220 research outputs found

    Mechano-energetics of the asynchronous and resynchronized heart

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    Abnormal electrical activation of the ventricles creates major abnormalities in cardiac mechanics. Local contraction patterns, as reflected by measurements of local strain, are not only out of phase, but often also show opposing length changes in early and late activated regions. As a consequence, the efficiency of cardiac pump function (the amount of stroke work generated by a unit of oxygen consumed) is approximately 30% lower in asynchronous than in synchronous hearts. Moreover, the amount of work performed in myocardial segments becomes considerably larger in late than in early activated regions. Cardiac Resynchronization Therapy (CRT) improves mechano-energetics of the previously asynchronous heart in various ways: it alleviates impediment of the abnormal contraction on blood flow, it increases myocardial efficiency, it recruits contraction in the previously early activated septum and it creates a more uniform distribution of myocardial blood flow. These factors act together to increase the range of cardiac work that can be delivered by the patients’ heart, an effect that can explain the increased exercise tolerance and quality of life reported in several CRT trials

    Applications of Genetic Programming to Finance and Economics: Past, Present, Future

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    While the origins of Genetic Programming (GP) stretch back over fifty years, the field of GP was invigorated by John Koza’s popularisation of the methodology in the 1990s. A particular feature of the GP literature since then has been a strong interest in the application of GP to real-world problem domains. One application domain which has attracted significant attention is that of finance and economics, with several hundred papers from this subfield being listed in the Genetic Programming Bibliography. In this article we outline why finance and economics has been a popular application area for GP and briefly indicate the wide span of this work. However, despite this research effort there is relatively scant evidence of the usage of GP by the mainstream finance community in academia or industry. We speculate why this may be the case, describe what is needed to make this research more relevant from a finance perspective, and suggest some future directions for the application of GP in finance and economics

    Identity Disturbances and Self-other Differentiation in Schizophrenics, Borderlines, and Normal Controls

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    The present study investigates identity disorders in schizophrenics and borderlines. Nineteen schizophrenics and 17 borderlines were compared with 18 normal controls. The technique used was an adapted version of the repertory grid test to describe the self and nine significant others (i.e., family members). Three indices were derived from the 10 person x 20 self-generated-attribute matrix to measure the extent to which self was differentiated from others: (1) overlap of salient attributes, (2) overlap of opposite attributes, and (3) degree of differentiation among others. Results showed that both schizophrenics and borderlines describe themselves more in terms of opposites than in terms of salient attributes. Differentiation among significant others was severely impaired in schizophrenics and preserved in borderlines. These findings were interpreted as a failure of the individuation process in schizophrenics and as an incomplete construal of self-identity in borderlines. (C) 1995 by W.B. Saunders Compan

    Small intestinal brush border enzymes in cystic fibrosis

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    The study concerns the maltase, saccharase, lactase and alkaline phosphatase activity in small intestinal biopsy specimens from 61 consecutively admitted, untreated, Caucasian cystic fibrosis patients. A group of 319 age matched controls admitted during the same time period for undefined gastrointestinal or nutritional disorders acted as the controls. In order to eliminate morphological damage as a confounding factor, the enzyme activities were studied in small intestinal biopsy specimens having both normal stereomicroscopic and histological features. It was shown that neither maltase nor saccharase activity was different in the two groups, in contrast to lactase and alkaline phophatase activity, that was significantly lower in cystic fibrosis patients. The differences could not be explained by the nutritional status as judged by the body mass index. Lactase activity is known to be easily affected by numerous enteropathies. As the information on alkaline phosphatase activity is limited, the low activity is discussed in more detail. Taking into account the literature data, the low alkaline phophatase activity is tentatively attributed either to enhanced release from the brush border or to the faulty handling of alkaline phophatase protein in the post-golgi compartments secondary to the accumulation of incorrectly glycosylated CFTR in the same cell structures
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