk, along with cycles, sunbeds, creosote, cement, car jacks and exercise weights. Perceived risk was shown to be a poor basis for priority setting, but a practical guide to priority for preventive action can be provided by "mapping" products on a plot of the risk of injury per hour of use vs the total medical costs of such accidents.

Air-coupled piezoelectric detection of laser-generated ultrasound

A pulsed laser has been used to generate ultrasonic transients in samples of metal and fiber-reinforced polymer composite material. These have been detected using an air-coupled piezoelectric transducer. It is demonstrated that such a transduction system can be used for longitudinal waves in bulk material, Rayleigh waves at solid surfaces and Lamb waves in thin plates.

The human cytomegalovirus 86K immediate early (IE) 2 protein requires the basic region of the TATA-box binding protein (TBP) for binding, and interacts with TBP and transcription factor TFIIB via regions of IE2 required for transcriptional regulation

The 86K immediate early (IE) 2 protein of human cytomegalovirus trans-activates a number of homologous and heterologous promoters, including the cellular promoter for the 70K heat-shock protein (hsp70), and the human immunodeficiency virus long terminal repeat. We have previously shown that IE2 trans-activates these two promoters in a TATA-dependent manner, and that IE2 is able to form a direct contact with TATA-box binding protein (TBP) in vitro. We now show that IE2 binds to the basic repeat region of TBP. In addition IE2 can contact a second general transcription factor, TFIIB. We have mapped the TBP- and TFIIB-binding regions within IE2 and show that these regions overlap, and also lie within parts of the protein previously identified as being required for the trans-activation and autoregulation functions of IE2.

An intelligent ultrasonic inspection system for flooded member detection in offshore structures

An ultrasonic system for automatic underwater inspection of steel jacket offshore installation is described. It is based on the unambiguous detection of water ingress in normally sealed tubular members, thereby providing an indication of through-wall structural failure. A novel transducer design, based on a dual frequency array of 1-3 connectivity thickness drive transducers, is used to provide the required sensitivity and act also as an environmental monitor for input to an expert system, which performs automatic data analysis. Although intended primarily for operation on a remotely operated vehicle, the system may be employed satisfactorily by a driver. A series of test trials is described, and the prototype is shown to perform very well for all intended modes of operation.

Theoretical and experimental evaluation of a two-dimensional composite matrix array

A theoretical and experimental performance appraisal of a two-dimensional, ceramic-epoxy composite matrix array employing 1-3 connectivity is presented. The linear systems approach is used for temporal and spatial simulation of array performance, with specific regard to three-dimensional synthetic aperture imaging in a fluid load medium. Manufacture and experimental evaluation of a prototype array structure, operating at 1.2 MHz and comprising 100 elements arranged as a 10 by 10 matrix, is described. Close agreement between theory and experiment is obtained, providing a clear indication that the low crosstalk, uniformity, and wideband characteristics of composite array elements offer excellent prospects for such imaging applications.

Finite-element analysis of 1-3 composite transducers

The vibrational and electromechanical characteristics of a wide range of 1-3 composite structures, comprising ceramic pillars aligned within a polymer phase, are considered using finite-element analysis. The influence of pillar geometry, ceramic volume fraction, and pillar orientation is described in terms of overall transduction efficiency. It is shown that the finite-element method provides a versatile means of analysis and the results obtained permit a set of useful design guidelines to be developed. In general, a small pillar aspect ratio and a relatively high volume fraction provides the most satisfactory performance, in terms of electromechanical efficiency and uniformity of thickness dilation.