No description available.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 74-75). Also available via the Internet.

Thèse--Liège. / Photocopy of typescript. Includes bibliographical references. Also issued in print.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 267-273). Also available via the Internet.

Thèse--Liège. / Photocopy of typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Universiẗat, Diss., 2001--Tübingen.

Sphenoid wing meningiomas are benign tumors that result in proptosis, visual impairment and pain. Traditional open surgical approaches are associated with significant morbidity. Transorbital endoscopic surgery has been developed as a minimally invasive approach to gain access to these tumors and address the main presenting symptoms. The aim of the study was to assess long term vision and proptosis outcomes in patients undergoing a transorbital endoscopic resection of sphenoid wing meningioma using a combined endonasal, precaruncular and extended superior eyelid approach and to describe the surgical approach. Materials &amp; Methods A retrospective chart review was conducted in 21 patients with lateral sphenoid wing meningioma at Groote Schuur Hospital &amp; Cape Town Mediclinic from 2015–2019. All patients had undergone a transorbital endoscopic subtotal resection (Simpson grade II – IV) by the same surgical team. Vision was assessed using a Snellen chart and proptosis measured in mm using a Hertel exophthalmometer by an ophthalmologist. Measurements were taken at 6 weeks, 6 months and at 1 year postoperatively and compared to pre-operative values. Patients were categorized according to the WHO classification of vision into group A (blind), group B (low vision) &amp; group C (normal vision) according to their pre-operative visual acuity. Nonparametric statistical tests employing the Wilcoxon Signed-Ranks Test were used for analysis. Statistical significance was determined by a confidence interval of 0.95, p = < 0.05 for both visual acuity (converted to LogMar) and proptosis in mm. Results A total of 21 patient charts were reviewed. The mean age of presentation was 48.8 years (range 34-79 years), and the majority of patients were female (20/21 = 95%). The most common presenting complaints were loss of vision (100%), proptosis (95%) and headache (76%). Preoperative visual results were as follows: 10 (48%) in group A (blind), 4 (19%) in group B (low vision) and 7 (33%) in group C (normal vision). In group A, 6 (60%) remained unchanged, 2 (20%) deteriorated &amp; 1 (10%) improved. In group B, 3 (75%) improved, and 1 (25%) remained stable. In group C, 5 (71%) improved and 2 (29%) remained stable. Vision in groups B &amp; C showed no deterioration. Patients in group A showed no benefit from optic nerve decompression. Vision in groups B &amp; C showed a statistically significant improvement at 6 weeks [95% CI] (p = 0.021). This trend extended to long term follow up at 6 months [95% CI] (p= 0.021) and 1 year [95% CI] (p = 0.0054) postoperatively. Proptosis initially decreased, proving statistical significance at 6 weeks [95% CI] (p = 0.0054) postoperatively. The decrease at 6 months (p = 0.08) was not statistically significant and trended towards an increase in proptosis by 1 year (p = 0.78) postoperatively. The mean hospital stay was 2.7 days (range 2 – 4 days). The majority of tumors were histologically classified as WHO grade I. Conclusion Endoscopic medial optic canal decompression prior to transorbital multiportal surgery for sphenoid wing meningioma stabilizes or improves visual acuity for at least 1 year. Lateral orbitotomy via a superior eyelid approach and subtotal tumor resection initially decreases proptosis, but in the long term, returns to its preoperative state by 1 year if the main tumor component is not addressed. The earlier that medial optic nerve decompression is performed and the better the preoperative visual acuity, the greater the likelihood of favorable long-term visual outcomes.

No description available.

This thesis presents an approximate solution of second order relative motion equations. The equations of motion for a Keplerian orbit in spherical coordinates are expanded in Taylor series form using reference conditions consistent with that of a circular orbit. Only terms that are linear or quadratic in state variables are kept in the expansion. A perturbation method is employed to obtain an approximate solution of the resulting nonlinear differential equations. This new solution is compared with the previously known solution of the linear case to show improvement, and with numerical integration of the quadratic differential equation to understand the error incurred by the approximation. In all cases, the comparison is made by computing the difference of the approximate state (analytical or numerical) from numerical integration of the full nonlinear Keplerian equations of motion. / Master of Science

Orientador: Rodolpho Vilhena de Moraes / Banca: Othon Cabo Winter / Banca: Claudia Celeste Celestino / Resumo: No presente trabalho é abordada a manobra orbital Terra-Lua - Terra com o objetivo de um menor consumo de combustível. Inicialmente o satélite executa uma órbita em torno da Terra. Em um certo instante um impulso é efetuado para efetuar uma manobra não con-focal em que o satélite é transferido para uma órbita de transferência geocêntrica até um ponto da esfera de influência da Lua. A partir deste ponto o satélite é transferido para uma órbita hiperbólica em torno da Lua, e, no perilúnio desta órbita um novo impulso é dado transferindo o satélite para uma órbita lunar. A seguir é efetuada a manobra de volta em que o satélite é transferido para a órbitra geocêntrica de transferência, e no pericentro desta o satélite é transferido para a sua órbita inicial em torno da Terra. O caso não coplanar e a influência das perturbações devidas ao achatamento da Terra e a atração gravitacional da Lua também são analisados. / Abstract: In the present work an Earth-Moon-Earth orbital maneuver is studied with the purpose of minimum fuel consumption. Initially it is considered an artificial satellite orbiting around the Earth. In a certain instant an impulse is effected to effect a not cofocal maneuver where the satellite is transferred to an orbit of geocentric transference until a point of the sphere of influence of the Moon. From this point the satellite is transferred to a hyperbolic orbit around the Moon, and, in the perilúnio of this orbit a new impulse is given transferring the satellite to a lunar orbit. To follow the maneuver is effected in return where the satellite is transferred to geocentric orbit of transference, and in pericentro of this the satellite is transferred to its initial orbit around the Earth. The non-coplanar case and the influence of the disturbances due to the flattening of the Earth and the gravitational attraction of the Moon also are analyzed. / Mestre