Optimal control and performance analysis of an M-X/M/1 queue with batches of negative customers

We consider a Markov decision process for an MX/M/1 queue that is controlled by batches of negative customers. More specifically, we derive conditions that imply threshold-type optimal policies, under either the total discounted cost criterion or the average cost criterion. The performance analysis of the model when it operates under a given threshold-type policy is also studied. We prove a stability condition and a complete stochastic comparison characterization for models operating under different thresholds. Exact and asymptotic results concerning the computation of the stationary distribution of the model are also derived

Bilateral spontaneous hemotympanum: Case report

BACKGROUND: The most common causes of hemotympanum are therapeutic nasal packing, epistaxis, blood disorders and blunt trauma to the head. Hemotympanum is characterized as idiopathic, when it is detected in the presence of chronic otitis media. A rare case of spontaneous bilateral hemotympanum in a patient treated with anticoagulants is presented herein. CASE PRESENTATION: A 72-year-old male presented with acute deterioration of hearing. In the patient's medical history aortic valve replacement 1 year before presentation was reported. Since then he had been administered regularly coumarinic anticoagulants, with INR levels maintained between 3.4 and 4.0. Otoscopy revealed the presence of bilateral hemotympanum. The audiogram showed symmetrical moderately severe mixed hearing loss bilaterally, with the conductive component predominating. Tympanograms were flat bilaterally with absent acoustic reflexes. A computerized tomography scan showed the presence of fluid in the mastoid and middle ear bilaterally. Treatment was conservative and consisted of a 10-day course of antibiotics, anticongestants and temporary interruption of the anticoagulant therapy. After 3 weeks, normal tympanic membranes were found and hearing had returned to previous levels. CONCLUSION: Anticoagulant intake should be included in the differential diagnosis of hemotympanum, because its detection and appropriate treatment may lead to resolution of the disorder