Bit-Error-Rate-Minimizing Channel Shortening Using Post-FEQ Diversity Combining and a Genetic Algorithm

In advanced wireline or wireless communication systems, i.e., DSL, IEEE 802.11a/g, HIPERLAN/2, etc., a cyclic prefix which is proportional to the channel impulse response is needed to append a multicarrier modulation (MCM) frame for operating the MCM accurately. This prefix is used to combat inter symbol interference (ISI). In some cases, the channel impulse response can be longer than the cyclic prefix (CP). One of the most useful techniques to mitigate this problem is reuse of a Channel Shortening Equalizer (CSE) as a linear preprocessor before the MCM receiver in order to shorten the effective channel length. Channel shortening filter design is a widely examined topic in the literature. Most channel shortening equalizer proposals depend on perfect channel state information (CSI). However, this information may not be available in all situations. In cases where channel state information is not needed, blind adaptive equalization techniques are appropriate. In wireline communication systems (such as DMT), the CSE design is based on maximizing the bit rate, but in wireless systems (OFDM), there is a fixed bit loading algorithm, and the performance metric is Bit Error Rate (BER) minimization. In this work, a CSE is developed for multicarrier and single-carrier cyclic prefixed (SCCP) systems which attempts to minimize the BER. To minimize the BER, a Genetic Algorithm (GA), which is an optimization method based on the principles of natural selection and genetics, is used. If the CSI is shorter than the CP, the equalization can be done by a frequency domain equalizer (FEQ), which is a bank of complex scalars. However, in the literature the adaptive FEQ design has not been well examined. The second phase of this thesis focuses on different types of algorithms for adapting the FEQ and modifying the FEQ architecture to obtain a lower BER. Simulation results show that this modified architecture yields a 20 dB improvement in BER

Carotid Body Tumors and Our Surgical Approaches

Glomus tumors known as paragangliomas are neoplasms arising from the neural crest. They are named according to the place they originate from. Tumors originating from the carotid body at the carotid bifurcation are called Carotid Body Tumors (CBT). Surgical intervention is planned according to the Shamblin classification. 17 patients were operated after being diagnosed with CBT in our clinic between February 2007 and June 2010. 12 (70.5%) of the patients were male, and 5 (29.4%) of the patients were female. The average age was 42 (ages ranging between 32 and 47). Nine of the patients were diagnosed and treated with Shamblin type I tumor, seven of the patients with type II and one patient with type III. Only one patient had bilateral carotid tumor. In all patients with Shamblin type I and II, blunt dissection of the tumor was conducted smoothly by means of thermal cautery in the subadventitial plane. The patient with Shamblin type III had tumor invasion in the carotid artery and adjacent tissues were in an adherent state. Therefore mass resection was carried out by resecting 2 cm of the distal portion of the common carotid artery and 3 cm of the proximal portion of the internal carotid artery. 6 mm of synthetic polytetrafluoroethylene graft was interpositioned between the common carotid artery and the internal carotid artery. External carotid artery was anastomosed to this graft in an end-to-end fashion. The patient developed vocal cord paralysis postoperatively on the lesion side. The patient who underwent bilateral tumor excision developed Baroreflex Failure Syndrome. In the two patients thrombus developed in the internal carotid artery in the early postoperative period. These patients underwent thrombectomy and developed hemiplegia on the lesion side. One of them died on the seventh post-operative day while in follow-up in the intensive care unit. Surgical resection is the recommended treatment for carotid body tumors. Shamblin I and II type tumors' dimensions and pathological characteristics allow dissection. However Shamblin III tumors may require carotid artery resection and reconstruction due to tissue invasion. The possibility of post-operative cranial nerve paralysis and arterial thrombosis should be taken into account

Severe Destruction of the Upper Respiratory Structures After Brief Exposure to a Dieffenbachia Plant

Dieffenbachia is a common domestic plant. Oral contact with the plant generally causes slight effects, but when chewed it may result in painful oropharyngeal edema. Even though the mechanism through which this plant causes toxicity is not known, calcium oxalate crystals (rhaphides) and protease in the idioblast of the plant are considered to be the causes. Our aim was to show the lethal effects of a common domestic plant named Dieffenbachia

Huge Internal Carotid Artery Aneurysm Presenting as Tonsillar Asymmetry

Aneurysms of the extracranial portion of the carotid artery are extremely rare. Internal carotid artery aneurysm is an uncommon cause of tonsillary asymmetry. Although internal carotid artery aneurysms usually remain asymptomatic, the clinical manifestation requires the tonsillar enlargement. Asymmetry as a sole determining factor for tonsillectomy may lead to unnecessary operations. We report a patient with a giant internal carotid artery aneurysm presenting as tonsillary asymmetry that might be mistaken for a tonsillar neoplasia. When faced with a tonsillar asymmetry, an otolaryngologist must keep aneurysms in mind

Comparison of Cold Technique Tonsillectomy and Thermal Welding Tonsillectomy at Different Age Groups

The aim of this study is to compare objectively advantages and disadvantages of cold technique tonsillectomy and thermal welding tonsillectomy at the same case. A total of 100 patients, 53 patients younger than 12 years of age and 47 patients elder than 12 years of age, were included in this study. Tonsillectomy was performed by using cold technique on the right side of the palatine tonsils and thermal welding on the left side. Right and left sides were compared regarding perioperative bleeding, surgical dissection time, postoperative pain scale at the 1st and 7th day and postoperative bleeding parameters. Perioperative bleeding was found to be higher in cold technique side in patients younger than 12 years of age (p<0.001). Postoperative pain score on the day 1 was significantly higher in cold technique side, whereas it was found to be higher in thermal welding side at postoperative day 7 (p<0.001). Perioperative bleeding was found to be significantly higher in cold technique side (p<0.001) and surgical dissection time of thermal welding was found to be longer (p<0.001) in patients elder than 12 years of age. Postoperative pain score at the day 1 and day 7 was found to be higher in thermal welding side (p<0.001). Postoperative pain score at the day 1 and day 7 were statistically significantly higher in patients elder than 12 years of age. As a result, both techniques have its unique superior aspects and both can be applied as a routine tonsillectomy technique