Jan Åke Jönsson

Static-priority scheduling on multiprocessors

The preemptive scheduling of systems of periodic tasks on a platform comprised of several identical processors is considered. A scheduling algorithm is proposed for static-priority scheduling of such systems; this algorithm is a simple extension of the uniprocessor rate-monotonic scheduling algorithm. It is proven that this algorithm successfully schedules any periodic task system with a worst-case utilization no more than a third the capacity of the multiprocessor platform. It is also shown that no static-priority multiprocessor scheduling algorithm (partitioned or global) can guarantee schedulability for a periodic task set with a utilization higher than one half the capacity of the multiprocessor platform.

Membrane-based techniques for sample enrichment.

Sample preparation techniques based on non-porous membrane extraction generally offer a high degree of selectivity and enrichment power, together with convenient possibilities for direct and automated connections to chromatographic and other analytical instruments. In this review principles and applications for techniques as supported liquid membrane extraction, microporous membrane liquid-liquid extraction, polymeric membrane extraction and membrane extraction with a sorbent interface are described and compared.

Memrane extraction in analytical chemistry

In this paper the principles and application of porous and non-porous membrane extraction techniques for sample preparation (pretreatment) in analytical chemistry are reviewed, with emphasis on aqueous samples of biological, environmental, or food origin. These techniques generally offer a high degree of selectivity and enrichment power, and also convenient possibilities for automated connections to chromatographic and other analytical instruments.

Liquid membrane extraction in analytical sample preparation: II. Applications

Abstract Membrane-based extraction techniques offer efficient alternatives to classical sample preparation techniques. In this review a number of examples from the fields of environmental and biomedical analysis are discussed. High selectivity and enrichment factors, as well as the possibility of automated interfacing to chromatographic and other analytical instruments, are shown for quantitative analysis.

Supported liquid membrane techniques for sample preparation and enrichment in environmental and biological analysis

Abstract Supported liquid membranes, mounted in a flow system can be used for selective and efficient extraction and enrichment of various types of analytes prior to gas or liquid chromatographic analysis. They can also be used for integrating field sampling. The basis of the technique is described, together with environmental (acidic herbicides, amines and metal ions) and biological applications (to amines).

Optimization of dispersive liquid-liquid microextraction of copper (II) by atomic absorption spectrometry as its oxinate chelate: Application to determination of copper in different water samples

In this study a dispersive liquid-liquid microextraction (DLLME) method based on the dispersion of an extraction solvent into aqueous phase in the presence of a dispersive solvent was investigated for the preconcentration of Cu(2+) ions. 8-Hydroxy quinoline was used as a chelating agent prior to extraction. Flame atomic absorption spectrometry using an acetylene-air flame was used for quantitation of the analyte after preconcentration. The effect of various experimental parameters on the extraction was investigated using two optimization methods, one variable at a time and central composite design. The experimental design was performed at five levels of the operating parameters. Nearly the same results for optimization were obtained using both methods: sample size 5 mL; volume of dispersive solvent 1.5 mL; dispersive solvent methanol; extracting solvent chloroform; extracting solvent volume 250 microL; 8-hydroxy quinoline concentration and salt amount do not affect significantly the extraction. Under the optimum conditions the calibration graph was linear over the range 50-2000 muicro L(-1). The relative standard deviation was 5.1% for six repeated determinations at a concentration of 500 microg L(-1). The limit of detection (S/N=3) was 3 microg L(-1).

Fixed-priority preemptive multiprocessor scheduling: to partition or not to partition

Traditional multiprocessor real-time scheduling partitions a task set and applies uniprocessor scheduling on each processor. By allowing a task to resume on another processor than the task was preempted on, some task sets can be scheduled where the partitioned method fails. We address fixed-priority preemptive scheduling of periodically arriving tasks on m equally powerful processors. We compare the performance of the best algorithms of the partitioned and non-partitioned method, from two different aspects. First, an average-case comparison, using an idealized architecture, shows that, if a system has a small number of processors, then the non-partitioned method offers higher performance than the partitioned method. Second, an average-case comparison, using a realistic architecture, shows that, for several combinations of preemption and migration costs, the non-partitioned method offers higher performance.

Mass transfer kinetics for analytical enrichment and sample preparation using supported liquid membranes in a flow system with stagnant acceptor liquid

Abstract Supported liquid membranes in a flow system have been utilized for selective sample enrichment, clean up and field sampling, prior to the application of chromatographic and spectrometric analytical methods. For similar objectives, supported liquid membranes may be combined with a number of other analytical systems. The technique has a wide range of applications, especially in the fields of enviromental analysis and bioanalysis. This paper presents the theoretical principles for the technique and the mass transfer kinetic equations relevant to most applications. Guidelines for the optimization of experimental conditions and physical dimensions of the extraction devices are discussed.

The utilization bounds of partitioned and pfair static-priority scheduling on multiprocessors are 50%

This paper studies preemptive static-priority scheduling on multiprocessors. We consider two approaches: global pfair static-priority scheduling and partitioned traditional static priority scheduling. We prove that if presented algorithms are used and if less than 50% of the capacity is used then all deadlines are met. It is known that no static-priority multiprocessor scheduling algorithm can achieve a utilization bound greater than 50%.

Concentration of amino acids using supported liquid membranes with di-2-ethylhexyl phosphoric acid as a carrier

Abstract Basic studies of a procedure for extraction of amino acids using a supported liquid membrane containing di-2-ethylhexyl phosphoric acid are presented. The extractions are made from an aqueous donor phase with pH 3 to a more acidic acceptor phase and the mass transfer is driven by the proton gradient between these phases. For 0.01 mM tryptophan and with 1 M HCl as acceptor phase, an extraction efficiency of 60% is obtained, constant up to at least 12 h. This permits concentration enrichment factors linearly increasing with time up to values of at least 150. For higher amino acid concentrations, the extraction efficiency is constant only over shorter time intervals.