The Formal Language and Design Principles of Autonomous DNA Walker Circuits

Simple computation can be performed using the interactions between single-stranded molecules of DNA. These interactions are typically toehold-mediated strand displacement reactions in a well-mixed solution. We demonstrate that a DNA circuit with tethered reactants is a distributed system and show how it can be described as a stochastic Petri net. The system can be verified by mapping the Petri net onto a continuous-time Markov chain, which can also be used to find an optimal design for the circuit. This theoretical machinery can be applied to create software that automatically designs a DNA circuit, linking an abstract propositional formula to a physical DNA computation system that is capable of evaluating it. We conclude by introducing example mechanisms that can implement such circuits experimentally and discuss their individual strengths and weaknesses.

The role of the individual administrator in famine relief: Three case studies

A series of hypotheses on the role of the individual administrator in famine relief are proposed and three are examined with respect to case studies of famines in India (1896 and 1906-1907), Uganda (1908) and Lombok (1940). While the evidence is not conclusive, the focus upon the role of the individual administrator offers additional insights into the compexities of official response to famines.

Bronchoscopy in the critically ill surgical patient

Sixty-seven bronchoscopic examinations were performed in a busy surgical intensive care unit on 51 patients, and the techniques, morbidity, and outcome were prospectively analyzed to assess the efficacy and safety of the procedure in this particular patient population. General surgical trauma, cardiothoracic, and orthopedic patients were included. Fifty-three (79%) procedures were performed with the flexible instrument, while 14 patients (21%) underwent rigid endoscopy. Forty-six patients were being mechanically ventilated; 30 had endotracheal tubes, and 16 had tracheostomies. Suspected lobar collapse (60%), persistent pulmonary infiltrates (3%), suspected aspiration (21%), and suspicion of airway trauma (12%) were the primary clinical indications for bronchoscopy. No deaths occurred. Complications were seen in 16 per cent of the procedures and 17 per cent of the patients. There were arrhythmias (other than sinus tachycardia) in seven procedures (11%) and one episode each of hypertension, self-limited endobronchial bleeding, mediastinal emphysema, and increased intracranial pressure. Significant improvement was demonstrated for patients with lobar collapse but not for those with mild atelectasis or pulmonary infiltrates on radiographs taken within 24 hours. Overall, 39 patients (58%) improved radiographically, while 38 patients (42%) did not. Differences in arterial PO2 measured before and after bronchoscopy between groups ventilated with an FiO2 of 1.0, and those who were not did not achieve statistical significance (P less than 0.05).

Subxiphoid pericardiotomy. A safe, accurate, diagnostic and therapeutic approach to pericardial and intrapericardial disease

The records of 36 patients who underwent subxiphoid pericardiotomy were reviewed to determine the safety, accuracy, and utility of the procedure. No deaths were attributed to the operation, and complications were minimal. Most operations were performed under local anesthesia. Findings at operation accurately defined which patients required further surgery and which did not. Although clinical, radiographic, and physical findings are inaccurate in determining the nature and extent of pericardial and intrapericardial pathology, a definitive diagnosis was obtained in all diagnostic procedures. Only one patient needed a second operation, attesting to the effectiveness of subxiphoid drainage as a therapeutic modality.

Purulent mediastinal abscess secondary to Ludwig's angina

A case of Ludwig's angina dissected along deep cervical fascial planes into the mediastinum caused a virulent mediastinitis and abscess. Computed tomography precisely delineated the extent of the infection. Incomplete débridement resulted in a residual abscess and persistent systemic sepsis that culminated in the patient's death. Aggressive antibiotic treatment of the orofacial cellulitis along with complete mediastinal drainage are recommended for optimal outcome.

Use of the rhomboid major muscle flap for esophageal repair

A 16-year-old boy sustained vehicular blunt trauma with delayed esophageal rupture that resulted in empyema and an esophagopleurocutaneous fistula. Diverting esophagostomy, gastrotomy, and transpyloric jejunostomy were performed, and these procedures permitted satisfactory nutritional support of the patient. Staged direct closure of the esophagus buttressed by a rhomboid muscle flap preserved normal esophageal function. Both clinical application and cadaver dissections have demonstrated that the rhomboid flap has an excellent blood supply and that it can be used to repair lesions on either side in the upper half of the esophagus. Because this flap is extrathoracic, it is not usually distorted by intrathoracic sepsis or previous thoracic incisions. The rhomboid major muscle flap is an excellent alternative to conventional autogenous grafts for esophageal repair.

Intra-aortic balloon counterpulsation for cardiogenic shock from cardiac contusion

Two patients who sustained cardiac contusions secondary to blunt chest trauma developed refractory cardiogenic shock. Use of intra-aortic balloon counterpulsation improved circulatory dynamics in each case and one patient survived. Requirements for inotropic agents were diminished or eliminated, cardiac output was increased, acidosis was reversed, and the electrocardiogram reverted to normal. Although balloon counterpulsation is most effectively employed in patients with ischemic cardiac deficits, its early application coupled with appropriate pharmacologic treatment is also effective in raising low cardiac output that results from myocardial trauma.

Traumatic injury of the proximal superior mesenteric artery

Injuries of the proximal superior mesenteric artery (SMA) are relatively uncommon, but extremely perplexing lesions. Fifteen consecutive patients with this injury, 13 injuries from gunshot wounds and two injuries from blunt trauma, have been treated. Associated lesions and massive blood loss were common, averaging 3.6 injuries and 4800 ml per patient, respectively. Methods of SMA repair include lateral arteriorrhaphy (11 patients), primary reanastomosis (3 patients), and saphenous vein grafts (1 patient). Two of three patients whose injuries included segmental loss of the SMA that required a primary end-to-end anastomosis suffered subsequent thrombosis. Second-look operations were performed in five patients with two of these requiring a further reconstructive procedure. The only late death occurred in a patient with a severe head injury and a failure of his SMA repair, which potentially could have been prevented by a second-look procedure. There were five deaths (33%), with four occurring from acute hemorrhages and one late death occurring following intestinal necrosis and sepsis. Malabsorption or other late intestinal complications did not occur. Our experience 1) supports the concept that proximal SMA lesions must be repaired, 2) suggests that primary anastomosis to repair arterial defects is associated with a high failure rate, and 3) demonstrates that the second-look operation is a useful adjunct in improving survival in these patients.