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  • Springer  (70)
  • Public Library of Science (PLoS)
  • 2000-2004  (58)
  • 1965-1969  (12)
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  • 1
    Electronic Resource
    Electronic Resource
    A deadlock model for a multi‐service medium access protocol employing multi‐slot N‐ary stack algorithm (msSTART) (2000)
    Springer
    Wireless networks 6 (2000), S. 391-399 
    Details
    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract Many modern multi‐service medium access protocols (MACs) use a collision based capacity request signaling channel as part of a hybrid TDMA frame structure. Multi‐slot Stack Random Access Algorithm (msSTART) is proposed for use in IEEE 802.14 hybrid fiber/coaxial network and will be highly relevant for the S‐MAC development of evolving WATM MAC specifications. This paper studies the performance of msSTART as an example of a Q‐ary tree contention resolution algorithm (CRA) in the wireless environment using the novel Basic Deadlock model. We contrast approximate results for msSTART performance obtained by simulation under extreme inter‐station correlation with analytical results for the more popular p‐persistence CRA used in several testbed WATM implementations. Using three signaling channel schemes designed to provide support for increased system stability, to implement priority in the wireless MAC, and maximise efficiency, we provide comparative results for evaluation of msSTART and p‐persistence ALOHA under what the IEEE 802.14 working group has termed the “disaster scenario”. We find that of the three schemes evaluated the full Contention Mini‐Slot (CMS) sharing scheme employing multiple CMSs per data region extends the protocol's useable load region the furthest. We conclude that Q‐ary tree contention resolution algorithms (in particular msSTART) are best adapted to the wireless environment, providing less case sensitive performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019122522053
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  • 2
    Electronic Resource
    Electronic Resource
    High-spin structure of $N\simeq Z$ nuclei around the A = 72 region (2003)
    Springer
    The European physical journal 20 (2003), S. 131-132 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. High-spin states have been studied in 72Kr and 72Br using the 40 Ca + 40 Ca and 36 Ar + 40 Ca reactions at 164 and 145 MeV, respectively. The properties and configurations of the high-spin bands observed have been interpreted using unpaired cranked Nilsson-Strutinsky (CNS), and for 72Kr, paired cranked relativistic Hartree-Bogoliubov (CRHB) calculations. In 72Kr a new band has been identified that has the properties expected for the doubly aligned S-band configuration. In 72Br the previously known bands have been extended to higher spin. This has lead to a re-interpretation of the configurations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epja/i2002-10338-7
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  • 3
    Electronic Resource
    Electronic Resource
    Computers and Resource-Based History Teaching:A UK Perspective (2000)
    Springer
    Computers and the humanities 34 (2000), S. 325-343 
    Details
    ISSN: 1572-8412
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Media Resources and Communication Sciences, Journalism
    Notes: Abstract This article presents an overview of developments incomputer-aided history teaching in higher education inthe UK and the US, which have focused primarily onproviding students with access to primary sources inorder to enhance their understanding of historicalmethods and content. From an initial emphasis onresearch training for postgraduates, which taughtquantitative methods, or the use of drill-stylequestion-and-answer programs, advances in hardwarecapacity and software provision have led to morevaried methods of analysis. Computer-assisted learninglends itself particularly to the growing emphasis onstudents' use of primary sources, as more texts becomeavailable in electronic format on CD-ROM or the WorldWide Web. Hypermedia can provide a unique learningenvironment in which students are exposed to differentgenres of sources such as images, texts and numericaldata, encouraging them to discover interconnectionsand complexities, while learning at their own pace.Students can be expected to develop critical skills bycomparing primary sources and forming their ownhistorical interpretations. The various problems andmethods of locating and assessing relevant informationin cyberspace also foster critical thinking and aspirit of investigation. A computer-assisted coursetaught in Glasgow showed that students value the easeof access to relevant source materials offered bycustomised resource packs, which left them with moretime to evaluate their contents critically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1002448312963
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of three contrasting onion (Allium cepa L.) production systems on nitrous oxide emissions from soil (2000)
    Springer
    Biology and fertility of soils 31 (2000), S. 334-342 
    Details
    ISSN: 1432-0789
    Keywords: Key words Nitrous oxide ; Clover ; Herb ley ; Soil pH ; Allium cepa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  N2O emissions were measured from three contrasting onion (Allium cepa L.) production systems over an 8.5-month period. One system was established on soil where a clover sward had 3 months earlier been ploughed in (ploughed clover site). This production system followed conventional production management practices. The other two systems were established on soil where a mixed herb ley had 3 months earlier been either ploughed or rotovated. These last two production systems followed the guidelines of the International Federation of Organic Agriculture Movements (IFOAM). Cumulative N2O emissions were significantly greater from the ploughed clover site compared to the ploughed ley site (3.8 and 1.6 kg N2O-N ha–1, respectively), while cumulative N2O emissions from the ploughed ley and rotovated ley sites were not significantly different from each other. Emissions from all sites were dominated by episodes of high N2O flux activity following seedbed preparation and drilling, when soil water suction (SWS) was shown to be the rate-controlling variable. The decline in the N2O fluxes after these peak emissions followed clear exponential relationships of the form F=Ae– kt (r≥0.91), where F is the daily flux and A is the y-intercept. First-order decay constants (k) during these periods of declining N2O fluxes (corresponding to half-lives of 2.6–3.0 days) were not significantly different in magnitude from the first-order rate constants that characterised the increasing SWS. Gross differences in cumulative emissions between the clover and ley sites were attributed to the influence of differing soil pHs at the two sites on the N2O:(N2O+N2) ratio in the denitrification products. It also appeared that fertiliser applications to the clover site had both direct and indirect effects on N2O emissions by: (1) enhancing N2O emissions via potential nitrification, (2) increasing the NO3 – supply for enhanced N2O emissions via denitrification, and (3) influencing the N2O:(N2O+N2) ratio by lowering soil pH and increasing NO3 – concentrations. Onion crop yields were greater at the clover site, mainly due to the higher density of planting made possible under a conventional production philosophy. Expressing the yield on the basis of net N2O emissions, 23 t onions kg–1 N2O-N was obtained from the ploughed clover, which was double that obtained for the two systems based on the ley site. However, when the N2O emissions from the cultivation of the soils prior to the sowing of the onions was included, all three systems produced a similar yield per kilogram of N2O-N emitted, averaging 10 t kg–1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050665
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  • 5
    Electronic Resource
    Electronic Resource
    Release of sulphate-sulphur, potassium, calcium and magnesium from spent mushroom compost under field conditions (2000)
    Springer
    Biology and fertility of soils 31 (2000), S. 128-133 
    Details
    ISSN: 1432-0789
    Keywords: Key words Spent mushroom compost ; Soil ; Lysimeter ; Nutrient release ; Kinetic models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The release of SO4 2–-S, K+, Ca2+ and Mg2+ from soil amended with spent mushroom compost (SMC), a byproduct of mushroom production, was measured in leachate from field lysimeters for 30 weeks. Rates of application were 0 and 80 t ha–1 moist SMC. The SMC contained 1.7% K, 6.5% Ca, 0.4% Mg and 1.2% S (of which 87% is SO4 2–-S), and has a C : S ratio of 26. The break-through curves of ion leaching were polymodal indicating the preservation of soil structure in the lysimeters and its influence on leaching. SO4 2–-S release from SMC was rapid (first-order exponential) and was very similar to the release from a laboratory incubation. The release of K+, Ca2+ and Mg2+ was described using first/zero-order models which were also used to describe their release in the laboratory. The rate and amount of Ca2+ release was similar in the field and laboratory, but the amount of K+ (and to a lesser extent Mg2+) release was less in the field than in the laboratory. Recoveries of SMC applied nutrients in leachate were 80% of S (263 kg ha–1), 3% of K (14 kg ha–1), 16% of Ca (284 kg ha–1) and 37% of Mg (40 kg ha–1). Little if any S was mineralised. Using SMC could provide plants with S, K, Ca and Mg but there is potential for SO4 2–-S losses via leaching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050635
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  • 6
    Electronic Resource
    Electronic Resource
    Enzymology of Phanerochaete chrysosporium with respect to the degradation of recalcitrant compounds and xenobiotics (2000)
    Springer
    Applied microbiology and biotechnology 54 (2000), S. 751-758 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The archetypal white-rot fungus Phanerochaete chrysosporium has been shown to degrade a variety of persistent environmental pollutants. Many of the enzymes responsible for pollutant degradation, which are normally involved in the degradation of wood, are extracellular. Thus, P. chrysosporium is able to degrade toxic or insoluble chemicals more efficiently than other microorganisms. P. chrysosporium has a range of oxidative and reductive mechanisms and uses highly reactive, nonspecific redox mediators which increase the number of chemicals that can be effectively degraded. This review gives an overview of the enzymes that are believed to be important for bioremediation and briefly discusses the degradation of some individual chemicals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530000459
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  • 7
    Electronic Resource
    Electronic Resource
    Glutathione-mediated mineralization of 14C-labeled 2-amino-4,6-dinitrotoluene by manganese-dependent peroxidase H5 from the white-rot fungus Phanerochaete chrysosporium (2000)
    Springer
    Applied microbiology and biotechnology 54 (2000), S. 659-664 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Manganese-dependent peroxidase (MnP) H5 from the white-rot fungus Phanerochaete chrysosporium, in the presence of either Mn(II) (10 mM) or GSH (10 mM), was able to mineralize 14C-U-ring-labeled 2-amino-4,6-dinitrotoluene (2-A-4,6-DNT) up to 29% in 12 days. When both Mn(II) and GSH were present, the mineralization extent reached 82%. On the other hand, no significant mineralization was observed in the absence of both Mn(II) and GSH, suggesting the requirement of a mediator [either Mn(II) or GSH] for the degradation of 2-A-4,6-DNT by MnP. Using electron spin resonance (ESR) techniques, it was found that the glutathionyl free radical (GS•) was produced through the oxidation of GSH by MnP in the presence as well as in the absence of Mn(II). GS• was also generated through the direct oxidation of GSH by Mn(III). Our results strongly suggest the involvement of GS• in the GSH-mediated mineralization of 2-A-4,6-DNT by MnP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530000436
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  • 8
    Electronic Resource
    Electronic Resource
    Lifestyle Factors Affecting Bone Ultrasonometry of the Calcaneus in Japanese Women (2000)
    Springer
    Calcified tissue international 66 (2000), S. 43-46 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Densitometry — Calcaneus — Lifestyle — Exercise — Calcium intake.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract: Ultrasonometry is increasingly used to assess bone characteristics. A group of 1412 women with a mean age of 57 years attended a screening examination in a Japanese city. Seventy-four percent of participants were postmenopausal. Broadband ultrasound attenuation (BUA), speed of sound (SOS), and Stiffness index (SI) of the calcaneus were measured; subjects also completed a questionnaire examining lifestyle factors; anthropometric data were recorded. Analysis showed that the strongest predictors of decreased BUA, SOS, and SI were increased age and menopausal status. Higher body mass index and current participation in exercise or sports were significant predictors of increased BUA, SOS, and SI in a multivariate model. Higher calcium intake predicted increased BUA (P= 0.004) and missing meals predicted a lower SOS (P= 0.019). This study suggests that dietary factors as well as physical activity influence bone characteristics assessed by QUS. QUS may be a suitable technique to assess the effect of lifestyle changes on bone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002230050008
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  • 9
    Electronic Resource
    Electronic Resource
    Sucrose utilization during potato microtuber growth in bioreactors (2000)
    Springer
    Plant cell reports 19 (2000), S. 407-413 
    Details
    ISSN: 1432-203X
    Keywords: Key words Solanum tuberosum L. ; In vitro tuberization ; Micropropagation ; Invertase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Potato microtubers are used as pathogen-tested in vitro stocks for certified seed potato production. Microtubers grown in a rotating bioreactor grew at a faster rate when the medium was replaced frequently. Although the total microtuber number was not affected, the number of microtubers over 1 g quadrupled when 75% of the medium was replaced every 2 weeks when compared with no medium refreshment. Significantly slower microtuber growth rates resulted when a lower sugar concentration (40 g 1−1 instead of 80 g 1−1) was used or when a mixture of glucose and fructose replaced sucrose. Although high sucrose levels are necessary for optimal microtuber production, the sucrose supplied was rapidly hydrolyzed into glucose and fructose, making the long-term maintenance of desirable sucrose levels difficult. These results indicate that successful strategies to reduce sucrose hydrolysis without inhibiting microtuber growth will improve the efficiency of sucrose utilization in potato microtuber bioreactors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990050748
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of hyperons on the vibrations of neutron stars (1969)
    Springer
    Astrophysics and space science 5 (1969), S. 213-253 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We calculate the effects of hyperons and resonance particles on the vibrations of neutron stars. Vibrating neutron stars can store large amounts of energy in their vibrations; the interaction of the vibrations with the atmosphere would produce electromagnetic radiation. If any process damps out the vibrations rapidly on an astronomical time scale (∼ 1000 years) then vibrating neutron stars are not likely to be found. Previous work indicates that radiation by a neutrino URCA process (N+N→P+N+e −+ $$\bar v_3 $$ ) does not rapidly damp many of the neutron star models. Some neutron stars are predicted to contain massive baryons; here we study thermal damping by nonequilibrium reactions involving these baryons. During vibrations the thermodynamic equilibrium state is changed and particle reactions attempt to restore equilibrium. If the reaction rates per particle are very rapid or slow compared to the frequency of vibration the system follows almost the same pressure-volume curve through both parts of the gas cycle, and very little work is done. In the intermediate case, when reaction rates are comparable to the frequency, damping is rapid. We find that the reaction rates for weak interactions such asN+N↔P+Σ− (the Σ− is the first hyperon to appear with increasing density in degenerate neutron star matter) are of the right magnitude to cause rapid damping. If there is a hyperon region in the star then it cannot sustain vibrations. We also consider the much faster (and hence less important) processN+N↔P+Δ−.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00650292
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