Use of tunable nanopore blockade rates to investigate colloidal dispersions.

Tunable nanopores fabricated in elastomeric membranes have been used to study the dependence of ionic current blockade rate on the concentration and electrophoretic mobility of particles in aqueous suspensions. A range of nanoparticle sizes, materials and surface functionalities has been tested. Using pressure-driven flow through a pore, the blockade rate for 100 nm carboxylated polystyrene particles was found to be linearly proportional to both transmembrane pressure (between 0 and 1.8 kPa) and particle concentration (between 7 × 10(8) and 4.5 × 10(10) ml( - 1)). This result can be accurately modelled using Nernst-Planck transport theory, enabling measurement of particle concentrations. Using only an applied potential across a pore, the blockade rates for carboxylic acid and amine coated 500 and 200 nm silica particles were found to correspond to changes in their mobility as a function of the solution pH. Scanning electron microscopy and confocal microscopy have been used to visualize changes in the tunable nanopore geometry in three dimensions as a function of applied mechanical strain. The pores were conical in shape, and changes in pore size were consistent with ionic current measurements. A zone of inelastic deformation adjacent to the pore has been identified as important in the tuning process.

Integration of information systems: assessing its quality.

Due to organizational and technological changes the need for integrating information systems within healthcare institutions, has increased enormously. Although the technical means for systems integration have definitely matured, integration methodologies are still in their infancy. Two important questions regarding systems integration are hardly ever addressed in a systematic way: how to derive integration requirements, and how to check whether the requirements are met in a given integrated system. These two questions must be answered if we want to assess or improve the quality of integration of a given set of systems. In this article we present a nine-step method for deriving integration requirements from a business process model, and we assess the quality of integration of a given integrated system against these requirements. The method is demonstrated by elaborating two case studies from the health care domain.

Constructing an enterprise viewpoint: evaluation of four business modelling techniques.

Business process modelling is presented as an important first step in the process of designing a distributed system by integrating pre-existing components. The elements describing a business process are derived from the ODP-enterprise viewpoint language. One of the viewpoints distinguished in the Open Distributed Processing standard is the enterprise viewpoint. This viewpoint describes the organizational context in which the distributed system to be constructed will be used. In this paper we will review four business modelling techniques and their suitability for expressing the enterprise viewpoint is evaluated.

Integrating information systems in medicine: a reference model for middleware.

This paper addresses the problem of integrating healthcare information systems, from a technological viewpoint. We propose to take the concept of an ¿integration service' as an elementary concept in discussing the problem of integration. We then propose a taxonomy for grouping integration services according to their functionality and their domain specificity. The use of this taxonomy for decomposing an integration problem into (less complex) sub-problems is demonstrated. Finally, a sequence of steps to be taken in solving an integration problem is discussed.

Picture archiving and communication system design issues: the importance of modelling and simulation.

Picture archiving communication system (PACS) development turns out to be very complex. Due to both the vast amount of data and the complexity of hospital organizations, currently only small-scale systems have been realized. And although the experiences obtained with these systems are essential, there is a risk for underestimating the complexity and requirements inherent in hospital-wide PACS systems. In this paper, it is advocated that modelling and simulation be used as tools to obtain insight into the behavior and structure of future PACS systems. Modelling and simulation can also be used to actively support the design of PACS, especially its software. In order to capture the full complexity of PACS in a simulation model, and to take full advantage of simulation as a design tool, the development of a new modelling method has begun. This method is based on semantic data models and decision processes, and can be used for both system analysis and design. The first systems modelled with this method were imaging procedures in a hospital and a computer network. The resulting simulation models are a direct reflection of reality, and have a high degree of modularity. Consequently, in spite of the complexity of the systems, their models are easy to understand and maintain.