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31.
Artificial immune systems can be applied to a variety of very different tasks including function optimization. There are even artificial immune systems tailored specifically for this task. In spite of their successful application there is little knowledge and hardly any theoretical investigation about how and why they perform well. Here rigorous analyses for a specific class of mutation operators introduced for function optimization called somatic contiguous hypermutation is presented. Different concrete instantiations of this operator are considered and shown to behave quite differently in general. While there are serious limitations to the performance of this type of operator even for simple optimization tasks it is proven that for some types of optimization problems it performs much better than standard bit mutations most often used in evolutionary algorithms. 相似文献
32.
Rusu C. van't Oever R. de Boer M.J. Jansen H.V. Berenschot J.W. Bennink M.L. Kanger J.S. de Grooth B.G. Elwenspoek M. Greve J. Brugger J. van den Berg A. 《Journal of microelectromechanical systems》2001,10(2):238-246
We have developed a micromachined flow cell consisting of a flow channel integrated with micropipettes. The flow cell is used in combination with an optical trap setup (optical tweezers) to study mechanical and structural properties of λ-DNA molecules. The flow cell was realized using silicon micromachining including the so-called buried channel technology to fabricate the micropipettes, the wet etching of glass to create the flow channel, and the powder blasting of glass to make the fluid connections. The volume of the flow cell is 2 μl. The pipettes have a length of 130 μm, a width of 5-10 μm, a round opening of 1 μm and can be processed with different shapes. Using this flow cell we stretched single molecules (λ-DNA) showing typical force-extension curves also found with conventional techniques. These pipettes can be also used for drug delivery, for injection of small gas bubbles into a liquid flow to monitor the streamlines, and for the mixing of liquids to study diffusion effects. The paper describes the design, the fabrication and testing of the flow cell 相似文献
33.
D. D. Zaitsev E. A. Gravchikova P. E. Kazin A. V. Garshev Yu. D. Tret’yakov M. Jansen 《Inorganic Materials》2006,42(3):326-330
Glasses with the nominal compositions SrFe12O19 + nNa2Sr2B4O9 (n = 4, 6, 8, 10) and SrFe12O19 + 6Na2Sr3B4O10 were prepared via rapid quenching of oxide melts and were then heat-treated between 500 and 800°C in order to produce glass-ceramics containing fine SrFe12O19 particles. The materials were characterized by x-ray diffraction, differential thermal analysis, electron microscopy, and magnetic measurements. The crystallization behavior of the glasses was investigated. The coercivity of the glass-ceramics was shown to increase with heat-treatment temperature, up to 486 kA/m. By dissolving the nonmagnetic matrix of the glass-ceramics with the nominal compositions SrFe12O19 + 6Na2Sr3B4O10 and SrFe12O19 + 4Na2Sr2B4O9, submicron-sized strontium hexaferrite particles were obtained. 相似文献
34.
D. D. Zaitsev P. E. Kazin A. V. Garshev Yu. D. Tret'yakov M. Jansen 《Inorganic Materials》2004,40(8):881-885
Glasses with nominal compositions of SrFe12O19 + 8SrB2O4 (I) and SrFe12O19 + 12Sr2B2O5 (II) are prepared by rapid quenching from the liquid state and are converted to glass-ceramics containing fine magnetic particles of SrFe12O19 by heat treatment between 600 and 950°C. The materials are characterized by x-ray diffraction, differential thermal analysis, electron microscopy, and magnetic measurements. The phase transformations accompanying glass crystallization are identified. The glass composition and heat-treatment conditions are shown to influence the aspect ratio of the forming submicron-sized strontium hexaferrite particles. The strongest coercive fields reached in glass-ceramics I and II are 504 and 456 kA/m, respectively. 相似文献
35.
Michael J. Dube Dennis Bollea William R. Jones Jr. Mario Marchetti Mark J. Jansen 《Tribology Letters》2003,14(1):3-8
Synthetic hydrocarbon liquid lubricants (based on polyalphaolefins) have been developed for use in space applications. These materials have been fully characterized and their physical properties reported which include: kinematic and absolute viscosity, viscosity index, vapor pressure, evaporation, specific gravity, pour point, coefficient of thermal expansion, refractive index, and flow activation energy. In addition, tribological properties under ultrahigh vacuum conditions have been determined. These include: lubricated lifetimes using a spiral orbit tribometer (SOT) and vacuum four-ball wear rates. These values are compared to existing state-of-the-art space lubricants. 相似文献
36.
Fatemeh Khodadust Aiarpi Ezdoglian Maarten M. Steinz Judy R. van Beijnum Gerben J. C. Zwezerijnen Gerrit Jansen Sander W. Tas Conny J. van der Laken 《International journal of molecular sciences》2022,23(13)
Extensive angiogenesis is a characteristic feature in the synovial tissue of rheumatoid arthritis (RA) from a very early stage of the disease onward and constitutes a crucial event for the development of the proliferative synovium. This process is markedly intensified in patients with prolonged disease duration, high disease activity, disease severity, and significant inflammatory cell infiltration. Angiogenesis is therefore an interesting target for the development of new therapeutic approaches as well as disease monitoring strategies in RA. To this end, nuclear imaging modalities represent valuable non-invasive tools that can selectively target molecular markers of angiogenesis and accurately and quantitatively track molecular changes in multiple joints simultaneously. This systematic review summarizes the imaging markers used for single photon emission computed tomography (SPECT) and/or positron emission tomography (PET) approaches, targeting pathways and mediators involved in synovial neo-angiogenesis in RA. 相似文献
37.
The development of digital libraries has enhanced the integration of textual and multimedia information in many document collections. The World Wide Web provides the connectivity for many digital library users. Studies exploring the searching characteristics of Web users are an important and a growing area of research. Most Web user studies have focused on general Web searching, regardless of subject matter or format. Little research has examined how Web users search for multimedia information. Our study examines users' multimedia searching on a major Web search service. The data set examined consisted of 1,025,908 queries from 211,058 users of Excite ®, a major Web search service. From this data set, we identified and analyzed queries for audio, image, and video queries. Our findings were compared to results from general Web searching studies. Implications for the design of Web searching services and interfaces are discussed. 相似文献
38.
Christian Clement Yde Jeroen Jasper Jansen Peter Kappel Theil Hanne Christine Bertram Knud Erik Bach Knudsen 《European Food Research and Technology》2012,235(5):939-949
In the present study, a novel method of measuring the uptake of nutrients by 1H NMR spectroscopy was performed to determine dietary effects. Six pigs catheterized in the portal vein and mesenteric artery were fed breads made from whole-wheat grain (WWG), wheat aleurone flour (WAF; 19?% aleurone of bread) or rye aleurone flour (RAF; 15?% aleurone of bread) in a repeated 3?×?3 crossover design. Three meals were provided daily (at 0, 5 and 10?h), and each period comprised of 1?week. Portal and arterial blood samples were collected at fasting (?30?min) on day 4–7, and on day 7, pooled blood samples were collected at 0–2.5, 2.5–5, 5–7.5 and 7.5–10?h after first (0?h) daily meal. Using the arterial-venous difference and ANOVA–simultaneous component analysis, plasma betaine was found to accumulate during the experimental period. On day 7, plasma betaine concentrations was 20–40?% higher than when feeding the WAF diet compared with RAF and WWG (P?=?0.001), whereas the content of betaine in the WAF diet was about twice as high. The arterial-venous difference showed a tendency (P?=?0.078) for the diet–time interaction of betaine absorption in the absorption phases but there was no diet effect (P?=?0.31), which indicates a steady-state absorption has been reached on day 7. Furthermore, high plasma betaine levels correlated with low plasma creatine of endogenous origin. In conclusion, the explorative method revealed that the plasma concentration and absorption of betaine were differentially modified by the diets. 相似文献
39.
D. Jansen J. Neubauer F. Goetz-Neunhoeffer R. Haerzschel W.-D. Hergeth 《Cement and Concrete Research》2012,42(2):327-332
The hydration process of a commercial Portland cement was followed by means of heat flow calorimetry. The measured heat flow was compared with calculated heat flow curves based on XRD data. Examined in particular was the influence of one selected superplasticizer on the hydration of the Portland cement. It was shown that the superplasticizer in question retards both the aluminate reaction and the silicate reaction. It is certainly conceivable that there are more than only one explanation for the interaction between the superplasticizer and the cement. A complexation of Ca2 + ions from pore solution by the superplasticizer is as thinkable as the adsorption of the polymer on the nuclei or the anhydrous grain surfaces which in turn might lead to the prevention of the growth of the nuclei or the dissolution of the anhydrous grains. 相似文献
40.
B. Bonnechère B. Jansen P. Salvia H. Bouzahouene V. Sholukha J. Cornelis 《Ergonomics》2014,57(4):622-631
The recent availability of the Kinect? sensor, a low-cost Markerless Motion Capture (MMC) system, could give new and interesting insights into ergonomics (e.g. the creation of a morphological database). Extensive validation of this system is still missing. The aim of the study was to determine if the Kinect? sensor can be used as an easy, cheap and fast tool to conduct morphology estimation. A total of 48 subjects were analysed using MMC. Results were compared with measurements obtained from a high-resolution stereophotogrammetric system, a marker-based system (MBS). Differences between MMC and MBS were found; however, these differences were systematically correlated and enabled regression equations to be obtained to correct MMC results. After correction, final results were in agreement with MBS data (p = 0.99). Results show that measurements were reproducible and precise after applying regression equations. Kinect? sensors-based systems therefore seem to be suitable for use as fast and reliable tools to estimate morphology.Practitioner Summary: The Kinect? sensor could eventually be used for fast morphology estimation as a body scanner. This paper presents an extensive validation of this device for anthropometric measurements in comparison to manual measurements and stereophotogrammetric devices. The accuracy is dependent on the segment studied but the reproducibility is excellent. 相似文献