Development of a solar furnace heliostat.

Master of Science in Mechanical Engineering. University of KwaZulu-Natal, Durban 2016.The Solar Energy Research Amplified Flux Facility (SERAFF) is the flagship project of University of KwaZulu-Natal’s Group for Solar Energy Thermodynamics (GSET). SERAFF will assume an on-axis optical configuration, common in solar furnaces around the world, comprising a flat, non-imaging heliostat reflector and a paraboloidal primary concentrator. At design-point conditions, a thermal power output of approximately 5 kW is expected with a peak flux in the region of 3 MW/m2. The facility will provide the University of KwaZulu-Natal with a platform to undertake wide-ranging research in disciplines including concentrating solar power, materials testing and processing, and solar thermochemistry, amongst others. The primary goal of this research was to design and fabricate a flat heliostat which will enable SERAFF to meet the specified thermal requirements. The first phase of this study was to characterise the available solar resource for Durban, South Africa, where SERAFF will be installed. A statistical algorithm was developed that processes historical ground-based solar measurements to generate a continuous function that estimates clear-sky direct normal irradiance (DNI) as a function of solar time and day number over a typical year. The three-dimensional surface that results from this function is termed a temporal DNI topograph (TDT) and can be used to define solar flux input for the modelling of concentrator systems. The heliostat dimensions are dependent on the size of the concentrator aperture it is tasked with illuminating. As such, sizing the concentrator was key. A geometrically based approximation of the maximum theoretical power output of a parabolic primary concentrator was developed. This model was used to calculate the diameter of the parabolic concentrator needed to achieve SERAFF’s specified power output. The model was validated against real solar furnaces around the world and it was found that the model approximated the power output for these solar furnaces within 12% of their published power output values. Following an optical analysis and illumination study, and after taking into consideration the practical and financial constraints placed on the project, it was decided that 3 m x 3 m was the most suitable size for SERAFF’s heliostat. A finite element analysis was used in the design process to assess the survivability (under load from a worst-case wind speed of 100 km/hr) and the rigidity (under load from an operational wind speed of 20 km/hr) for the different heliostat design concepts considered. After analyses of the FEA results it was decided that a classical T-shape design with an aluminium mirror backing frame would be employed. Fabrication of the structural components was undertaken at the department of Mechanical Engineering’s workshop and assembled at a temporary site in close proximity. Consideration was given to the effect the fabrication process would have on the tracking and optical accuracy of the heliostat. The total cost of fabrication was R91,655, exceeding the budget of R85,000 by R6,655. This was due to high import taxes paid on the slewing drive actuator and polished aluminium mirror facets. The actual cost of materials and components was R70,353 excluding the import taxes

A unique case of spontaneous regression of metastatic papillary renal cell carcinoma: a case report

Spontaneous regression of cancer is a rare, but well documented, phenomenon. We present a unique case of an 82 year old Chinese male who experienced spontaneous regression of histologically-verified metastatic type II papillary renal cell carcinoma in the absence of intervening systemic therapy or surgery. This is the first reported case of spontaneous regression of papillary renal cell carcinoma. The mechanism of spontaneous regression remains unknown, and represents a challenge for existing oncology paradigms

Hybrid endoscopic thymectomy : combined transesophageal and transthoracic approach in a survival porcine model with cadaver assessment

BACKGROUND: Video-assisted thoracoscopic surgery thymectomy has been used in the treatment of Myastenia Gravis and thymomas (coexisting or not). In natural orifice transluminal endoscopic surgery, new approaches to the thorax are emerging as alternatives to the classic transthoracic endoscopic surgery. The aim of this study was to assess the feasibility and reliability of hybrid endoscopic thymectomy (HET) using a combined transthoracic and transesophageal approach. METHODS: Twelve consecutive in vivo experiments were undertaken in the porcine model (4 acute and 8 survival). The same procedure was assessed in a human cadaver afterward. For HET, an 11-mm trocar was inserted in the 2nd intercostal space in the left anterior axillary line. A 0° 10-mm thoracoscope with a 5-mm working channel was introduced. Transesophageal access was created through a submucosal tunnel using a flexible gastroscope with a single working channel introduced through the mouth. Using both flexible (gastroscope) and rigid (thoracoscope) instruments, the mediastinum was opened; the thymus was dissected, and the vessels were ligated using electrocautery alone. RESULTS: Submucosal tunnel creation and esophagotomy were performed safely without incidents in all animals. Complete thymectomy was achieved in all experiments. All animals in the survival group lived for 14 days. Thoracoscopic and postmortem examination revealed pleural adhesions on site of the surgical procedure with no signs of infection. Histological analysis of the proximal third of the esophagus revealed complete cicatrization of both mucosal defect and myotomy site. In the human cadaver, we were able to replicate all the procedure even though we were not able to identify the thymus. CONCLUSIONS: Hybrid endoscopic thymectomy is feasible and reliable. HET could be regarded as a possible alternative to classic thoracoscopic approach for patients requiring thymectomy.This project was funded by the FCT Grants project PTDC/SAU-OSM/105578/2008

VATS hand sewn intrathoracic esophagogastric anastomosis

10.21037/jovs.2017.03.26Journal of visualized surgery39

VATS Hand-Sewn Intrathoracic Esophagogastric Anastomosis

<b>Abstract</b><div>Totally endoscopic two-stage esophagectomy for carcinoma of the esophagus is a well-established procedure. There are currently many methods to perform the intrathoracic esophagogastric anastomosis by video-assisted thoracoscopic surgery (VATS). This article describes an entirely hand-sewn VATS intrathoracic esophagogastric anastomosis technique in a 64-year-old woman with a T2N0M0 adenocarcinoma of the lower third of the esophagus.</div><div><br><div><p><b>Preference card</b></p><ol><li>5 mm, 30 degree camera</li><li>5 mm endoscopic needle holder</li><li>4-0 polydiaxone (PDS) sutures</li><li>5 mm endoscopic knot pusher</li></ol><p><b>Tricks and Pitfalls</b></p><ol><li>The first layer of seromuscular-anchoring sutures between the posterior wall of the esophagus and stomach are important for alleviating tension on the anastomosis and for proper alignment of the anastomosis without torsion.</li><li>It is important to perform a circumferential myotomy on the esophagus first and then to cut the mucosal layer long. This ensures the mucosal layer is longer than the muscle layer, prevents retraction of the mucosa into the esophagus, and allows for an accurate mucosal-to-mucosal anastomosis.</li><li>The corner Connell sutures are important in inverting the mucosal layer before the anterior portion of the anastomosis is performed.</li><li>It is mandatory to put port B in the third intercostal space. This gives direct perpendicular access to sewing of both ends. Removing the specimen by enlarging this incision facilitates sewing and tying.</li></ol><div>The full article is avalable at https://www.ctsnet.org/article/vats-hand-sewn-intrathoracic-esophagogastric-anastomosis</div></div></div

Left Video-Assisted Thoracoscopic Enucleation of a Giant Horseshoe Esophageal Leiomyoma

<div>A 27-year-old woman underwent a video-assisted thoracoscopic enucleation of a giant horseshoe esophageal leiomyoma. The patient was asymptomatic and the lesion was discovered incidentally on a routine chest radiograph. Computed tomography (CT) of the thorax showed a 5.5 cm polypoid soft tissue mass in the distal third of the esophagus, causing narrowing and deviation of the lumen anteriorly. Esophagogastroduodenoscopy revealed a large submucosal mass at the distal third of the esophagus. The lesion was imaged as a 45 mm x 25 mm hypoechoic, inhomogeneous mass arising from the muscularis propria on endoscopic ultrasound. Fine needle aspiration (FNA) of the tumor showed a spindle cell tumor consistent with a leiomyoma.</div><div><br></div><div>The patient underwent a VATS excision of the tumor. She was placed in the right lateral decubitus position. The surgeon and camera operator stood in front of the patient for an anterior approach. Three ports were placed in the mid axillary line: a 5 mm camera port in the 6th intercostal space (ICS), a 5 mm working port in the 4th ICS, and a 10 mm working port in the 8th ICS. After lung isolation, the inferior ligament was divided. The mediastinal pleura over the lower third of the esophagus was opened. The lower third of the esophagus, up to the hiatus and EG junction, was completely mobilized due to the circumferential, horseshoe nature of the tumor, which extended to the hiatus. Exposure at the hiatal opening was enhanced with stay sutures. A myotomy over the tumor site was performed until the tumor was seen in the submucosal plane. The tumor was enucleated by sharp and blunt dissection between the muscular and mucosal planes. The tumor was placed in an Endobag and removed by enlarging the 10 mm port. An inadvertent small mucosal tear was made during the enucleation, which was repaired with Prolene 5/0 interrupted sutures. The muscular layer was repaired with interrupted polydiaxone 4/0 sutures.</div><div><br></div><div>An NG tube was placed into the stomach. A chest tube was placed though the lower most 10 mm port, and was removed after 24 hours. The patient was started on nasogastric feeding on the first postoperative day, and was not fed orally for six days. She was discharged home on postoperative day three. A contrast swallow performed on postoperative day six did not demonstrate a leak, with contrast flowing freely into the stomach. Histology of the specimen revealed a 12 cm x 3 cm x 3 cm leiomyoma. The patient remains well at three months’ follow up.</div

Chest wall secondary chondrosarcoma arising from enchondroma in a young Asian female

INTRODUCTION: Enchondromas are benign tumours derived from cartilaginous tissue and they rarely undergo malignant transformation unless they occur in multiple sites such as in the case of Ollier disease. PRESENTATION OF CASE: We report a rare case of a 36-year-old Chinese female, without any past medical history, who had a right chest wall tumour which was initially diagnosed to be benign, for which she was loss to follow up. The mass had been stable in size for the past 7 years until recently, when it gradually grew bigger. computed tomography (CT) scan of the thorax revealed that the mass had invaded the right chest wall suggestive of malignant change. She subsequently underwent an elective open right chest wall resection of the mass and chest wall reconstruction with mesh. A 3 cm by 3 cm tumour arising from the anterior aspect of the 4th rib was found intra-operatively. Post-operative course was uneventful. Histologically, the mass was confirmed to be chrondrosarcoma and resection margins were negative. The patient was discharged on 4th post-operative day and her latest CT thorax during follow up 2 years after operation did not show any tumour recurrence. DISCUSSION: The aim of chest wall reconstruction is to avoid instability and prevent thoracic organs from being exposed if the defect size is ≥10 cm or at least three ribs are resected. Polypropylene mesh may be relatively weak in terms of mechanical support for the chest wall, however, in this case, the defect is not too large and the laterally reflected pectoral muscle can provide enough support together with the mesh. CONCLUSION: Secondary chondrosarcoma in a young Asian female arising from a benign solitary enchondroma in the absence of multiple enchondromatosis, such as Ollier disease or Maffucci syndrome, is extremely rare. Regular follow up including physical assessment and radiological imaging can result in earlier detection of malignant transformation obviating the need for aggressive surgical treatment involving multiple rib resections

Hyperparathyroidism due to eutopic PTH secretion from an ectopic intrathymic parathyroid cyst

10.5761/atcs.cr.10.01634Annals of Thoracic and Cardiovascular Surgery175511 - 51