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Studies in cats have shown that, in addition to respiratory neuron groups in the dorsomedial (DRG) and ventrolateral (VRG) medulla, neural structures in the most ventral medullary regions are important for the maintenance of respiratory rhythm. The purpose of this study was to determine whether a similar superficially located ventral region was present in the dog and to assess the role of each of the other regions in the canine medulla important in the control of breathing, in 20 anesthetized, vagotomized, and artificially ventilated dogs, a cryoprobe was used to cool selected regions of the medulla to 15-20 degrees C. Respiratory output was determined from phrenic nerve or diaphragm electrical activity. Cooling in or near the nucleus of the solitary tract altered timing and produced little change in the amplitude or rate of rise of inspiratory activity; lengthening of inspiratory time was the most common timing effect observed. Cooling in ventrolateral regions affected the amplitude and rate of rise of respiratory activity. Depression of neural tidal volume and apnea could be produced by unilateral cooling in two ventrolateral regions: 1) near the nucleus ambiguus and nucleus para-ambiguus and 2) just beneath the ventral medullary surface. These findings indicate that in the dog dorsomedial neural structures influence respiratory timing, whereas more ventral structures are important to respiratory drive.

Over twenty six percent of the bridges in the United States are structurally deficient or functionally obsolete. Corrosion of steel used in structures like bridges and buildings is a problem that has gained increased interest and focused concern. Steel is often the metal that is preferred for use in such applications due to a synergism of ease of availability, acceptable mechanical properties and cost effectiveness. Through the years, titanium has grown in strength, stature and significance to be recognized as an emerging high performance metal that is both stronger and lighter than steel. A distinctive property of titanium and its alloys is its non-corrosive nature. However, a major drawback in the selection and use of pure titanium or its alloy counterpart is the prohibitively high cost. Therefore, it may be possible to combine steel and pure titanium and/or its alloy in structures by restricting steel for bulk of the structure and selectively using titanium and its alloys for the critical but low volume elements, such as, gusset plates and bearings. A hybrid use of titanium in conjunction with steel for structural members will result in better performance while concurrently proving to be both cost-effective and economically affordable. The synergistic use of structural steel and titanium in close proximity with each other could result in accelerated corrosion of steel in the immediate vicinity of titanium. The corrosion performance of titanium plates coupled with steel members is presented. A few viable strategies for minimizing galvanic coupling effects between steel and titanium are discussed. Corrosion experiments were conducted to measure the severity of corrosion when titanium and steel form a galvanic couple, and copper and steel was a comparative system. The study revealed that adequate precautions are needed to minimize localized corrosion when titanium gusset plates are coupled with structural steel members.