Crowbar hardware design enhancement for fault ride through capability in doubly fed induction generator-based wind turbines.

A crowbar circuit used in doubly fed induction generator (DFIG)-based wind turbines protects the system during transient stability. However, in a large power system, crowbar protection may be insufficient due to over-voltage and inrush currents occurring during balanced and unbalanced faults. Hence, in this study, a crowbar circuit was enhanced for fault ride through capability against balanced and unbalanced faults in a DFIG. The stator and rotor dynamic modeling used a crowbar hardware circuit design with rotor active impedance. Electromotive force voltages were used for the stator-rotor dynamics in the DFIG. Furthermore, crowbar resistance units were designed to meet the fault ride through DFIG requirement. The DFIG behaviors with and without the crowbar hardware circuit design were compared. The balanced and unbalanced faults were also compared in terms of behavior. Results showed that the circuit design of the crowbar hardware enabled the system to promptly become stable and eliminated the oscillations.

The effect of extracorporeal shock wave lithotripsy on the rat spinal cord.

STUDY DESIGN: Experimental study. OBJECTIVES: To determine the effects of extracorporeal shock wave lithotripsy (ESWL) on the rat spinal cord. METHODS: Animals were randomly divided into three groups. Groups 1 and 2 consisted of five rats each that underwent ESWL (2000 impulses at 15 kV and 2000 impulses at 18 kV, respectively) and group 3 contained five control rats (no shock wave treatment). ESWL-treated and control rats were compared with regard to light and electron microscopic findings of the adjacent spinal cord. RESULTS: Gross neurological outcomes were normal in all groups. Light microscopic examination of group 1 showed extensive extravasation of red blood cells over all the interstitial spaces. Group 2 also had haemorrhagic areas and an irregular organization of axons in the white matter. Transmission electron microscopic examination of group 1 indicated extravasated red blood cells through the endothelium and swollen axoplasm, degenerated mitochondria, destruction of myelin sheaths and a slight increase in the number of lysosomes. Extravasated red blood cells were also seen in group 2. The axoplasmic mitochondria were enlarged, but no sign of mitochondrial degeneration was observed. Lamellar degeneration of myelin sheaths and abundant lysosomes were more predominant in group 2 than in group 1. CONCLUSION: Extracorporeal shock wave lithotripsy caused not only haemorrhage but also damage to neuronal structures except the nucleus. Our findings showed that higher-energy ESWL caused more myelin degeneration in the spinal cord.

Intracranial epidural abscess secondary to isolated sphenoid sinusitis.

Isolated sphenoid sinus infection, although an uncommon entity, can cause severe cranial complications when left untreated. A case of temporal epidural abscess secondary to isolated sphenoid sinusitis in a 13-year-old boy is presented. Early diagnosis and treatment are critical because the disease can progress rapidly.

Antenatal and delivery risk factors and prevalence of cerebral palsy in Duzce (Turkey).

This cross-sectional study aimed at investigating the prevalence and the etiological factors of cerebral palsy (CP) and comparing them with normal population within the rural and urban areas of Duzce province. Of the 102 children with cerebral palsy, 98 were associated with antenatal and delivery risk factors. The mean crude prevalence of cerebral palsy was 1.1 per 1000 live births. The children with CP were compared with 530 control subjects. The mothers of the children with cerebral palsy were significantly younger than the mothers of children in control group, and they had less parity and abortion. Preeclampsia, premature rupture of membranes, home births, prolonged labor, and twin pregnancies were significantly more common in the mothers of children with cerebral palsy, where no significant differences were found between the groups in terms of breech delivery, rate of cesarean births, gestational diabetes, and hemorrhage in late pregnancy. Birth asphyxia, liqueur with meconium stained, prolonged jaundice and neonatal seizure were also significantly more common in the group with cerebral palsy. Of the children with cerebral palsy, 78% were born at term, 20% were born with gestational ages of 32-36 weeks, 2% were born with gestational ages of 30-31 weeks. Nine percent of those children had a birth weight of >or= 3000 g, 12.2% had a birth weight of 2500-2999 g, 33.7% had a birth weight of 1500-2499 g, and 5.1% had a birth weight of

Posterior epidural migration of a lumbar disc fragment causing cauda equina syndrome: case report and review of the relevant literature.

Posterior epidural migration (PEM) of free disc fragments is rare, and reported PEM patients usually presented with radicular signs. An uncommon case involving a patient with cauda equina syndrome due to PEM of a lumbar disc fragment is reported with a review of the literature. The patient described in this report presented with an acute cauda equina syndrome resulting from disc fragment migration at the L3-L4 level that occurred after traction therapy for his lower back pain. The radiological characteristics of the disc fragment were the posterior epidural location and the ring enhancement. A fenestration was performed and histologically confirmed sequestered disc material was removed. An early postoperative examination revealed that motor, sensory, urological, and sexual functions had been recovered. At late follow-up, the patient was doing well after 18 months. Sequestered disc fragments may occasionally migrate to the posterior epidural space of the dural sac. Definite diagnosis of posteriorly located disc fragments is difficult because the radiological images of disc fragments may mimic those of other more common posterior epidural lesions.

Civilian gunshot wounds to the head.

BACKGROUND AND PURPOSE: Civilian Gunshot Wounds (GSWs) to the head are important causes of mortality. The severity of GSWs is related to several factors. Patients with GSWs tend to do very well or very poor depending on these factors. METHODS: We retrospectively reviewed 47 patients with GSWs to the head during the last 5 years. Clinical and radiological findings of cases are described. Statistical analysis was used to find the effects of all independent variables with mortality and the prognostic factors. RESULTS: Glasgow Outcome Scale results showed that 38% of patients died, 13% were moderately disabled and 49% had good recovery at discharge. Patients with respiratory depression, hypovolemia, bilateral pupil dilatation, Glasgow Coma Scale (GCS) scores of 3 to 5, central bihemispheric and transventricular injury experienced 100% mortality. The mortality rate was 58% in patients with intracerebral or subdural hematoma, 78% in multilobar injury, 14% in unilobar injury and 57% in self-inflicted wounds. The postoperative mortality was 27%. CONCLUSION: The manuscript describes the clinical experience of penetrating missile injuries in a Turkish civilian practice. Mortality and/or poor outcome are relatively high in spite of the cases wounded by low-velocity weapons. We should emphasize that following stabilization of vital signs, all patients with GCS scores of 3 to 5 should be evaluated immediately with CT and treated conservatively. If it is appropriate the patients with a GCS score higher than 8 should undergo surgery. Patients with GCS scores of 6 to 8 should be followed closely and treated with surgery when necessary even if they have poor prognosis.

Enterocutaneous fistula: a complication of posterior iliac bone graft harvesting not previously described.

A case of enterocutaneous fistula at the donor site is presented. A patient underwent posterior C5-C6 wire fusion with autologous bone graft taken from the posterior superior iliac crest for degenerative C5-C6 spondylolisthesis. The tip of the osteotome slipped anteriorly during the procurement but neither neurovascular nor peritoneal injury were observed. Spillage of formed faecal material was observed from the donor site on the 12th postoperative day. Fistulogram showed an enterocutaneous fistula to descending colon. The fistula closed spontaneously in a week. Enterocutaneous fistula after bone harvesting has never been reported in the literature as far as we know. Congenital malformations and acquired causes may create a vulnerable peritoneal area. Small bowel or descending colon may show a close relationship or even an adhesion to peritoneum in the presence of local peritonitis. A small lesion in this area may play a role in the occurrence of a fistula, and a low flow pseudofistulous tract may appear. The thermal injury and possible ischaemic necrosis due to cauterisation may be predisposing factors in the aetiology of this kind of fistula. The lack of foreign material and spontaneous closure were against an infectious origin. The aims of this report are to present and analyse the reasons of this complication, not previously described.

The functional independence measure in spinal cord injured patients: comparison of questioning with observational rating.

Functional independence measure (FIM) is becoming widely used for all aspects of disabling diseases including spinal cord injury (SCI). It is recommended that it is rated by trained clinicians familiar with the patients. We aimed to compare the ratings of those patients who were questioned with those who were observed in a simulated environment. Fifty patients with SCI were included in the study. They were all FIM rated by the same clinician, first by questioning and then by observation. Although observational rating took much more time than questioning there was a very strong correlation between these two different rating methods. We can conclude that questioning SCI patients could be used as a valuable and quick way to assess the functional level of such patients. Although this does not exclude observational scoring that was generally higher and more motivational for the patient.

Traumatic spinal cord injuries in Istanbul, Turkey. An epidemiological study.

This is a retrospective study conducted in all of the hospitals of Istanbul to survey new patients with a traumatic spinal cord injury (SCI) in 1992. In that year 152 new traumatic SCI were identified. The estimated annual incidence was 21 per million population. The male/female ratio was 3/1. The mean age was 33, being 34 for male patients and 31 for female patients. 72% of all patients were under the age of forty. The major causes of SCI were falls (43%) and car accidents (41%), followed by being struck by an object (7%), gunshot injury (5%), stab injury (2%). Fifty patients (33%) were tetraplegic and 102 (67%) paraplegic. Regarding the tetraplegic patients the commonest level was C5, in those who were paraplegic L1. There were no cases at levels C1, T1 or T2. The commonest associated injury was head trauma, followed by fractures of an extremity (or extremities). Severe head trauma, as a major cause of death, may obscure the actual incidence of SCI in this study. Accidental falls (exceeding road accidents) were mostly due to falls from buildings and accidents on work premises.