Tribo-Mechanical Characterization of Carbon Fiber-Reinforced Cyanate Ester Resins Modified With Fillers.

High-performance polymer composites are being increasingly favored for structural applications. For this purpose, efforts are being focused on exploring the potential of high-performance thermoplastics and thermosets. Cyanate ester (CE) resin is a special thermoset that can be used at up to 400 °C without any considerable degradation; however, its tribological properties are not at the adequate level. Hence, it is needed to use this polymer in composite form with the fibrous/particulate reinforcement to impart better tribological properties and mechanical strength via a strong fiber-matrix interface. Carbon fiber/fabrics are at the forefront as reinforcement for specialty polymers. The tribological and tensile properties of cyanate ester (CE) composites-filled graphite, polytetrafluoroethylene (PTFE), and MoS2 micron-sized fillers reinforced with carbon fibers (CF) are investigated experimentally in a block-on-ring setup at 100 N, for 10 h, and with a sliding distance of approximately 10,000 m, against a hardened polished 100Cr6 steel shaft and diamond-like-coated (DLC) 100Cr6 steel shaft. The tribological properties of the composites including the coefficient of friction and specific wear rate are enhanced especially with the incorporation of graphite fillers. The friction coefficient and wear rate of the graphite-based composite was decreased significantly at 5 wt.% of graphite concentration. Further, at the same concentration, the graphite-based composite showed superior tensile properties as compared to the reference system owing to better dispersion and adhesion between the fibers and matrix. Tensile tests are performed to characterize the fiber-matrix interfacial adhesion and other strength properties.

Comparative genomic hybridization-based oncogenetic tree model for genetic classification of breast cancer.

OBJECTIVE: To describe a genetic progression pathway in breast cancer by a maximum likelihood-based tree model representing the dependencies between chromosomal imbalances. STUDY DESIGN: One hundred six cases were studied by comparative genomic hybridization, followed by maximum likelihood estimation of an oncogenetic tree model. RESULTS: The tree model identified 3 clusters with correlated chromosomal imbalances. The first cluster included losses at 4q, 5q, 6q, 9p, 13q and a gain at 17q; the second cluster included gains at 1q, 8q, 16p and 20q; the third cluster included losses at 8p, 11q, 16q and 18q. The imbalances nearest the root of the tree were the loss at 13q (cluster 1), the gain at 1q (cluster 2) and the loss at 18q (cluster 3), reflecting an early change in breast cancer evolution. Cox regression analysis revealed the tumor stage and the grade as relevant for overall survival (p = 0.001) and the tumor stage, the grade and the loss at 16q as relevant for disease-free survival (p = 0.001). CONCLUSION: Methods like oncogenetic tree analysis provide insights into the genetic progression of breast cancer and may extract relevant markers detected by screening methods like comparative genomic hybridization for further studies.

Chromosomal genotype in breast cancer progression: comparison of primary and secondary manifestations.

The purpose of this study was to compare the chromosomal genotype between breast cancers with and without secondary manifestations and between primary tumors and their secondary manifestations. Eighty six breast cancers, twenty lymph node metastases, ten distant metastases and ten local recurrences were analyzed by comparative genomic hybridization. Tumors with local recurrences showed significant more frequent losses at 2q32 than the tumors without recurrences. Lymph node positive cases showed significant more frequent losses at 9p21 than node negative cases. Lymph node metastases exhibited significant more frequent losses at 7q11, 14q24.3-q31 and 17q22-q24 than their primary tumors. In cases with distant metastases, losses at 5q23 were more frequent than in those without, but not reaching the significance level. The distant metastases showed significant more frequent losses at 5p15, 12q24 and 17q22-q24 than the primary tumors. These results reveal strong evidence that the potential for progression is determined in the primary tumor and that different ways of the development of local recurrences, lymph node and distant metastases exist. After confirmation of the results by interphase FISH on tissue micro arrays, the detection of these specific chromosomal imbalances may contribute to a more individual prediction of prognosis in breast cancer.

Diagnostic telepathology: long-term experience of a single institution.

OBJECTIVES: The paper reviews the development of the application of telepathology in a department of surgical pathology between 1991 and 2003. The goal of the efforts during this time was to give up the concept of programming a single application, available only between two fixed workstations with sophisticated devices and special software, and to find the virtual "largest common denominator" for implementing as many different applications as possible with the same basic system. METHODS: A new telepathology system was designed as a client-server system with a relational database at its centre. The clients interact together by transferring the questions (texts and images) to a record (case) in the database on the server and by transferring the answers to the same record on the database. RESULTS: The new "open" telepathology system iPath (http://telepath.patho.unibas.ch) has been very well accepted by many groups around the world. The main application fields are: consultations between pathologists and medical institutions without a pathologist (e.g. for frozen section diagnoses or for surgical diagnoses in hospitals in South Asia or Africa), tumour boards, field studies and distance education (http://teleteach.patho.unibas.ch). CONCLUSIONS: Having observed that with iPath we have succeeded in satisfying all our telepathology needs, we are inclined to put the emphasis on the nature of the tasks being performed, as opposed to the methods or technical means for performing a given task. The three organisation models proposed by Weinstein et al. (2001) can be reduced to only two models: the model of discussion groups and the model of expert groups (virtual institutes).

Metabolic encephalopathies.

Metabolic encephalopathies, usually multifactorial in origin, may be important complications of many diseases of patients treated in a critical care unit. In many cases these complications arise from more than one cause. Neurological signs of metabolic encephalopathies, ancillary tests and differential diagnosis, etiology and pathophysiology are discussed. In this context major single causes for metabolic encephalopathies are referred to. Metabolic encephalopathies as diseases per se (e. g. Wernicke's encephalopathy) and encephalopathies as consequences of deteriorating known diseases (e. g. renal or hepatic diseases) and encephalopathies as complications in patients treated with other diseases in the ICU have to be differentiated. Encephalopathies are known to be the most common complication of a large group of diseases treated in the ICU; on the other hand, manifestation of metabolic encephalopathy can be taken as a warning of deterioration or beginning organ dysfunction. So it would be misleading so far to reduce the clinical concept of metabolic encephalopathies in ICH to septic encephalopathy only.

Decreased plasma and cerebrospinal fluid ascorbate levels in patients with septic encephalopathy.

Septic encephalopathies rapidly affect brain function without the involvement of a specific area causing a broad range of reversible neurologic symptoms. Capillary leakage including dysfunction of the blood-brain barrier has been proposed as a potential pathogenic mechanism in this entity. We tested the hypothesis that oxidative stress measured in plasma and cerebrospinal fluid (CSF) of patients suffering from septic encephalopathy could be linked to the neurologic symptoms of the disease. The neurologic symptoms of eleven patients with septic encephalopathy were described semiquantitatively through a score system. The ascorbate levels were significantly lower in both plasma and CSF from patients with septic encephalopathy than controls, and in CSF but not plasma this decrease correlated with the severity of neurologic symptoms. No significant changes were found for alpha-tocopherol. Our findings suggest that the short-term oxidative stress may be an important factor in the development of septic encephalopathy, possibly through dysregulation of the blood-brain barrier.