Comparing Regime-Switching Models In Time Series: Logistic Mixtures vs. Markov Switching

The purpose of this thesis is to review several related regime-switching time series models. Specifically, we use simulated data to compare models where the unobserved state vector follows a Markov process against an independent logistic mixture process. We apply these techniques to crude oil and heating oil futures prices using several explanatory variables to estimate the unobserved regimes. We find that crude oil is characterized by regime switching, where prices alternate between a high volatility state with low returns and significant mean reversion and a low volatility state with positive returns and some trending. The spread between one-month and three-month futures prices is an important determinant in the dynamics of crude oil prices

Percutaneous tracheostomy-beware of the thyroidea-ima artery

Percutaneous tracheostomy is a minimally invasive operation performed in patients, in order to provide an air passage through the windpipe. A rare cause of severe bleeding during such operation is the injury of the thyroidea-ima artery. This case report presents a patient with hemorrhage after thyroidea-ima injury during percutaneous dilatational tracheostomy. Surgeons should always be aware of such anatomic variation, in order to prevent urgent sternotomy

Galactorrhea, mastodynia and gynecomastia as the first manifestation of lung adenocarcinoma. A case report

Gynecomastia with mastodynia and galactorrhea as a paraneoplastic syndrome due to lung cancer with complete response after surgical excision is rare. A 62-year-old Caucasian male presented with mastodynia, galactorrhea and right breast enlargement. Chest x-ray revealed a left upper lobe tumor. The patient had high levels of serum beta-human chorionic gonadotropin (b-HCG) and prolactine. Complete staging was negative for metastases. A typical left upper lobectomy with radical mediastinal lymph node dissection was performed. Pathology report was consistent with a poorly differentiated adenocarcinoma (T2N1M0). Immunohistochemically, multinucleate cells and occasional mononucleate tumor cells showed positivity for human chorionic gonadotropin. The patient received adjuvant chemotherapy with cisplatin - navelbine. One year later physical examination showed regression of both gynecomastia and mastodynia and there was no nipple discharge, while he is free from local or distant metastatic disease and the b-HCG level is normal (1,59 mIU/ml). This case represents a very rare, first manifestation of lung cancer. Galactorrhea, mastodynia and gynecomastia were the initial symptoms, which totally resolved following the successful surgical resection and adjuvant chemotherapy. In this case, prolactin and b-HCG are useful biomarkers during follow up for checking local or distal recurrence of the disease

Successful surgical treatment of a complicated esophageal perforation, by use of primary closure and lung parenchyma reinforcement

Esophageal perforation (EP) is a medical condition which demands urgent confrontation with significant complications. The cause of the perforation may be common, spontaneous or iatrogenic, with conservative or surgical therapeutic strategy, which is needed in the majority of incidents, depending on the characteristics of the lesion. We report a case of a 68-year-old man, with the existence of an ulcerative lesion 31 cm approximately from the dental barrier, and a coexistent stenosis, diagnosed through esophagogastroduodenoscopy, which evolved to an extensive purulent necrotic mediastinitis, diagnosed through a thorax CT scan after the patient began to complain of asphyxiation during eating. A right posterolateral thoracotomy was performed along with intensive wide spectrum antibiotic therapy. Primary closure of the perforation as well as pulmonary tenting was used with satisfactory results. There was no evidence of leakage after a 12-month "follow-up" period. The early diagnosis of an EP combined with immediate surgical procedure and frequent "follow-up" of the patient, eliminate the risks for the patient's life and ensure a satisfactory outcome