Classification by clustering decision tree-like classifier based on adjusted clusters

Currently cluster analysis techniques are used mainly to aggregate objects into groups according to similarity measures. Whether the number of groups is pre-defined (supervised clustering) or not (unsupervised clustering), clustering techniques do not provide decision rules or a decision tree for the associations that are implemented. The current study proposes and evaluates a new technique to define decision tree based on cluster analysis. The proposed model was applied and tested on two large datasets of real life HR classification problems. The results of the model were compared to results obtained by conventional decision trees. It was found that the decision rules obtained by the model are at least as good as those obtained by conventional decision trees. In some cases the model yields better results than decision trees. In addition, a new measure is developed to help fine-tune the clustering model to achieve better and more accurate results.     

Prospective motion correction of X-ray images for coronary interventions

A method for prospective motion correction of X-ray imaging of the heart is presented. A 3D + t coronary model is reconstructed from a biplane coronary angiogram obtained during free breathing. The deformation field is parameterized by cardiac and respiratory phase, which enables the estimation of the state of the arteries at any phase of the cardiac-respiratory cycle. The motion of the three-dimensional (3-D) coronary model is projected onto the image planes and used to compute a dewarping function for motion correcting the images. The use of a 3-D coronary model facilitates motion correction of images acquired with the X-ray system at arbitrary orientations. The performance of the algorithm was measured by tracking the motion of selected left coronary landmarks using a template matching cross-correlation. In three patients, we motion corrected the same images used to construct their 3D + t coronary model. In this best case scenario, the algorithm reduced the motion of the landmarks by 84%-85%, from mean RMS displacements of 12.8-14.6 pixels to 2.1-2.2 pixels. Prospective motion correction was tested in five patients by building the coronary model from one dataset, and correcting a second dataset. The patient's cardiac and respiratory phase are monitored and used to calculate the appropriate correction parameters. The results showed a 48%-63% reduction in the motion of the landmarks, from a mean RMS displacement of 11.5-13.6 pixels to 4.4-7.1 pixels.     

Determination of free choline and phosphorylcholine in rat liver

A simple procedure for the determination of levels of free choline and phosphorylcholine in hepatic tissue is outlined. The method makes use of the enzyme acid phosphatase to liberate choline from phosphorylcholine and incorporates the ability of choline to react with potassium triiodide to yield choline periodide for the measurement of choline and phosphorylcholine in liver. The method is accurate for both entities (recovery of 97–100% for choline and 92–98% for phosphorylcholine). For phosphorylcholine, the method is markedly simpler than other methods previously described and the results for normally fed rats are of the same order of magnitude. The applicability of the method was shown when it was demonstrated that diets containing different amounts of choline influenced the level of choline and phosphorylcholine in liver.     

Effect of serum lipoproteins of bile obstructed rats on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in perfused rat liver

Total lipoproteins as well as fractionated VLDL+LDL and HDL from fasted control rats and bileligated rats were tested in liver perfusion for their effect on 3-hydroxy-3-methylglutaryl CoA reductase to increase 3-hydroxy-3-methylglutaryl CoA reductase activity than that of the control total lipoproteins. When the fractionated lipoproteins were tested from fasted control rats, it was found that the major stimulating activity was in the HDL fraction with minor activity in the VLDL+LDL fraction. When these plasma components isolated from fasted bile-ligated rats were tested, it was found that the major activity had shifted to the VLDL+LDL fraction with the HDL having only a minor stimulatory role. The possible mechanism of action of the abnormal lipoproteins associated with bile obstruction in regulating 3-hydroxy-3-methylglutaryl CoA reductase activity is discussed.     

Classification by clustering using an extended saliency measure

In many data mining tasks, the goal is to classify entities into a set of pre‐defined groups (classes). A second and equally important goal is the interpretation, i.e. understanding the nature of the population aggregated in each class. These tasks are rendered even more complex when there is no a‐priori information regarding the right classification. The current paper is based on two concepts: (1) Bounded‐Rationality theory which implements an S‐shaped function that represents human logic as a saliency measure to determine the substantial features that characterize each potential group and (2) Classification by clustering (CBC) that applies Decision Tree‐like classification in unsupervised clustering problems, where neither an a‐priori classification nor target‐attributes are known in advance. In the context of these two concepts, the current research contributes: (1) by expanding the saliency measure to all possible types of variables (nominal as well as numerical), (2) by evaluating, using five datasets, a composite model that combines the CBC method and the saliency concept. The findings show that by using clustering algorithms for classification tasks (CBC method) the results are as accurate as those obtained by conventional Decision Trees, but with a better saliency factor.     

Critical Elements Analysis of Water Supply Systems to Improve Energy Efficiency in Failure Scenarios

Water supply systems (WSS) are significant energy consumers, which makes it crucial to find methods to increase energy efficiency. A novel approach is presented here to locate and quantify the most vulnerable elements in terms of energetic efficiency. The method is based on a linear programming (LP) optimization model and the elimination of different components in the system to analyze their impact on energy costs. Pump reallocation is then suggested as a novel dynamic design paradigm for temporary changes in the system to cope with extreme scenarios. Exposing the critical components of WSS improves maintenance prioritization and inventory and contributes to the planning of future investments in the system. Pump reallocation provides an innovative approach for response to critical conditions, it is suggesting rethinking the design concepts to incorporate not just long-term solutions but also rapid, temporary steps in response to failures.

     

Pressure and gas composition effects on the operation of the pulsed flame photometric detector

The effect of pressure and hydrogen/oxygen ratio of a burning gas mixture on pulsed flame emission time-dependence was investigated in the range of 0.1–5 atm using a specially designed pulsed flame photometric detector (PFPD). We studied the pressure and gas composition effect on the pulsed flame delayed light emission of sulfur, phosphorus, and nitrogen-containing organic compounds. The optimal pressure conditions for nitrogen detection, intensity, and emission time delay was found to be 0.4 bar, at which the detection sensitivity could be improved by a factor of 2. For phosphorus, the optimal pressure obtained was 1.3 bar with 40% sensitivity improvement (compared with 1 bar). In the case of sulfur detection, two emission maxima were obtained, at 1.1 and 0.6 bar, at H/O ratio of 5. Increasing the H/O ratio resulted in the appearance of only one peak at 1 bar, and enhancement of the sensitivity by a factor of 2.4 at H/O ratio of 10.3. From the analytical point of view, we found that emission intensity is practically unchanged by the pressure and the H/O ratio for all three elements investigated in the range of 0.8–1.1 bar and H/O of 5–6. Thus, in addition to excellent sensitivity and improved selectivity, the PFPD can be applied under a variety of atmospheric pressure conditions in field environmental applications.     

A new parallelization strategy for solving time‐dependent 3D Maxwell equations using a high‐order accurate compact implicit scheme

With progress in computer technology there has been renewed interest in a time‐dependent approach to solving Maxwell equations. The commonly used Yee algorithm (an explicit central difference scheme for approximation of spatial derivatives coupled with the Leapfrog scheme for approximation of temporal derivatives) yields only a second‐order of accuracy. On the other hand, an increasing number of industrial applications, especially in optic and microwave technology, demands high‐order accurate numerical modelling. The standard way to increase accuracy of the finite difference scheme without increasing the differential stencil is to replace a 2nd‐order accurate explicit scheme for approximation of spatial derivatives with the 4th‐order accurate compact implicit scheme. In general, such a replacement requires additional memory resources and slows the computations. However, the curl‐based form of Maxwell equations allows us to construct an effective parallel algorithm with the alternating domain decomposition (ADD) minimizing the communication time. We present a new parallel approach to the solution of three‐dimensional time‐dependent Maxwell equations and provide a theoretical and experimental analysis of its performance. Copyright © 2006 John Wiley & Sons, Ltd.     

Fostering empowerment in online support groups

Online support groups have been used extensively, in numerous areas of distress, for 15 years. Researchers have presented conflicting findings and ideas about their effectiveness in helping people cope with respective problems. Our review of quantitative studies and our qualitative exploration of the nature of the experiences that occur in such groups show that several factors operate to potentially affect participants. Personal and interpersonal dynamics, which are central in producing effects in these groups, are induced and accelerated by the powerful online disinhibition effect. These factors, including the very impact of writing, expressions of emotions, collecting information and thereby improving understanding and knowledge, developing social relationships, and enhancing decision-making skills and consequent behavioral actions all serve as possible generators of a sense of personal empowerment for people in distress. This view may explain why empirical research has frequently found little or no specific outcomes from participating in online support groups; however, it has found much support for nonspecific personal impacts of this means of intervention. Thus, we contend that online support groups are designed to foster, and many of them actually do, well-being, a sense of control, self-confidence, feelings of more independence, social interactions, and improved feelings—all nonspecific but highly important psychological factors. As such, participating in an online support group could foster personal empowerment, which is much needed in handling specific conditions of distress. Nonetheless, this participation has potential costs, too, especially developing dependence, distancing from in-person contacts, and exposure to unpleasant experiences typical of social engagement in cyberspace.