Comprehensive analysis of results of surgical treatment of oral tongue carcinoma in Hong Kong

OBJECTIVE: To evaluate the results of primary surgical treatment of carcinoma of oral tongue in Hong Kong. METHODS: Patients who had undergone primary surgical treatment of oral tongue carcinoma in Queen Mary Hospital were reviewed. RESULTS: There were 112 patients in this study. The first sites of tumor recurrence were 10 (9%) local, 25 (22%) nodal, 3 (3%) locoregional, 5 (5%) distant, 1 (1%) local and distant, 3 (3%) nodal and distant, and 1 (1%) neck extranodal site. Of the 63 T1-2 N0 M0 patients, the regional recurrence rate was 9% for elective neck dissection compared with 47% for "watchful waiting" (Chi-square test, P = 0.0008). The regional recurrence related mortality was 3% for elective neck dissection compared with 23% for "watchful waiting" (Fisher's test, P = 0.02). The 5-year actuarial survival rate was 86% for elective neck dissection compared with 55% for "watchful waiting" (Wilcoxon, P = 0.01). CONCLUSIONS: Local and regional recurrences were the main sites of treatment failure. Elective neck dissection has significant benefits in the reduction of regional failure and improvement of survival. Elective selective I-III neck dissection have to be considered in patients with stage I and stage II oral tongue carcinoma.     

Cost-benefit analysis of the use of TBT: the case for a treatment approach

The current climate of hostility towards the use of tributyltin (TBT) as an active ingredient in ship anti-fouling paint appears to be based on a very biased assessment of its environmental impact. While many national and international regulatory agencies are moving towards further restriction, and a complete ban is under active discussion, a number of factors appear to have been ignored. The economic impact of a ban on TBT when no adequate substitute exists could be substantial. Environmentally, consequences would include a substantial increase in the consumption of fossil fuel, with corresponding increases in carbon dioxide and sulphur dioxide emissions; the construction of more vessels; the transfer of ship-building, ship-repairing and ship-breaking activities from well-regulated to unregulated or under-regulated areas in the developing world; and a shift from sea transport to less environmentally acceptable forms of transport. Experience in Europe and other parts of the developed world shows that existing restrictions, where they are properly enforced, are probably adequate to alleviate the environmental damage associated with TBT. Some existing legislation acts to inhibit the search for effective substitutes. The environmental benefits of TBT have been ignored. Little thought has been given to a technical, rather than a legislative solution to controlling TBT inputs to the environment. A method is described for treating TBT-contaminated wastewaters, which has been successfully tested in prototype at full scale. Legislative measures against TBT will do nothing to address the problem of the existing backlog of contaminated material, nor even to permit the IMO proposal for the removal of TBT from all ships by 2008 to be successfully concluded in an environmentally safe manner, since no provision has been made for the disposal of the existing TBT; most probably it will be dumped in environmentally sensitive, unregulated areas in the developing world.     

Biophysical processes and bioregional planning: The Niagara Escarpment of southern Ontario, Canada

The Niagara Escarpment is the dominant landscape feature of Southern Ontario and has been designated a UNESCO World Biosphere Reserve. As with many such natural features, the resource planning and management strategies developed tend to be based upon the present-day situation rather than upon a recognition of the changing and evolving nature of the feature. To develop strategies incorporating change demands that a knowledge be gained of the processes operating in those components of the ecosystems in which measurable activity will take place within a planning framework; that is a timescale of several decades. In this particular case, the context is natural resource planning for the scarp face itself. The critical system elements are those related to earth surface processes, forest ecosystem dynamics, and in particular, their interrelationships. Different planning objectives require information at differing spatial scales. Yet these objectives must be related, whether they are local site-specific issues, or are related to the maintenance of the biodiversity of the whole 725 km of the Escarpment. One way to achieve these goals is to establish a hierarchical system of spatially nested land units. These units, however, must be based on the underlying biophysical processes responsible for the dynamics in any one of these spatially determined frameworks. In this case, the underlying biophysical processes relating to geomorphology and forest ecosystem dynamics are found to be influenced by one of three dominant slope forms. The recurrence of these slope forms throughout the Escarpment then permits 9 distinct regional land units to be identified. Within these units, site-specific analysis examines earth surface/forest interactions and change. Subsequently, from these site specific analyses data are accumulated to develop a more general model of earth surface/forest ecosystem interaction for the Escarpment as a whole.     

The modified dynamic model of a riser type fluid catalytic cracking unit

The dynamic model developed by Ali and Rohani (1997) to describe the transient behavior of a fluid catalytic cracking (FCC) unit is modified (i) to incorporate the effect of volumetric expansion of the feed and product gases flowing in the riser reactor (ii) to consider the enhancement of mass and heat transfer coefficients due to high turbulence in the regenerator and (iii) to model the reactor and stripper as a continuous stirred tank. The modified model is validated using steady-state plant data from an industrial unit (Consumer's Co-operative Refineries Ltd., Regina, SK) and the results are found to be in good agreement.     

Strategies for mitigating an influenza pandemic with pre-pandemic H5N1 vaccines

The recent worldwide spread of the swine-origin H1N1 2009 influenza outbreak has resulted in its designation as a pandemic by the World Health Organization. While it appears to result in mild symptoms, concern still exists that a more severe influenza pandemic with a high case fatality ratio might arise by reassortment or mutation of the currently circulating avian influenza (H5N1) virus. Given that recently developed candidate pre-pandemic H5N1 vaccines have shown potential for cross-strain protection, we investigated alternative vaccination strategies that exploit such vaccines using an agent-based simulation model of an actual community of approximately 30 000 people in a developed country. Assuming that a two-dose vaccination regimen would be required, we examined three vaccination strategies: pre-emptive, with vaccination applied prior to emergence of human-transmissible H5N1 influenza; reactive, where vaccination was initiated immediately after the first cases in the community were diagnosed; and a ‘split’ strategy where the first dose was administered pre-emptively during the pre-pandemic phase, with the second dose administered reactively. We showed that by effectively moving the delay between first and second doses into the pre-pandemic period, the split vaccination strategy achieved a substantially better attack rate reduction than the reactive strategy. Our results for an influenza strain with a reproduction number of 1.5 suggest reactive vaccination strategies that may be applicable to the current H1N1 2009 pandemic.     

Pulmonary embolism: predicting disease severity

Pulmonary embolism (PE) is the most common cause of acute pulmonary hypertension, yet it is commonly undiagnosed, with risk of death if not recognized promptly and managed accordingly. Patients typically present with hypoxemia and hypomania, although the presentation varies greatly, being confounded by co-morbidities such as pre-existing cardio-respiratory disease. Previous studies have demonstrated variable patient outcomes in spite of similar extent and distribution of pulmonary vascular occlusion, but the path physiological determinants of outcome remain unclear. Computational models enable exact control over many of the compounding factors leading to functional outcomes and therefore provide a useful tool to understand and assess these mechanisms. We review the current state of pulmonary blood flow models. We present a pilot study within 10 patients presenting with acute PE, where patient-derived vascular occlusions are imposed onto an existing model of the pulmonary circulation enabling predictions of resultant haemodynamic after embolus occlusion. Results show that mechanical obstruction alone is not sufficient to cause pulmonary arterial hypertension, even when up to 65 per cent of lung tissue is occluded. Blood flow is found to preferentially redistribute to the gravitationally non-dependent regions. The presence of an additional downstream occlusion is found to significantly increase pressures.     

Effective use of nisin to control Bacillus and Clostridium spoilage of a pasteurized mashed potato product

Heat-resistant spore-forming bacteria such as Bacillus and Clostridium can survive and grow in cooked potato products. This situation represents both a public health problem and an economic problem. The natural food preservative nisin is used in heat-treated foods to prevent the growth of such bacteria. A cocktail of Clostridium sporogenes and Clostridium tyrobutyricum spores was inoculated into cooked mashed potatoes, which were vacuum packed, pasteurized, and incubated at 8 and 25 degrees C. The shelf life of the mashed potatoes at 25 degrees C was extended by at least 58 days with the addition 6.25 microg of nisin per g. At 8 degrees C, in control samples not containing nisin, the natural contaminant Bacillus grew, but the inoculated Clostridium strains did not until the temperature was raised to 20 degrees C after 39 days. No bacterial growth occurred in nisin-containing samples. The shelf life of the mashed potatoes was extended by at least 30 days with 6.25 microg of nisin per g. In trials involving a cocktail of Bacillus cereus and Bacillus subtilis strains, 6.25 microg of nisin per g extended the shelf life of mashed potato samples that were not vacuum packed by at least 27 days at 8 degrees C. At 25 degrees C, 25 microg of nisin per g extended shelf life by a similar period. Shelf life extension was also observed at lower nisin levels. Microbiological analysis of the mashed potato ingredients showed that a high spore level was associated with the onion powder. It is emphasized that the preservative and the ingredients must be well mixed to ensure good nisin efficacy. Nisin remained at effective levels after pasteurization, and good retention was observed throughout the shelf life of the mashed potatoes.