Simulation: A Survey with Research Suggestions

Simulation is one of the most powerful analysis tools available to those responsible for the design and/or operation of complex processes or systems. It is heavily based upon computer science, mathematics, probability theory and statistics; yet the process of simulation modeling and experimentation remains very much an intuitive art. This paper attempts to survey selected aspects and point out areas needing additional research. Among the topics discussed are: random variate generation, programming languages, starting conditions, sample size, variance reduction, design of experiments and validation.     

Morse-code-controlled computer aid for the nonvocal quadriplegic

A computer-based communications system was established for a quadriplegic patient who suffered a brainstem infarction that left him with normal intelligence, but without speech and without functional motor control except for the thumb of his right hand. An arm brace was developed to support the hand and thumb so it could control two switches that generated Morse code signals. An interface was also devised to translate Morse code into ASCII characters to access a personal computer. Additional codes were added to represent keyboard control functions. This device allows the patient to communicate with others and control, to some extent, his environment.     

The influence of the lymph node on the protein concentration of efferent lymph leaving the node

1. Experiments have been performed in sheep to determine the contribution of lymph formed within a lymph node to the total protein output in lymph leaving the node. 2. The lymphatic duct leaving the popliteal lymph node was cannulated and the protein and lymphocyte output in efferent lymph determined. The afferent lymph flow to the popliteal node was then diverted and lymph formed only within the lymph node collected from the efferent cannula. It appeared from the results that the popliteal lymph node forms lymph at the rate of approximately 1 ml. per hour and may contribute 30-50% of the protein output observed in efferent lymph. 3. The importance of lymph formation within the lymph node varied between nodes found in different regions of the body. This was due in part to the different protein concentrations in the afferent lymph to the different nodes. 4. A positive correlation was found between the protein and lymphocyte concentrations in efferent lymph from the popliteal lymph node in seven out of eleven sheep and in lymph formed within the popliteal lymph node in two out of three sheep. It is suggested that this relationship may be due to an increased transfer of plasma proteins through the post-capillary venules in the lymph node accompanying the continual traffic of lymphocytes across the wall of these vessels. The results indicated that the protein transfer across the post-capillary venules was not an indiscriminate transfer of plasma per se but a selective transport from the blood plasma compartment based on molecular size.     

Seat-belt legislation and risk homeostasis: Further analysis of the British data

It has been suggested that seat-belt legislation may result in drivers' feeling overprotected and their consequent riskier driving may lead to more injuries to other road users (the risk homeostasis or compensation theory). We have examined data in Britain before and after legislation made seat-belt use compulsory for front-seat occupants of specified vehicles. The relative numbers of injuries to cyclists and pedestrians in collisions with vehicles requiring and not requiring seat-belt use were compared, using a loglinear analysis taking into account possible confounding variables. It was not possible directly to incorporate vehicle distance travelled for the two categories of vehicle. However, a simple adjustment for differential vehicle use accounted for most of an apparent effect. The revised odds ratio (for mandated seat-belt use vehicles versus nonmandated, post- versus prelegislation) was 1.04 for cyclists and 1.06 for pedestrians, showing minimal, if any, evidence for the theory.     

In vitro antibacterial activity and susceptibility of cefsulodin, an antipseudomonal cephalosporin, to beta-lactamases

Cefsulodin sodium (SCE-129, CGP-7174/E), active in minimum inhibitory concentrations (MICs) of 0.5 to 64 microgram/ml, was about 16- to 32-fold more active than carbenicillin against Psuedomonas aeruginosa. It was also active against P. diminuta, P. maltophilia, P. paucimobilis, and P. pseudoalcaligenes (MICs of 1 to 32 microgram/ml) but not against other species of Pseudomonas or other gram-negative bacteria. Except with highly carbenicillin-resistant isolates, MICs of cefsulodin for P. aeruginosa were little affected by an increase in the inoculum. With a small inoculum, minimum bactericidal concentrations (MBCs) were the same as or twice the MIC, but increasing the inoculum had a greater effect on the MBC than on the MIC. Cefsulodin was not hydrolyzed by the beta-lactamase induced in P. aeruginosa by growth in the presence of benzylpenicillin and was a poor substrate for beta-lactamases from Enterobacter cloacae and Proteus morganii. However, it was hydrolyzed, albeit slowly, by the beta-lactamase produced by most of our highly carbenicillin-resistant isolates of P. aeruginosa and by TEM-type beta-lactamases.     

Operation Research Methodologies in Industrial Engineering: A Survey

This study presents the results of a survey taken among members of the Operations Research Division of the American Institute of Industrial Engineers as to perceived utility and familiarity with twelve methodologies commonly used in Industrial Engineering practice. A modification to the method of majority rule for weighting the opinions of respondents, based upon their degree of familiarity or expertise, is also presented.