Fragmentation processes in two-phase materials.

We investigate the fragmentation process of solid materials with crystalline and amorphous phases using the the discrete element method. Damage initiates inside spherical samples above the contact zone in a region where the circumferential stress field is tensile. Cracks initiated in this region grow to form meridional planes. If the collision energy exceeds a critical value which depends on the material's internal structure, cracks reach the sample surface resulting in fragmentation. We show that this primary fragmentation mechanism is very robust with respect to the internal structure of the material. For all configurations, a sharp transition from the damage to the fragmentation regime is observed, with smaller critical collision energies for crystalline samples. The mass distribution of the fragments follows a power law for small fragments with an exponent that is characteristic for the branching merging process of unstable cracks. Moreover this exponent depends only on the dimensionally of the system and not on the microstructure.

The surgical management of parotid gland tumours.

BACKGROUND: The parotid tissue can give rise to a large variety of benign and malignant neoplasms. The objective of this study was to describe the management and outcome of parotid gland tumours over a 15-year period. METHOD: The records of consecutive patients treated by parotid gland excision from January 1995 to December 2008 were reviewed retrospectively. Data recorded were age, gender, history, physical findings, surgical procedure, fine-needle aspiration biopsy (FNAB), final pathological diagnosis and complications. RESULTS: The vast majority of patients (306) had benign neoplasms, and 14 patients had malignant neoplasms. Overall, pleomorphic adenoma contributed to 76% of the lesions, and Warthin's tumour to 17%. The sensitivity and specificity of FNAB was 79% and 100%, respectively. There were 15 cases of marginal mandibular transitory paresis and 12 cases of seroma. Marginal mandibular definitive paralysis was observed in three cases with malignant tumour. CONCLUSION: Standardised parotidectomy is a safe operation, with a low complication rate.

Stapler suture of the pharynx after total laryngectomy.

The use of a stapler for pharyngeal closure during total laryngectomy was first described in 1971. It provides rapid watertight closure without surgical field contamination. The objective of our study was to compare the incidence of pharyngocutaneous fistula after total laryngectomy with manual and mechanical closures of the pharynx. This was a non-randomised, prospective clinical study conducted at two tertiary medical centres from 1996 to 2011 including consecutive patients with laryngeal tumours who underwent total laryngectomy. We compared the incidence of pharyngocutaneous fistula between two groups of patients: in 20 patients, 75 mm linear stapler closure was applied, whereas in 67 patients a manual suture was used. Clinical data were compared between groups. The groups were statistically similar in terms of gender, age, diabetes mellitus, smoking and alcohol consumption and tumour site. The group of patients who underwent stapler-assisted pharyngeal closure had a higher number of patients with previous tracheotomy (p < 0.001) and previous chemoradiation (p < 0.001). The incidence of pharyngocutaneous fistula was 30% in the mechanical closure group and 20.9% in the manual suture group (p = 0.42). In conclusion the use of the stapler does not increase the rate of fistulae.

Contact endoscopy for identifying the parathyroid glands during thyroidectomy.

Aim of this study was to analyse contact endoscopy as an auxiliary method for identifying parathyroid glands during thyroid surgery and to identify other variables that may interfere with this correlation. Overall, 125 patients underwent thyroid surgery between January 2004 and February 2006. The variables analysed were: the total duration of surgery; time taken to locate and identify parathyroid glands; improvement in identifying these; numbers of parathyroid glands located by the surgeon and confirmed by contact endoscopy; histopathological diagnosis; presence of thyroiditis; thyroid weight; number of parathyroid glands left in thyroid specimens; and number of parathyroid gland autotransplantations. A total of 331 parathyroid glands were observed by the surgeon. However, 282 glands were identified by contact endoscopy. Nine parathyroid glands (7.2%) were observed together with thyroid specimens (Kappa = 0.534). The longer the total duration of surgery (p = 0.03) and time taken to locate and identify (p = 0.00) the parathyroid glands by contact endoscopy, the lower the observed agreement. The second year of performing contact endoscopy led to better agreement between the results (p = 0.02). In conclusion, contact endoscopy is an efficient auxiliary method for identifying parathyroid glands during thyroid surgery. During the period studied, association between total duration of surgery and time taken to locate and identify parathyroid glands was statistically significant.

Contact endoscopy of the larynx as an auxiliary method to the surgical margins in frontolateral laryngectomy.

Contact laryngomicroscopy is in vivo laryngeal mucosa microscopic examination and rigid telescopy is a non-invasive technique that enables the systematic observation of many details in the large area of vocal fold mucosa. These are performed during laryngomicroscopy. This study was performed in order to evaluate the use of rigid and contact endoscopy effectiveness in establishing the margins in patients undergoing frontolateral laryngectomy. Ten patients with glottic squamous cell carcinoma underwent frontolateral laryngectomy from 2000 to 2003. Eight were staged as T1bN0M0, whereas two were staged as T2N0M0. During the frontolateral approach, the lesion and its limits were carefully defined, the surgical margins were established under the rigid telescope and the patients' margins were studied under contact endoscopy after methylene blue staining. Frozen section examination of the margins was performed and the histopathological analysis was compared to the surgical and endocopic findings. The infraglottic region and the surgical margins were free of disease in all cases and there was a 100% correlation with the histopathological examination. All patients are alive with no evidence of disease after a minimum of 5 years' follow-up. In conclusion, rigid and contact laryngoscopy is effective in establishing the disease-free surgical margins in patients submitted to frontolateral laryngectomy.

Performance of constructed wetland systems treating anerobic effluents.

The purpose of this present paper is to verify the performance of three wetland systems operated with effluents from a UASB reactor, with respect nutrient removal (nitrogen and phosphorus), pathogenic organisms and remaining carbonaceous material, monitored over a three-year period. The experiment was carried out and monitored at PROSAB (Programa de Saneamento Básico) in Campina Grande, Paraíba. The removal efficiency of the carbonaceous material expressed in DQO ranged from 70 to 86%, but concerning the total suspended solids, the efficiency ranged from 50 to 71%. The removal efficiency in terms of nitrogen and phosphorus of both vegetated systems was about 65.5 to 86%, respectively, during the first year of operation. Under the operational conditions of the experiment, the removal of phosphorus in a wetland system containing washed sand as the substratum decreased, as its operation period increased. The vegetated wetland has been the most efficient in removing faecal coliforms (roughly 4 log units) as compared to the non-vegetated one (about 3 log units), when both were operated with the same hydraulic load (2.3 cm. per day). Thus, the effluent produced over the three-year period ranged from 800 to 1,800 UFC/100 mL in the analyzed samples.

Papillary thyroid carcinoma in thyroglossal duct cyst.

Thyroglossal duct remnants are the most common midline neck swellings, but carcinoma is found in approximately 1% of these lesions. The cysts are usually asymptomatic and the presentation of the patient with carcinoma is indistinguishable from the common cyst. Papillary adenocarcinoma comprises 75-85% of the tumors reported. A 36-year-old woman underwent Sistrunk procedure for excision of a thyroglossal cyst. No thyroid abnormality was noted pre-operatively nor during the surgical examination. The histopathological examination revealed papillary carcinoma. She has been maintained on thyroxine suppression and was doing well at 14 months' follow-up. Carcinoma of the thyroglossal duct cyst is rare. The ultrasonographic examination should be performed pre-operatively for thyroid gland study. The main question is what to do with the thyroid gland. There still is controversy about thyroid removal for a papillary carcinoma, but all the patients should receive suppressive doses of thyroid hormone. As the cure rate is 95% for the patients whose thyroid is preserved and further postoperative complications are avoided, we can consider that the optimal surgical procedure for thyroglossal duct carcinoma is the same as that for the benign cyst.

Surgical treatment of the substernal goitre.

This report describes the surgical experience gained from 32 patients with substernal goitre, operated on during January 1995 to December 1997. The material corresponds to 15.7% of the total thyroidectomies performed. The diagnosis was clinical. In spite of 65.6% of the patients being asymptomatic, breathing problems, dysphagia and hyperthyroidism were observed. The patients underwent tests of thyroid function, simple chest radiograph and computerized tomography of mediastinum. All patients underwent surgical treatment through a transverse cervical incision. Two patients (6.25%) needed median sternotomy. Vocal cord palsy (3.12%), transient hypocalcemia (6.25%) and one death due to cardiac causes (3.12%) were the complications that occurred.

In situ saphenous vein arterial bypass for infrainguinal revascularization: initial experience using an open technique.

The authors describe their initial experience with the use of the in situ saphenous vein arterial by-pass technique for infrainguinal revascularization. From December 1986 to August 1989, we performed 101 in situ saphenous vein arterial by-passes. From these 101 by-pass, 18 composite or partial in situ vein by-passes (in situ + reversed vein) and 2 extra-anatomical sequencial by-passes (one axillofemoral and one cross-over femorofemoral proximal by-passes extended by in situ saphenous vein femoropopliteal arterial by-passes) were withdrawn from the statistics, with the purpose of analysing the natural evolution of the in situ vein arterial by-pass without the insertion of reversed vein segments and/or the influence of artificial grafts to improve arterial inflow. Therefore only 81 in situ by-pass cases will be analysed in the present paper. From these 81 cases, 44 (54.3%) were performed in diabetic patients and limb salvage was the indication for by-pass in 63 (81%). The saphenous vein valves were rendered incompetent utilising the retrograde Mills-Leather valvulotome and exposing the greater saphenous vein with a continuous incision. In the 81 cases, wound complications occurred in 18 limbs (22%) and operative mortality (30 days) was 6.1%. Primary cumulative patency rate of the 81 cases was 77% and secondary cumulative patency rate was 80%, at the end of the analysed period. The open technique, using a retrograde valvulotome and exposing the entire conduit of the greater saphenous vein, became our preferred technique for infrainguinal revascularization.