Risk factors for graft failure after penetrating keratoplasty

The objective of our study was to define principal risk factors for graft failure in patients who underwent penetrating keratoplasty (PK).Retrospective data obtained from a cohort of 895 penetrating keratoplasties performed between 2001 and 2006 were analysed. Recipient related factors, graft characteristics, and surgical technique were assessed in a univariate analysis and with a multivariate proportional hazard model to detect principal risk factors for definitive graft failure.Multivariate analysis showed clear significance for diagnosis and number of previous grafts and border line significance for the oldest donor age group. Patients with keratoconus had the best 10-year survival estimate (95%), followed by endothelial and stromal dystrophies (both 55%), infectious leukomas (49%), trauma (33%) and chemical burns (14%). Primary PK grafts had a survival rate of 81%, second grafts of 33% and third or more grafts of 16%. Overall 10-year survival estimate based on univariate analysis was found to be 65%.In conclusion, we found that primary diagnosis and previous graft failures in the recipient are the most important risk factors of graft failure after a PK

Acute leukemia in association with Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) and malignancy occurring in the same individual is unusual and has generally been the subject of isolated case reports. To better define the occurrence of these events a registry of cases with synchronous or asynchronous LCH and malignancy was developed with the cooperation of the Histiocyte Society. In 1991 the Histiocyte Society surveyed its members requesting information on cases in which LCH was associated with malignancy. The questionnaire was mailed to all members of the society and specifically requested information on the clinical and laboratory features of the cases, disease evolution, and response to therapy. Retrospective reporting was allowed. With this initial data, an ongoing registry of LCH patients with associated malignancy was begun of such cases, including evolution and response to therapy. Twenty-seven patients were enrolled during the first year of the registry, of whom 4 patients had the association of LCH with a malignant lymphoma and 10 cases had an association of LCH with other types of solid tumor. The remaining 13 patients had the association of LCH with acute leukemia. In five cases, LCH was associated with acute lymphoblastic leukemia FAB L1 (ALL). In four cases the ALL preceded the LCH by 6 months to 1 year. In four of five patients the LCH was localized; in two instances the LCH was treated with chemotherapy. In all cases the leukemia was treated according to local standard ALL protocols and in one case autologous bone marrow transplantation (ABMT) was performed at relapse. Three patients are free of leukemia, one of whom has persistent localized LCH of the skin. Two patients died of the ALL, one of whom was free of the LCH at the time of death. In eight instances LCH was reported in association with acute myeloid leukemia (AML). Six of these patients had a generalized form of LCH. In seven the diagnosis of LCH preceded the diagnosis of leukemia by more than 2 years (median 4 years). In the remaining patient both diagnoses were made concurrently. In all seven cases in whom LCH was the initial diagnosis the treatment consisted of chemotherapy and/or radiotherapy. Seven patients died from the AML, five without evidence of LCH. The temporal patterns of the LCH-ALL and LCH-AML associations are distinct with ALL usually preceding the diagnosis of LCH and AML succeeding it. Such a pattern is suggestive that in cases of ALL the LCH may be a reactive process while in cases of AML occurring after LCH the primary LCH therapy may play an inductive role in the leukemia. © 1994 Wiley-Liss, Inc

Recognition of Intentional Violations of Active Constraints in Cooperative Manipulation Tasks

Active Constraints (ACs) are high-level control algorithms deployed to assist a human operator in man-machine cooperative tasks [1], and define regions within which it is safe for the robot to move and cut [2]. To enhance the performance in cooperative surgical tasks, adaptive constraints have been exploited to optimally adjust the provided level of assistance according to some knowledge of the task, hardware or user. In [3] Hidden Markov Models were used for the run-time detection of the user intention to leave a guidance constraint to circumvent an obstacle. In this work, we present a novel, Neural Network (NN)-based method for the runtime classification of intentional and unintentional violations of ACs, that is trained on either statistical or frequency features from the enforced constraint forces. We investigate which set of parameters yield faster and more reliable classification results, both for guidance and regional constraints

Influence of TiO2 nanometric filler on the behaviour of a composite membrane for applications in direct methanol fuel cells

Composite Nafion membranes containing various amounts of TiO2 (3 wt%, 5 wt% and 10 wt%) were investigated for operation in high temperature Direct Methanol Fuel Cells (DMFCs). Maximum power density of 350 mW cm -2 was achieved in the presence of oxygen feed at 145°C for the composite membranes containing 3-5 wt% TiO2; whereas, the maximum power density with air feed was about 210 mW cm-2. Moreover, an investigation of the influence of titanium oxide particle size on the electrochemical behaviour of the composite membranes for high temperature operation has been carried out. The DMFC performance increases as the mean particle size of the TiO2 filler decreases. This indicates an influence of the filler morphology on the electrochemical properties of the composite membranes. © J. New. Mat. Electrochem. Systems

Synthesis, Characterization and Electrocatalytic Activity of Bi- and Tri-metallic Pt-Based Anode Catalysts for Direct Ethanol Fuel Cells

Three Pt-based anode catalysts supported on Vulcan XC-72R (VC) were prepared by using a modified polyol process. These materials were characterized and tested by X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) and Transmission Electron Microscopy (TEM). XRD and TEM analysis indicated that especially the ternary anode catalysts consisted of uniform nanosized particles with sharp distribution. The Pt lattice parameter was smaller, in the ternary PtSnIr catalyst whereas it increased with the addition of Sn and Rh, in the corresponding binary and ternary catalysts. Cyclic voltammetry (CV) measurements showed that Sn, Ir and Rh may act as promoter of Pt enhancing ethanol electro-oxidation activity. It was found that the direct ethanol fuel cell (DEFC) performances were significantly improved with these modified anode catalysts. This effect on the DEFC performance is attributed to the so-called bi-tri-functional mechanism and to the electronic interaction between Pt and additives. The performance increased significantly with the temperature. However, it was also possible to observe some decay with time for all catalysts due to the formation of surface poisons, probably consisting in CO-like species. At 60 °C, the PtSnIr catalyst showed the best performance, as a result of a proper morphology and promoting effectFil: D'Urso, C.. Centro Nazionale della Ricerca. ITAE; ItaliaFil: Bonesi, Alejandro Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Triaca, Walter Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Castro Luna Berenguer, Ana Maria del Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Baglio, V.. Centro Nazionale della Ricerca. ITAE; Italia; ItaliaFil: Aricò, A. S.. Centro Nazionale della Ricerca. ITAE; Italia; Itali

Synthesis, Characterization and Electrocatalytic Activity of Bi- and Tri-metallic Pt-Based Anode Catalysts for Direct Ethanol Fuel Cells

Three Pt-based anode catalysts supported on Vulcan XC-72R (VC) were prepared by using a modified polyol process. These materials were characterized and tested by X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) and Transmission Electron Microscopy (TEM). XRD and TEM analysis indicated that especially the ternary anode catalysts consisted of uniform nanosized particles with sharp distribution. The Pt lattice parameter was smaller, in the ternary PtSnIr catalyst whereas it increased with the addition of Sn and Rh, in the corresponding binary and ternary catalysts. Cyclic voltammetry (CV) measurements showed that Sn, Ir and Rh may act as promoter of Pt enhancing ethanol electro-oxidation activity. It was found that the direct ethanol fuel cell (DEFC) performances were significantly improved with these modified anode catalysts. This effect on the DEFC performance is attributed to the so-called bi-tri-functional mechanism and to the electronic interaction between Pt and additives. The performance increased significantly with the temperature. However, it was also possible to observe some decay with time for all catalysts due to the formation of surface poisons, probably consisting in CO-like species. At 60 °C, the PtSnIr catalyst showed the best performance, as a result of a proper morphology and promoting effectFacultad de Ciencias ExactasInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada