A global time-varying sliding-mode control for the tracking problem of uncertain dynamical systems.

In this paper, a global time-varying sliding-mode control scheme with prespecified convergence time is proposed for the tracking problem of a class of uncertain nonlinear systems under parameters uncertainties and external disturbances. Firstly, a novel time-varying sliding manifold with appropriate coefficients is presented. These coefficients are tuned to eliminate the reaching phase and to drive the system states to the equilibrium in a specified time. Hence, the system states are constrained to the sliding surface from the beginning of the motion which enables the global robustness, the reduction of the initial control effort, and the meet of the convergence time requirement. Moreover, in order to address the more practical case that the upper bound of the system uncertainties and disturbances is unavailable, an adaptive time-varying sliding mode control algorithm is derived, by which the tracking error vanish as time tends to infinity. The stability of the system has been proved by the Lyapunov stability theorem, and simulation studies are conducted to show the effectiveness of the suggested control schemes.

Adaptive nonsingular fast terminal sliding-mode control for the tracking problem of uncertain dynamical systems.

In this paper, robust and adaptive nonsingular fast terminal sliding-mode (NFTSM) control schemes for the trajectory tracking problem are proposed with known or unknown upper bound of the system uncertainty and external disturbances. The developed controllers take the advantage of the NFTSM theory to ensure fast convergence rate, singularity avoidance, and robustness against uncertainties and external disturbances. First, a robust NFTSM controller is proposed which guarantees that sliding surface and equilibrium point can be reached in a short finite-time from any initial state. Then, in order to cope with the unknown upper bound of the system uncertainty which may be occurring in practical applications, a new adaptive NFTSM algorithm is developed. One feature of the proposed control law is their adaptation techniques where the prior knowledge of parameters uncertainty and disturbances is not needed. However, the adaptive tuning law can estimate the upper bound of these uncertainties using only position and velocity measurements. Moreover, the proposed controller eliminates the chattering effect without losing the robustness property and the precision. Stability analysis is performed using the Lyapunov stability theory, and simulation studies are conducted to verify the effectiveness of the developed control schemes.

[Cutaneous melanoma: about 200 cases]. / Mélanome cutané: A propos de 200 cas.

AIM: To analyze the clinical and pathological aspects of cutaneous melanoma and to determine the prognostic factors. METHODS: This is a retrospective study about 200 cases of cutaneous melanoma collected in Salah Azaiz Institute over a period of 36 years (1969-2005). RESULTS: The mean age was 55.4 years, with a slight female predominance. The tumour was developed on a pre-existent lesion in 31.5% of cases. The average delay of consultation was 18 months. The mean tumor size was 37 mm (10-180 mm). The ulcero exophytic appearance represented 45% of the cases. The tumor was metastatic in 19.5 % of cases. Hands and feet represented 53% of the tumour localizations. The treatment was curative in 71% of cases and palliative in 13% of cases. The lymph node dissection was performed in 59% of the patients. Histologically, nodular melanoma and Grade V of Clark represented 43.5 and 35% of the cases, respectively. The mean tumoral thickness was 14 mm. Chemotherapy, immunotherapy and radiotherapy were performed in 5.5%, 3.5% and 5.5% of cases respectively. The lymph node recurrences were noted in 43.6% of the patients treated with curative intent. The mean recurrence free survival was 76 months. Tumour size > 2 cm, the localization on the leg, Clark level invasion IV and the involvement of the tumour margin were significant prognostic factors for the recurrence free survival. The prognostic factors for the metastasis free survival were: tumour size, tumour localization, type of resection and finally the lymph node dissection. The 5-year overall survival was 28.5% and was influenced significantly by the tumour size, tumour localization, type of resection, involvement of the tumour margins, Clark grade, tumour thickness and finally the lymph node involvement. CONCLUSION: The dismal prognosis can be improved by early diagnosis and especially the prevention based on the photo protection and surveillance of patients at high risk.

Borderline tumors of the ovary.

BACKGROUND: Borderline tumors of the ovary (BOT) were described for the first time by Taylor in 1929. These lesions have a more favorable outcome than do other ovarian cancers. Their prognosis and treatment are still subject of discussion since they occurred more often in young women where the sparing fertility surgery is always considered primarily. AIM: Evaluate the management of patients with borderline ovarian tumors. METHODS: A retrospective study was conducted in 40 patients with borderline ovarian tumors treated between January 1, 1991 and December 31, 2004. RESULTS: Median follow-up was 43 months, mean age was 44 years. Initial surgery was conservative in 17 patients and radical in 23 cases. Six patients had residual disease. Serous, mucinous and mixte tumors were observed in 18, 21 and 1 cases respectively. Staging was I, II, III in 26, 5, and 9 cases respectively with two pseudomyxomas. Adjuvant Chemotherapy was given in 3 patients. There was a recurrence in 13 patients and seven died. The 5-year overall survival rate was 78 %. Prognostic factors with an impact on survival rate were age, stage of the disease, histological subtype and residual tumor. Factors with a negative impact on recurrence were age, type of surgery and residual disease. With Cox multivariate analysis, residual tumor is an independent factor for overall survival, on the other hand age and type of surgery were significant for recurrence free survival. CONCLUSION: Careful staging followed by complete and radical surgery is mandatory. Unilateral salpingo-oophorectomy with omentectomy and multiple peritoneal biopsies and washing could be indicated in patients with child bearing age. Radical surgery after pregnancy is advised.

Results of second-look laparotomy in advanced ovarian cancer: one single center experience.

Objective. The goal of the study was to analyse the results of 85 cases of second-look laparotomy (SLL) and explore the influence of this procedure on survival. Patients and Methods. We reviewed retrospectively 85 cases of SLL collected and treated in our institute between 1994 and 2003. Results. Complete pathologic response (CPR) was 25.8%, microscopic disease (Rmicro) was 38.8%, and macroscopic disease (Rmacro) was 35.4%. In patients with negative SLL results, disease recurrence was diagnosed in 41%. The 3- and 5-year overall survival rates for the entire population were 91% and 87%, respectively. The 3- and 5-year disease-free survivals were, respectively, 76.3% and 58.5% in negative SLL versus 55.7% and 16% in positive SLL. The difference between the group of patients with complete response (76%) and the patients with residual microscopic disease (72%) was not significant. The tumoral residuum after initial surgery was the only prognostic factor influencing significantly the disease-free survival. On Cox regression model analysis, only initial tumoral residuum (P = 0.04) and tumoral residuum after SLL (P = 0.02) were independent prognostic factors for survival. Conclusions. The most important advantage of SLL is the early detection of recurrence and thus the early administration of consolidation treatment resulting in a better prognosis.

Clinicopathological characteristics of synchronous bilateral breast carcinomas. Report of 30 patients.

AIM: The objective of this study is to determine the clinicopathologic characteristics; incidence and prognosis value of synchronous bilateral breast carcinoma (SBBC). METHODS: This is a retrospective study done in Salah Azaiz Institute of Tunis about 30 patients with synchronous bilateral breast carcinomas diagnosed and treated over a 21-years period going from 1977 to 1997. The definition of synchronous breast lesions is the developpement of the contralateral breast cancer within 6 months. RESULTS: Median age was 49 years. The incidence of SBBC was 0.52%. History family was noted in 3% of our population. Mean tumor size was 40 mm (15-145). Breast conserving therapy was done in 16% of cases (9 patients). Five-year overall survival was 40%. Five year survival rates were 72 and 17% for stage II and III, respectively. Main prognostic factors for survival were lymph node involvement (P=0.004) and disease stage (P=0.02). CONCLUSION: Synchronous bilateral breast carcinoma is a rare entity, with a problem of definition concerning the delay of bilaterlisation. Their prognosis is similar to that of unilateral breast carcinoma patients of equal stage. Hence, breast conserving therapy can be used s fely if indicated.

Breast carcinoma arising within fibroadenomas. Report of four observations.

BACKGROUND: Fibroadenoma is a frequent benign breast tumor affecting young woman. The incidence of a carcinoma within adenofibromas is estimated at 0.1 to 0.3%. AIM: The purpose of this study was to evaluate the outcome of patients with breast carcinoma arising within adenofibroma and to determine the clinical characteristics and the prognosis of this rare entity. OBSERVATIONS: We retrospectively report on four cases of carcinomas arising in mammary fibroadenomas. The mean age was 41 years (26-53). In two cases, fibroadenomas was complex, containing cysts, adenosis and apocrine metaplasia. The adjacent parenchyma contained fibrocystic dystrophy lesions associated in one case to intralobular neoplasia lesions. The treatment consisted of a conservative treatment in two cases and a mastectomy plus axillary node dissection in the two others. Radiotherapy was indicated in all cases and chemotherapy done in three cases. All patients are alive with a mean follow up of 4.25 years (3-7) without any sign of recurrence. CONCLUSION: Every benign mammary nodule must necessarily be verified surgically to avoid misdiagnosing any carcinomatous area because at this stage its prognosis is better.

Recurrent obstructions after resonance stent placement in the treatment of ureteral compression from malignant disease.

BACKGROUND: The Resonance ureteral stent is a newly developed all-metallic double-pigtail ureteral stent allowing a palliative diversion on a patient with malignant ureteral obstruction. AIM: To define selection criteria of good candidates for Resonance stent. CASE: A 62-year-old woman was admitted to the emergency department with complaining of severe right flank pain and anuria. Twelve days earlier, we had placed retrogradely a ureteral metallic Resonance stent (Resonance; Cook Ireland Ltd,Limerick, Ireland) for the treatment of a ureteral compression from pelvic recurrence of an appendical colloid mucosal carcinoma in a solitary functioning right kidney. A percutaneous nephrostomy catheter was placed, and an antegrade nephrostogram demonstrated complete distal ureter obstruction. The patency of the ureteral stent was restored spontaneously and then, nephrostomy catheter was removed. Two weeks later, she presented with obstructed ureteral stent. Percutaneous nephrostomy was performed and Resonance stent was removed definitively. Ureteroscopy with biopsy confirmed the tumour extension into the ureteral lumen. CONCLUSION: The risk of subsequent obstruction after Resonance metallic ureteral stent placement is real. Patients with intra-ureteral tumour extension are presumably not good candidates for Resonance stent management.

Phyllodes tumors of the breast: a case series of 106 patients.

BACKGROUND: Phyllodes tumors (PTs) of the breast are rare, and their prognosis and treatment are still subject of discussion. The purpose of this study is to clarify therapeutic aspects and prognostic factors of this disease. PATIENTS AND METHODS: We retrospectively reviewed the medical records of 106 patients who had histologically confirmed PTs collected over a period of 10 years. RESULTS: The mean age was 39.5 years (14-71 years). The mean tumoral size was 83 mm (15-250). According to criteria of Azzopardi and Salvadori, tumors were classified into 3 groups: benign (62 cases, 58.4%), borderline (16 cases, 15%), and malignant (28 cases, 26.4%). Eighty-two patients (77.4%) were treated conservatively (62 benign, 11 borderline, and 9 malignant) and 24 (22.6%) by radical surgery (5 borderline and 19 malignant). For malignant PTs treated by enucleation or local excision with or without reexcision of the tumor bed, the 5-year overall and disease-free survivals were 28.5% and 15.6% versus 72.7% and 73.6% when the surgery was radical (mastectomy with or without axillary dissection) (P = .12 and P = .0022). For the other histotypes, this difference disappeared. The rate of recurrence was 12.2% (13) after a mean follow-up of 39 months (5 benign, 2 borderline, and 5 malignant). The treatment of recurrences consisted of radical mastectomy (8 cases), simple mastectomy (2 cases), and local excision in 3 cases. Eight patients developed metastases, 2 of whom after recurrences. The 5-year overall and disease-free survivals were 86.54% and 78%, respectively. In univariate analysis, age and recurrences are not of prognostic value for survival, whereas tumor size, histotype, necrosis, cytonuclear atypia, tumor margins, and number of mitosis were significant prognostic factors for survival. In a multivariate study, only cytonuclear atypia remained an independent predictor for survival. CONCLUSION: According to our results, we recommend for malignant PT a simple mastectomy, whereas for borderline and benign PT, treatment is based rather on wide excision passing in healthy tissue.

[Dermatofibrosarcoma protuberans of the breast]. / Dermato fibrosarcome de Darier et Ferrand de siege mammaire.

Dermatofibrosarcoma protuberans is a superficial mesenchymal cutaneous tumor of essentially local malinancy, located more often in the trunk and extremities. This tumor is usually diagnosed after multiple recurrences. We report two cases of rare mammary localisations of dermatofibrosarcoma protuberans in 2 patients aged 39 and 43 years respectively, the two lesions sized 35 x 45 mm were treated by wide excision and reconstruction with a dorsal flap; in the second case.

Prognostic factors and clinicopathologic characteristics of invasive adenocarcinoma of the uterine cervix.

OBJECTIVE: The purpose of this study was to evaluate the outcome of patients with cervical adenocarcinoma and to determine the characteristics and the prognostic factors of this entity. STUDY DESIGN: This retrospective study was done in the Department of Surgical Oncology of the Salah Azaiz Institute of Tunis with 79 cases of invasive adenocarcinoma of the uterine cervix that were collected from 1990 to 1999. Survival was analyzed according to the Kaplan-Meier method. Univariate analysis of prognostic factors was performed with the test of log rank. Cox regression model was used in multivariate analysis of prognostic factors. RESULTS: Mean age was 50 years, and metrorrhagia was mostly revealing in 73% of the cases. Early stages (I, IIa, IIb with 1/3 proximal parametrial invasion) and "pure" type adenocarcinoma were found in 78% and 87% of the cases, respectively. Treatment consisted of a radiosurgical combination in 52 cases; exclusive radiotherapy was practiced with 17 patients. The 5 year-overall and disease-free survival percentages were, respectively, 68% and 72.4%. Poor prognostic factors were age >50 years, tumor size >4 cm, advanced stage, tumor grade, and lymph nodes and lymph-vascular space involvement. With the use of multivariate analysis, only stage and lymph node metastases remained significant prognostic factors. CONCLUSION: This report shows survival and prognostic factors that are similar to those found in previous studies, but unlike the Western countries, our results demonstrate a high rate of early stages and no increase in frequency of cervical adenocarcinoma.