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Electrokinetic (EK) dewatering involves the application of a (direct current) voltage across sewage sludge, driving water under an electrical gradient from the positive electrode (anode) to the negative electrode (cathode). Researchers have shown the technique to be efficient means of driving off water from the sludge, thus improving strength and reducing volume. This paper presents an integrating framework for EK dewatering under constant voltage and constant current conditions, founded on the mathematics of simple electrical circuits and demonstrated by laboratory experimentation. The derived equations and experimental results showed that electroosmotic flow rate decreases with time when dewatering with constant voltage and is constant when constant current conditions are maintained. Having a linear relationship between flow and time, EK dewatering with constant current not only enhances the sludge dewatering efficiency, but also has the advantage of simplifying design procedures.

Injection mould design generally lies on the critical path of a new product development. The design efficiency will have significant impact on the overall lead time of a new product. This paper presents a prototype injection mould-design system using a hybrid case-based reasoning (HCBR) approach. Case-based reasoning (CBR) is a solving paradigm that uses previous episodes on solving problems similar to the problem at hand (the new problem) as the basis for solving the new problem. In this hybrid system, CBR is incorporated with generalized design knowledge, and provides a flexible and comprehensive model of design. The knowledge base of the system would be accessed by mould designers through interactive programs so that their own intelligence and experience could also be incorporated with the total mould design. The approach provides a workable model of mould design system with CBR and knowledge-based expert system intelligent support, which could suggest good and proven design solutions to new design pro...

The rapid growth of Internet and information technologies in recent years provides a solution to support and facilitate collaborative product developments among different geographically distributed enterprises. An effective and feasible tool to aid the collaborative development of injection moulds can be realized by developing an Internet-based mould design system as one of the modules of a collaborative product development system. This paper presents a prototype Internet-based intelligent design system for injection moulds. The architecture of the system consists of an interactive KB mould design system embedded in an Internet environment. A Java-enabled solution together with artificial intelligence techniques is employed to develop such a networked interactive CAD system. In this system, the computational module, the knowledge base module and the graphic module for generating mould features are integrated within an interactive CAD-based framework. The knowledge base of the system would be accessed by mould designers through interactive programs so that their own intelligence and experience could also be incorporated with the total mould design. The approach adopted both speeds up the design process and facilitates design standardization which in turn increases the speed of mould manufacture. A practical case study is presented to illustrate the operations of the Internet-based mould design system.

The use of the Integrated Integration Definition Language 0 (IDEF) descriptive model or similar tools alone in the analysis of complicated processes like the mould-making process usually encounters difficulties due to the complexity of process. A quantitative analysis model thus seems necessary to supplement the IDEF0 tool for better modelling and simulation of complicated processes. The paper proposes to integrate the IDEF0 tool with the coloured Petri nets (CPN) tool for systematic analysis of complicated processes. It introduces an effective modelling and simulation language-hierarchical timed CPN-based workflow nets (HTCPNWF-nets). The rules for translating IDEF0 into HTCPNWF-nets have been developed. After mapping the IDEF0 model onto HTCPNWF-nets, several performance analyses can be achieved by simulation of HTCPNWF-nets model. The proposed methodologies have been successfully applied to the mould-making process. The paper presents the rationales and current progress of the proposed methodologies.

This paper explores the relationship between technology transfer activities and innovation performance with special reference to Chinese industrial firms. It is based on a recent nationwide survey covering 2334 Chinese industrial firms. The impact of technology transfer on their innovative performance was analyzed for all the responded firms and similar analyses also addressed the issue from perspectives of general industrial firms versus high-tech firms, and large firms versus small and medium firms. Several critical types of technology transfer activities were identified and both positive and negative impacts were discussed along with the Pearson correlation analysis and stepwise regression analysis. The study revealed that the innovation activities in Chinese manufacturing firms could not be boosted substantially merely through the acquisition of key equipment and apparatus from abroad. The findings also suggested that Chinese firms should develop their technological absorptive capacity and transformative capacity, and foster technology transfer and communications among trading partners. Moreover, it would be crucial for Chinese firms to stress the nurturing of indigenous innovation capabilities so as to sustain their performance improvement.

Mould design usually lies on the critical path of new product development. The mould-design process generally involves complex and multi-related design problems. The use of the IDEF0 descriptive model or similar tools alone in the analysis of complicated processes like the mould-design process usually encounter difficulties due to the complexity of the process. A quantitative analysis model thus seems necessary to supplement the IDEF0 tool for better modeling and simulation of complicated processes. In this paper, we propose to use the colored Petri nets tool for systematic and through analysis of the complicated mould-design process. We introduce an effective modeling and simulation language-hierarchical timed colored Petri-net-based workflow nets (HTCPNWF-nets). The rules for translating IDEF0 into HTCPNWF-nets have been developed. After mapping IDEF0 model onto HTCPNWF-nets, several performance analyses can be achieved by simulation of HTCPNWF-nets model. The proposed methodologies have been successfully applied to the mold design process.

Researchers and managers have been searching for appropriate methods to explore the relationship between technological innovation capability and competitiveness in recent years. This study attempts to find a systematic quantitative methodology to tackle this problem. In a recent survey covering 182 industrial innovative firms in China, the traditional data envelopment analysis (DEA) model was employed to analyze the data collected. The research results show that only 16% of the enterprises operate on the best-practice frontier and there are some inconsistencies between organizational innovation capability and competitiveness in many enterprises. Decreasing returns to scale were found among about 70% of the inefficient enterprises and increasing returns to scale were found among the remaining 30% of the inefficient enterprises. Thus the internal innovation harmonizing process in these enterprises is considerably inefficient. Based on the restricted ranges of the input/output factors, a multi-objective DEA projection model has also been developed in this study to provide a benchmark for auditing competitiveness. Research results further indicate that there is still much room for enterprises to improve competitiveness in situations of confining score ranges of technological innovation capability and competitiveness.

Most R&D resources in China were allocated to public research institutes/universities until the economic transition of the mid 1990s. To maximize the return from these resources, it is important to have a healthy collaboration between industry and research institutes/universities on industrial innovation. This paper examines that relationship and discusses some empirical evidence on its efficiency with particular reference to industry in Beijing. Following a survey of 950 industrial enterprises, the influences of the collaboration relationship on industrial innovation were analyzed. The main findings indicate that the technology novelty of industrial innovation is positively related to that relationship, i.e. the more the collaboration, the higher the technology novelty of the innovation. However, the collaboration relationship is less efficient in terms of economic performance indicators such as innovation sales and profit ratios, to measure innovation. Moreover, the collaboration relationship i...

The regulation-protected environment of electric utilities has undergone massive changes to open market competition. The protection of the regulatory shield in the past has imposed obstacles and barriers for many electric utilities to change their business emphasis from internal focused to market orientation (MO). In order to face the new challenges, electric utilities have incorporated a large variety of piecemeal change management programmes to change their business emphasis. Many of them have experienced a lot of difficulties in fundamentally transforming themselves from their old ways of doing business. TQM philosophy and principles, targeting the generation of holistic and systematic changes for customer satisfaction, were suggested to be used in guiding the change process in electric utilities towards market orientation through continuous quality improvement. To investigate the possibility of using TQM as an integrative approach to guide market orientation change for electric utilities, an internati...

This research extends our previous investigation of the automation of the preliminary design stage to the layout design stage of the cooling system design process. While the functional aspects of the cooling system are considered during the preliminary design stage, the layout design stage addresses both the functionality and manufacturability of the design. A graph structure is devised to capture a given preliminary design and a graph traversal algorithm is developed to generate candidate cooling circuits from the graph structure. Heuristic search is employed to develop the cooling circuits into the layout designs by generation of tentative manufacturing plans. A framework for fuzzy evaluation of the layout designs is developed to rate the various design alternatives generated. An experimental system is implemented to verify the feasibility of the approach, and examples generated from the system are presented to illustrate the major steps of the automatic design process.

The design of plastic injection moulded part is a highly iterative process and depends largely on the human expertise including product designers, mould designers, manufacturing engineers, who need to possess thorough and broad specific knowledge and experience. The automatic recognition of features for injection moulded parts is the first prominent stage for any automatic design evaluation system. In this paper, features of plastic product are classified in three hierarchical levels of primitive features, complex features and high-level complex features. The proposed method adopts a hybrid approach, which combines the graph theoretic approach with the logic approach. Methodologies of enhanced multi-attributed adjacency graph (EMAAG) and feature-interaction feature graph (FIFG) for automatic extraction of primitive features and complex features of plastic parts, respectively, are presented. The test example shows that the methodologies developed can recognise various features of injection moulded parts successfully.

Minimizing the cost of manufacturing a plastic component is very important in the highly competitive plastic injection molding industry. The current approach of R&D work focuses on optimizing the dimensions of the plastic component, particularly in reducing the thickness of the component during product design, the first phase of manufacturing, in order to minimize the manufacturing cost. This approach treats the component dimensions established in the product design phase as the given input, and uses optimization techniques to reduce the manufacturing cost of mold design and molding for producing the component. In most cases, the current approach provides the correct solution for minimizing the manufacturing cost. However, when the approach is applied to a thin component, typically when miniaturizing products, it has problems finding the true minimum manufacturing cost. This paper analyses the shortcomings of the current approach for handling thin plastic components and proposes a method to overcome them. A worked example is used to illustrate the problems and compare the differences when using the current approach and the new method proposed in the paper.

The demand for high-quality and low-cost products with a short development time for the dynamic global market has forced researchers and industries to focus on various effective product development strategies. Product modelling has been recognised as one of the key factors in determining the success of various product development strategies and for industrial competitiveness now and in the future. This paper proposes a methodology that represents multiview integrated product modelling based on the outcome of a research project on ISO 10303 STEP. The methodology consists of the architecture and information requirements for an integrated product model and a mapping mechanism for the multiview operations of the model, which support product development in a concurrent engineering environment. This methodology will facilitate further research in developing sophisticated product modelling for concurrent product development.

This paper presents a practical prototype knowledge-based system, called IKMOULD, for mould design in the injection moulding process. It attempts to tackle the problem in a practical and integrative way, unlike the stand-alone and mathematical programs which have been developed in the past to solve only a part of the problem. A total quantitative and structured approach is not feasible in dealing with the complex and multirelated design problems generally involved in mould design. In this system, the computational module, the knowledge-based module and the graphic module for generating mould features are integrated within an interactive CAD-based framework. The knowledge base of the system can be accessed by mould designers through interactive programs so that their own intelligence and experience can also be incorporated with the total mould design. The approach adopted both speeds up the design process and facilitates design standardisation which in turn increases the speed of mould manufacture.

SUMMARY Objectives Based on the model by Tsang et al. (2002) which summarized the etiological factors and consequences of depression in elderly with chronic physical illnesses, a randomized clinical trial of a special form of Qigong (The Eight Section Brocades) was conducted to assess if it improved the biopsychosocial health of participants. Design 50 geriatric patients in sub-acute stage of chronic physical illnesses were recruited and randomly assigned into the intervention and control group. The intervention group was given a 12-week period of Qigong practice while the control group was given traditional remedial rehabilitation activities. Results The intervention group participants expressed improvement in physical health, ADL, psychological health, social relationship, and health in general as reflected by scores of the Perceived Benefit Questionnaire and informal feedback. Conclusion Although results are not significant in the generalization measures, it may be due to small effect size, small sample size, and short intervention period. Although not all of the hypotheses are supported, this report shows that Qigong (the Eight Section Brocades) is promising as an alternative intervention for elderly with chronic physical illness to improve their biopsychosocial health. More systematic evaluation with larger sample size and longer period of intervention is now underway in Hong Kong. Results will be reported once available. Copyright # 2003 John Wiley & Sons, Ltd.

A survey was conducted to assess the long term outcome of 60 elderly stroke survivors (mean age, 81.7 years). Of these patients, 48% died within one year of discharge and 79% of the mortality occurred in the first six months. Patients discharged to institutions after the initial stroke had a significantly higher risk of death in one year (relative risk=1.47) compared with those who were discharged home. For those who survived for a mean period of 18.6months, 72% (21/29) were institutionalised. This group had significantly worse functional status and mobility compared with those who were living at home. The caring of elderly stroke patients was considered a heavy burden for most carers at home or in institutions and the need for medical and social support was great.

The determination of limits and fits exists in nearly all engineering design works which involve mating parts. Their selection is a crucial process in achieving functional requirements and optimum cost of manufacture. This paper describes the development work of a prototype knowledge-based system (KBALF) capable of determining limits and fits. When relevant information for a given application is inputted, the system can help engineering designers through the whole process of determination of fits, ranging from recommendations of fits for assemblies, calculation of limits of sizes, to production of fit specification documents. By incorporating database of standard nominal sizes, the system also facilitates the process of standardization which in turn can reduce the cost of manufacture.

Delrin (DR) has been used in biomedical applications for more than 25 years. Because of durability concerns, it was replaced by the expensive Pyrolytic Carbon (PC) in numerous cardiac valves. However, the durability problem could be related to design rather than poor materials selection. Recent reports on brittle fracture of PC, leading to sudden deaths, have prompted a critical comparison between DR and PC in the St. Vincents Mechanical (SVM) heart valves. Three SVM-DR and SVM-PC valves were subjected to accelerated life cycle tests, and examined for wear at 400 million cycles. These results were compared to those of Björk-Shiley Delrin (BS-DR) valves. Wear in BS-DR valves in vivo for more than 17 years were also analyzed and compared. Using a linear (wear depth)-log (cycles) plot, wear rates in mm/log (million cycles) were obtained. The results showed that the wear rates for DR and PC in SVM valves are close. The double reduction in wear rate of the SVM-DR, compared to BS-DR, is probably due to the lower contact stresses of the SVM valves. SVM-DR in vivo should, therefore, have lower wear. The PC discs also showed edge chipping and hairline cracks. The authors conclude that the durability of DR can be improved by design and, since it is more impact resistant than PC, it is a safer, more inexpensive occluder material for cardiac valves.

A 54-year-old man underwent aortic valve replacement for syphilitic aortic regurgitation. Eight years later, he was admitted with sudden precordial discomfort and symptoms of superior vena caval obstruction. Ascending aortic dissection was diagnosed by echocardiography and computed tomography of the thorax. The patient succumbed rapidly after admission. Postmortem findings and histological features were compatible with syphilitic aortitis, without significant atherosclerosis. This case report adds to the sparse literature on aortic dissection complicating syphilitic aortitis, and illustrates that, at certain stages of the disease process, syphilitic aortitis can lead to such a degree of mechanical instability of the aortic wall as to predispose to dissection.

A prospective study on fact embolism showed that of ninety-five patients with a fractured shaft of the femur, seven (7 percent) demonstrated both pulmonary and cerebral disturbances, while there were profound disturbances in arterial PO2, hemoglobin level, pulse rate, and temperature in about 40 per cent of the patients. Using a modified Gurd test, a significant amount of fat was demonstrated in 5.7 per cent of the samples of venous blood and in 18.5 per cent of the samples of arterial blood. Language: en

The results of 269 patients who had undergone valvular operations during and 18-month period (January 1, 1980, to June 30, 1981) were analysed. One hundred and seventy-four patients referred for surgery had undergone routine cardiac catheterisation elsewhere, and these, together with four electively catheterised patients, constituted a group representing the conventional approach. Ninety-one patients were assessed only by clinical and non-invasive methods, including echocardiography, and were subjected to surgery without catheterisation. The two groups were comparable in their major clinical characteristics including age, sex ratio, functional class, previous history of closed mitral valvotomy, aetiology of valve lesions, and type of operative procedure performed. There was no discordance between operative finding and preoperative assessment, except in two patients of the catheterised group. Hospital mortality was acceptably low and was comparable between the two groups. Cardiac catheterisation is, thus, no longer necessary in the majority of patients undergoing surgery for valvular heart diseases.

One hundred and twenty three patients with tetralogy of Fallot over the age of thirteen years underwent total corrective surgery between July 1968 to December 1980 in the Hong Kong University, Cardiothoracic Centre at Grantham Hospital. The hospital mortality was 10.5 per cent. The number of late deaths was three. Eighty-three of the one hundred and six survivors were available for long-term follow-up. Significant residual ventricular septal defect was found in seven patients; four of these were successfully reoperated.

We reviewed the cases of 110 patients with paralytic scoliosis due to poliomyelitis who were operated on. In the lumbar region, anterior Dwyer instrumentation with posterior fusion gave excellent correction of scoliosis and pelvic obliquity. In the more rigid thoracic curves, combined anterior Dwyer instrumentation and posterior fusion gave better results than posterior fusion alone, but had more morbidity. Long c-shaped curves benefited more from a combined anterior Dwyer procedure at the apex of the curve and long posterior Harrington instrumentation. Traction was found to be of use only in rigid curves and in those larger than 80 degrees. With combined anterior and posterior fusion, there was a pseudarthrosis rate of 7 per cent in lumbar curves, none in thoracic curves, and 12.5 per cent in long c-shaped curves. The pseudarthrosis rate rose to more than 25 per cent in patients who had a posterior fusion alone.

With the use of conventional cardiopulmonary bypass and moderate hypothermia, primary intracardiac repair of large ventricular septal defects was performed in 30 children below the age of two years. All babies were falling to thrive and suffered from cardiac failure resistant to medical therapy, or had evidence of early pulmonary vascular disease. Two patients died after the operation, giving an operative mortality of 6.7%. Twenty-eight survivors have been followed for periods of one month to two and a half years. All are thriving and have normal or mildly enlarged hearts on their chest skiagrams. Primary intracardiac repair of large ventricular septal defects can be performed in infants and small children with a low operative risk when the standard cardiopulmonary bypass technique is being used.

A patient with malignant fibrous histiocytoma (MFH) of the mediastinum is reported. This is a very unusual site for MFH. Erosion of the thoracic aorta led to the formation of a false aneurysm, which ended fatally with rupture into the left lung. Clinical features of two other reported cases of MFH of the lung are also reviewed.

Two cases of malaria developing immediately after open-heart surgery are reported to illustrate that malaria is one of the rarer causes of postoperative pyrexia. The diagnosis can easily be missed, resulting in unnecessary morbidity and even mortality. It is important for cardiac surgeons to be aware of this possibility in malaria-free as well as malaria-endemic areas as patients or blood donors who come from or have recently visited an endemic area are potential victims or sources of the infection.

The results of a study of 239 resected solitary pulmonary nodules are presented; 66.5% of the resected nodules were malignant, and there were three patients with malignant coin lesions who were under 30 years of age. These findings confirm the generally accepted fact that most solitary pulmonary nodules must be resected if the presence of cancer is to be excluded. Transbronchial biopsy under biplane fluoroscopic guidance through a flexible bronchoscope may provide an effective alternative to early thoracotomy in the future, so that malignant nodules can be diagnosed before operation and patients with benign lesions are spared a thoracotomy.

A 42-year-old man presented with haemoptysis of undetermined cause for five months despite thorough investigation. Exploratory thoracotomy showed there had been "silent" penetration by a chicken bone through oesophagus into the lung. A retrospective review showed that the foreign body could be seen in only four out of 54 chest roentgenograms taken.

Two cases of asymptomatic lipothymoma, discovered on "routine" roentgenograms of the chest, are presented. Thirty well-documented reports of this tumor in the English literature are reviewed. The pertinent points concerning this rare clinicopathological entity are summarized and discussed.

Between July 1968 and June 1977, in the University of Hong Kong Department of Surgery, 1,083 patients underwent operations via a median sternotomy using a Y incision. Of these patients, 1,070 had open heart surgery, eight had total thymectomy and in five patients pericardectomy was carried out. The overall wound complication rate was 2.31%, with a wound infection rate of 1.24%. The main advantage of a Y incision is that it leaves a better cosmetic appearance than the usual vertical incision because the upper end of the scar is at a much lower level. The incidence of subcutaneous haematoma and subsequent wound infection is much lower with the Y incision, whereas the T incision is associated with a high rate of both these complications due to the large upper flap that one has to create and mobilize to expose the suprasternal area. While using the Y incision, one only requires a small V-shaped upper flap to obtain access to the suprasternal space.

Sixty-four cases of coexistent bronchogenic carcinoma and active pulmonary tuberculosis were diagnosed between 1969 and 1976. The majority were male chronic cigarette smokers in their fifth and sixth decades. Human bacilli were isolated in 48 patients (88.9 percent) and atypical bacilli in six patients (11.1 percent). All of the atypical bacilli and 8.3 percent of the human bacilli were found to be resistant to the first line antituberculous drugs. All patients, except two who died following resection, were given a course of antituberculous drugs with 93.8 percent successful sputum conversion. Uncontrolled or disseminated tuberculous infection was not observed. Forty-five patients (70.3 percent) underwent pulmonary resection. Median survival time of those who had curative resection was 14.3 months with a 5 year survival rate of 13.2 percent. Median survival times of those treated by palliative resection plus anticancer chemotherapy and by anticancer chemotherapy alone were 8.3 months and 11.1 months, respectively. None of these patients survived more than 30 months. It appears that, clinically, each disease runs its own course with little effect on the other.

In a prospective study of deep-vein thrombosis following hip surgery for fractures of the proximal femur, 45 Hong Kong Chinese patients were examined by bilateral functional ascending phlebography 7 to 28 days postfracture and 5 to 15 days post-surgery. In 14 patients, the phlebography was repeated 10 to 32 days later. The patients were followed for 27 to 32 months. The phlebographic pattern of the venous thrombi were analyzed, and the clinical course of the patients was presented. Despite the fact that the overall incidence of deep-vein thrombosis in this group of Chinese patients was similar to that reported in the West, clinical pulmonary embolism was not observed. The study suggested a difference in the distribution, pattern and probably the natural history of the venous thrombi among the Chinese when compared with the Western series.

The effects of rheumatic mitral valvular disease and mitral valve replacement on the growth and development of 37 Southern Chinese children were studied. The stature and body weight were measured before and after operation. All the patients had their skeletal maturity and cortical bone growth assessed after operation, but only 10 patients were similarly assessed before operation. At the time of operation the stature and body weight of all patients were generally retarded. The surgery which corrected the haemodynamic abnormality resulted in increases in the growth rates in stature and body weight but there was no evidence of a catch-up growth with subsequent return to normal dimensions. The patients who are skeletally immature had retarded bone ages and impaired growth of cortical bone. The general trend, though less marked, also showed a reduction in cortical bone in the skeletally mature patients. Surgery appears, at least partially, to alleviate the adverse effects of the disease on the growth and development of patients.

There has been no report of malignant mesothelioma or asbestosis in Hong Kong despite the rapid growth of industry in the past few decades. Three patients with malignant pleural mesothelioma and one patient with asbestosis and small cell carcinoma of the lung are reported. All four patients were Chinese in Hong Kong and had a history of occupational exposure to asbestos. Although there is no mining of asbestos in Hong Kong, her rapid industrialization in the past few decades has led to a large population of asbestos-exposed workers in industry. The average annual consumption of crude asbestos (import minus re-export) has grown ten-fold in the past decade to 1.090 tonnes in 1978-79, and the number of workers handling asbestos products was estimated to be 20.000 in 1979. The problem of asbestos related diseases has however been little considered and further epidemiologic studies are warranted.

A 37 year old Chinese man presenting with features of chest infection was diagnosed as having severe aortic regurgitation. Cross sectional echocardiography showed an intact right coronary sinus of Valsalva aneurysm, which protruded into the left ventricle. The changes in appearance of the aneurysm during the cardiac cycle were recorded by cross sectional echocardiography. The opening of the aneurysm was successfully closed and the aortic valve replaced with a mechanical prosthesis.

In a prospective, randomized, parallel study, two regimens of platelet-suppressant therapy (PST)--dipyridamole-aspirin and pentoxifylline-aspirin--were compared with standard oral anticoagulation with warfarin in the prevention of prosthetic heart valve thromboembolism. In the entire group of 254 patients followed for 395.6 patient-years, the thromboembolic rate was significantly less in the warfarin group (warfarin vs dipyridamole-aspirin, p less than .005; warfarin vs pentoxifylline-aspirin, p less than .05). Subgroup analysis disclosed that, in patients with isolated mitral valve replacement, warfarin was superior to both of the PSTs with respect to the prevention of thromboembolism (warfarin vs dipyridamole-aspirin, p = .005; warfarin vs pentoxifylline-aspirin, p less than .05). Furthermore, a significant number of our patients could not tolerate the antiplatelet agents. However, in the rare situation in which repeated significant bleeding occurs despite careful adjustment of the dosage of warfarin, PST may be an acceptable alternate method of thromboembolism prophylaxis.

A 78 year old man underwent aortic valve replacement because of acute aortic regurgitation and intractable heart failure. At operation the intact commissure between the left and right coronary cusps of a grossly normal aortic valve was found to have separated from the aortic wall. Histopathological examination of the surgical specimen showed that the site of separation was an atheromatous plaque. This is believed to be the first report of this feature., link_to_OA_fulltext

In two patients, several chordae tendineae of the mural leaflet were preserved during mitral valve replacement. Hemorrhagic necrosis and spontaneous rupture of the preserved posterior papillary muscle led to disc entrapment and the death of both patients.