Unconstrained Inverse Electrocardiography: Epicardial Potentials

The inverse problem in electrocardiography is attacked via the development of a model appropriate for the computation of epicardial potentials from a knowledge of heart and torso geometry as well as surface potentials. The model takes the form of an integral equation of the first kind in which the kernel is interpreted as a Green's function. A theoretical investigation of system independence in the presence of error is developed, and two techniques for the theoretical consideration of system independence are examined. Application of these two techniques to concentric spherical systems indicates that spheres with ratios of inner-to-outer radii less than 0.5 contain less than twenty independent parameters in the presence of realistic noise levels. The number of independent parameters deteriorates rapidly as this ratio falls below 0.5. These results suggest that it is not feasible to determine epicardial potentials from torso potentials by using unconstrained solutions.     

Activities of the enzymes of hepatic gluconeogenesis in periparturient dairy cows with induced fatty liver

The objective was to measure the activities of all the enzymes essential for hepatic gluconeogenesis in dairy cows with induced fatty liver. We aimed to induce severe fatty liver in ten experimental cows by overfeeding them during the dry period while seven control cows were maintained on a restricted diet. To induce a marked negative energy balance, the experimental cows were deprived of feed for 8 h immediately after parturition. In addition, the experimental cows were given a restricted amount of diet during the first 5 d of lactation. Liver samples were collected 1 week before and 1, 2 and 4 weeks after parturition. Before parturition, liver triacylglycerol concentrations did not differ between the two groups. After parturition, the experimental cows developed marked fatty liver as indicated by a higher level of triacylglycerols in the liver compared with the control cows. Before parturition, all gluconeogenic enzymes in the liver were lower in experimental cows than in control cows. Phosphoenolpyruvate carboxykinase, pyruvate carboxylase and propionyl-CoA carboxylase were significantly lower and fructose 1,6-bisphosphatase and glucose 6-phosphatase tended to be lower in the experimental cows. The activities of two crucial enzymes for gluconeogenesis in ruminants, i.e., phosphoenolpyruvate carboxykinase and propionyl-CoA carboxylase, remained low throughout the sampling period post partum. Activities of pyruvate carboxylase and glucose 6-phosphatase in the experimental cows post partum were upgraded to values similar to those of the control cows. The results showed that the capacity for hepatic gluconeogenesis before parturition was lower in cows with induced fatty liver than in control cows. After parturition, the low activities of crucial gluconeogenic enzymes indicated insufficient production of glucose. It is suggested that the low gluconeogenic capacity leads successively to low blood glucose concentrations, low insulin levels and high rates of mobilization of fatty acid, causing severe hepatic lipidosis.     

Resonator stability subject to dynamic random-tilt aberration

We derive the behavior of the average exit time (i.e., the number of reflections before escape) of a ray path traveling between two perfect mirrors subject to dynamic random-tilt aberrations. Our calculation is performed in the paraxial approximation. When small random tilts are taken into account, we may consider an asymptotic regime that generically reduces the problem to the study of the exit time from an interval for a harmonic, frictionless oscillator driven by Gaussian white noise. Despite its apparent simplicity, the exact solution of this problem remains an open mathematical challenge, and we propose here a simple approximation scheme. For flat mirrors, the natural frequency of the oscillator vanishes, and, in this case, the average exit time is known exactly. It exhibits a 2/3 scaling-law behavior in terms of the variance of the random tilts. This behavior also follows from our approximation scheme, which establishes the consistency of the scaling law. Our mathematical results are confirmed with simulation experiments.     

An efficient infrastructure for native transactional XML processing

Implementation techniques for relational database management systems (DBMSs) have proven their efficiency and robustness in many existing systems. However, many of these concepts and mechanisms cannot be used when implementing a native XML DBMS (XDBMS) because of substantial differences in the processing properties of natively stored XML documents as compared to relational tables. Therefore, we have to develop new and appropriate techniques with ACID transaction guarantees tailored to the processing characteristics of tree documents and the operations on them.

For this reason, we want to provide for an efficient infrastructure of XDBMSs consisting of tree node addressing and indexing together with fine-grained locking of tree nodes. In this respect, our prime and novel contribution is to reveal the potential of our prefix-based node labeling called DeweyIDs supporting record addressing, indexing, and locking protocols. In this paper, we first sketch our version of prefix-based node labeling and summarize a quantitative study on them. An overview of our layered XDBMS architecture indicates the concepts and functionalities to be reused from relational DBMS implementations. The core part of the paper describes the infrastructural services for XML document storage with compressed DeweyIDs, the principles and methods for navigational and declarative processing of queries, as well as the lock modes and protocols to enable efficient collaboration. Selected empirical experiments evaluate the XTC system performance and support our system assessment.     

A brief history of mobile communication in Europe

Since the introduction of mobile telephony in the early 1950s in Europe, US and Japan the demand for this service exploded. It seems that the latent demand for mobile telecommunication services for decade’s continued to be very strong. After the introduction of cellular technology the capacity of the services became able to meet the massive demand. Next and future generations of mobile telecommunication technologies bring increased transmission speed and more versatile services. This forces network operators to organise multi sourced information flows supplied by service providers to increase the network effect of the system instead of providing the network infrastructure and leave the content to the users as in pure voice telephony. The drivers and inhibitors behind the emergence and recent developments of mobile telecommunications systems in Europe, are highlighted in this paper. Liberalisation of the telecom markets in Europe drove new entrants to the market and curbed excessive pricing. However, in recent years the lack of challenging service is the main cause for the wavering development of newer generations of mobile telecommunication services.     

CrimeSPOT: A language and runtime for developing active wireless sensor network applications

Advances in wireless sensing and actuation technology allow embedding significant amounts of application logic inside wireless sensor networks. Such active WSN applications are more autonomous, but are significantly more complex to implement. Event-based middleware lends itself to implementing these applications. It offers developers fine-grained control over how an individual node interacts with the other nodes of the network. However, this control comes at the cost of event handlers which lack composability and violate software engineering principles such as separation of concerns. In this paper, we present CrimeSPOT as a domain-specific language for programming WSN applications on top of event-driven middleware. Its node-centric features enable programming a node’s interactions through declarative rules rather than event handlers. Its network-centric features support reusing code within and among WSN applications. Unique to CrimeSPOT is its support for associating application-specific semantics with events that carry sensor readings. These preclude transposing existing approaches that address the shortcomings of event-based middleware to the domain of wireless sensor networks. We provide a comprehensive overview of the language and the implementation of its accompanying runtime. The latter comprises several extensions to the Rete forward chaining algorithm. We evaluate the expressiveness of the language and the overhead of its runtime using small, but representative active WSN applications.     

Technical and Environmental Sustainability Assessment of Water Distribution Systems

An environmental and technical sustainability assessment methodology is developed for both centralized and dual water distribution systems (WDSs) with and without fire flow scenarios. Technical sustainability of potable and reclaimed water networks is measured by a sustainability index (SI) assessment using reliability, resiliency, and vulnerability performance criteria. The U.S. Environmental Protection Agency EPANET software is used to simulate hydraulic (i.e. nodal pressure) and water quality (i.e. water age) analysis in a WDS. Total fresh water use and total energy intensity are considered as environmental sustainability criteria. The procedure considers two separate alternatives for meeting fire flows: (1) adding pumping to a system or (2) adding a non-potable WDS. The reclaimed system is designed using linear programming (LP) optimization. For each alternative, multi-criteria decision analysis (MCDA) is used to combine technical and environmental sustainability criteria for an urban WDS.     

Crystal Structure and Related Properties of Manganese-Doped Barium Titanate Ceramics

The influence of manganese on the crystallographic phase and the microstructure of BaTi_{1− x} Mn _x O₃ ceramics (0 ≤ x ≤ 0.05) is investigated. The crystal structure at room temperature changes from tetragonal to hexagonal between x = 0.005 and 0.017, which causes a drastic change in the microstructure. The Jahn_Teller distortion caused by the Mn_Ti³⁺ ions is proposed as the driving force for the phase transition. Annealing of the as-fired samples in both a reducing and oxidizing atmosphere restores the tetragonal phase, which is accompanied by a change in the microstructure based on the percentage of tetragonal phase.