Predictive and Adaptive Resource Reservation (PARR) for Cellular Networks

In cellular networks, a higher priority can, out of Quality of Service reasons, be given to ongoing connections than new call attempts. This can be achieved by having capacity in each cell (guard channels) exclusively reserved for arriving handover calls. In this paper, an advanced guard channel scheme, called Predictive and Adaptive Resource Reservation (PARR), will be introduced. The PARR scheme determines the amount of guard channels to allocate in a cell through subscriber movement predictions. The novelty of PARR is that both positioning and history-based measurements are used as input for the predictions. To improve the prediction accuracy, different data sets are applied for calls with different mobility and latest visited cells. Simulations will be used to show that significant performance improvements are obtainable with PARR.     

An efficient parameter extraction algorithm for MOS transistormodels

A general, direct parameter extraction algorithm that uses a small number of data points has been developed for MOS transistor models. This extraction algorithm has been tested using two transistor models in SPICE, MOS3, and BSIM. The basic idea of the algorithm is to use only one data point for each transistor parameter. Appropriate selection of the data points ensures physically reasonable values of most extracted parameters. Analytical expressions or rapidly converging numerical equations are used to calculate the parameters. Interaction between different parameters are taken into account. Good agreement between measured and simulated data is obtained from only 15 and 25 data points for MOS3 and BSIM, respectively. The total extraction time for a single transistor is around 40 s for MOS3 and 1 min for BSIM     

Microbial desulfurization of coal by Thiobacillus ferrooxidans and thermophilic archaea

Several different microorganisms have been suggested for coal desulfurization. In the present investigation, the thermophilic archaea Acidianus brierleyi (DSM 1651), Sulfolobus acidocaldarius (DSM 639) and Sulfolobus solfataricus (DSM 1616) were compared with the mesophilic bacterium Thiobacillus ferrooxidans (DSM 583) concerning their capability of removing sulfur from coal. The desulfurization rate as well as the amount of sulfur removed by the microorganisms was studied.

Two of the investigated microorganisms, Thiobacillus ferrooxidans and Acidianus brierleyi, were capable of oxidizing pure pyrite as well as oxidizing sulfur in coal. A kinetic analysis was performed assuming first order reactions. The rate constant for oxidation of pure pyrite by A. brierleyi was observed to be higher than for T. ferrooxidans. The values of the rate constants for sulfur removal from coal were comparable for the two microorganisms, but were higher than for oxidation of pure pyrite.     

A literature survey on traffic dispersion

Aggregation of resources is a means to improve performance and efficiency in statistically shared systems in general, and communication networks in particular. One approach to this is traffic dispersion, which means that the traffic from a source is spread over multiple paths and transmitted in parallel through the network. Traffic dispersion may help in utilizing network resources to their full potential, while providing quality-of-service guarantees. It is a topic gaining interest, and much work has been done in the field. The results are, however, difficult to find, since the technique appears under many different labels. This article is therefore an attempt to gather and report on the work done on traffic dispersion in communication networks. It looks at a specific instance of this general method. The processes are communication processes, and the resource is the link capacity in a packet switched network     

BIACORE analysis of histidine-tagged proteins using a chelating NTA sensor chip

While BIACORE instruments are routinely used for kinetic measurements and for the determination of binding constants, the immobilization of a ligand onto the sensor chip surface has to be individually optimized for every system. We show here that the histidine (His) tag, routinely used in protein purification and in detection is an ideal tag for immobilization, despite the intrinsically low affinity between an immobilized metal ion and the His tag. This is due to strong rebinding effects caused by the high surface density of immobilized Ni2+-nitrilotriacetic acid (NTA) on the chips used here. The immobilization of the ligand can be adjusted to a low level using the same chip, such that mass transport limitation and rebinding of the analyte to the immobilized ligand is minimal. Nine different proteins with different numbers of His tags were tested for stable binding to the Ni2+-NTA surface. Most proteins with one His tag dissociate very rapidly from the Ni2+-NTA surface, and the KD for the interaction between His tag and Ni2+-NTA was estimated to about 10(-6) m at neutral pH. In contrast, two His tags are usually found to be sufficient for stable binding. The kinetics of the chaperonin system of Escherichia coli GroEL and GroES were analyzed as a model using this system and found to be very similar to those obtained with covalently immobilized ligands. The sensor chip can be reused many times, because of the powerful regeneration methods. The ligand can be freshly immobilized after each cycle, thus eliminating potential denaturation upon regeneration as a source of error.     

Costs and effects of microsurgery versus radiosurgery in treating acoustic neuroma

This study analyses costs and effects of treating acoustic neuroma patients by using microsurgery compared to radiosurgery. Radiosurgery is the stereotactic application of radiotherapy and an innovative medical technology. Cost and effect estimates of conventional treatment were based on a retrospective study in the Netherlands. Similar data for a comparable group of patients in Sweden were collected for radiosurgery, as this treatment option is currently not available in the Netherlands. Fifty-three acoustic neuroma patients who had been operated on the University Hospital Rotterdam between November 1990 and February 1995 were included. This group was compared with 92 acoustic neuroma patients treated with radiosurgery (Gamma Knife. Stockholm, Sweden) in the same period. Data on health care use were collected from patient files. To obtain data on production losses and quality of life, a questionnaire was sent by mail in February 1995. This booklet consisted of the Health and Labour-questionnaire (HLQ), the Short Form-36 (SF36) and the EuroQol. The response rate was 92%. Direct costs for microsurgery amounted to Dfl. 20.072,- and for radiosurgery to Dfl. 14.272,-. Indirect costs were respectively Dfl. 16.400,- and Dfl. 1.020,-. General health rating was better for radiosurgery than for microsurgery. On the whole, differences in clinical outcomes between the two patient groups were small. Assuming a reasonable occupancy rate of the expensive radiosurgery equipment, we demonstrated that for the short term treating patients with acoustic neuroma with an extra-meatal tumour diameter of less than 3 centimeters, radiosurgery is more cost-effective than microsurgery.     

Fiber optical parametric amplifier pulse source: theory and experiments

An evaluation of a fiber optical parametric amplifier (FOPA)-based pulse source in terms of pulse width and chirp is presented. Experiments are performed when operating the FOPA as a pulse source, requiring a sinusoidally modulated pump. The FOPA is generating pulses at 10 GHz, and are measured using a streak camera capable of measuring pulses as a function of time, wavelength, and intensity. Experimental results are presented together with a theory for chirp and pulse widths that show good agreement.     

Schooling space: where South Africans learnt to position themselves within the hierarchy of apartheid society

In setting out to understand how South African school space was harnessed to the political project of apartheid, the author explores memory accounts from several adults who attended school during the apartheid era. Her analysis of their reminiscences found that non-pedagogic areas of the school and public domain beyond school premises were places where learners encountered their Other. Those sites provided the conditions for poignant awakenings to racialised identifications within discriminatory hierarchies. The article ends with the author reflecting on the effectiveness of spatially segregated schooling, when she works towards understanding her informants' uncritical tributes to the educational and moral value of their apartheid-era schooling.     

Bioactive double glass coatings for Co-Cr-Mo alloy

Glass compositions for double coatings for a Co-Cr-Mo alloy were developed. The glass compositions were chosen to fulfil such requirements as matching thermal expansion, low glass transition temperature and moderate solubility. For the ground coat a fairly high durability is required, whereas the cover coat must be bioactive, i.e. become attached to living bone by a chemical bond. Two compositions of each type were developed by computer-aided optimization. The glasses were chosen in the Na₂O–CaO–B₂O₃–Al₂O₃–SiO₂–P₂O₅ system. The bioactivity was tested in vitro by immersion in a simulated body fluid. The double coatings on Co–Cr–Mo alloy released hexavalent chromium into the solution as detected by yellow colouration and spectrophotometry. This colouration was strong at the margin between coated and uncoated metal and may be explained by oxidation of trivalent chromium of the alloy in the presence of glass. The released chromium did not have any notable effect on the calcium phosphate formation. After replensihing the solution no coloration was observed. This suggests that the chromate is easily dissolved and that it may be possible to wash it out prior to implantation.