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  • Springer  (62)
  • American Institute of Physics (AIP)  (3)
  • 2000-2004  (46)
  • 1975-1979  (19)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 53 (2000), S. 732-735 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  In the estimation of glycosidase activity by dinitrosalicylic acid (DNS) reagent, the stoichiometry of DNS reduction was reported to increase proportionately with the increase in the number of glycosidic linkages present in oligosaccharides liberated by the enzyme. The relationship between increases in DNS reduction and increases in the number of glycosidic bonds was found to be represented by a part of a rectangular hyperbola. The increase was optimum with disaccharide and insignificant when the degree of polymerization (DP) was ≥10. The difference did not arise as a result of the DNSA discriminating between mono- and oligosaccharide oxidation. The relationship stemmed from the acidity of the hydroxyl group adjacent to the reducing group, which repressed DNS reduction. The acidity is likely to decrease with an increase in oligosaccharide chain length. It is suggested that DNS reduction is actually optimum and uniform for all oligosaccharides of DP ≥ 10 and that it is minimum for monosaccharide. Thus the introduction of rectification factors in the estimation of glycosidase activities by the DNS method appears to be justified.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2000-06-13
    Print ISSN: 0175-7598
    Electronic ISSN: 1432-0614
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Springer
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 4670-4673 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A vacuum gauge has been designed and fabricated using a new type of sensor element, the semiconducting barium titanate positive temperature coefficient (PTC) thermistor. It covers a much wider range and better resolution compared to conventional Pirani gauge and other thermistor vacuum gauges particularly in the low vacuum levels due to its extreme high temperature coefficient. The details of design criteria of the instrument and its performance characteristics have been discussed. Due to the unique autocurrent limiting and stabilizing capabilities of a PTC thermistor, the fabrication of the instrument appears to be much cheaper. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 9201-9205 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We develop a method for measuring absolute two-photon absorption cross sections (σ2) and employ it to determine the σ2 of Rhodamine-6G in methanol (16.2±2.4 GM at 806 nm). Our measurement calibrates the relative excitation spectrum previously reported for this chromophore. The method is based on our derivation of an analytical expression describing the transmission of Gaussian laser pulses through a two-photon absorbing medium. The expression is valid for arbitrary absorber thickness, at all distances from the focus. This generalizes the prevalent "z-scan" (translation of the sample along the beam direction) technique for measuring two-photon absorbance, removing the requirements of a "thin" (thickness (very-much-less-than) Rayleigh range of the focused laser beam) sample and of placing the sample at the focus. This leads to an improvement of the sensitivity of the technique by over two orders of magnitude, enabling measurement of the two-photon absorption cross sections of even weakly absorbing specimens at moderate intensities. The results are significant for applications such as nonlinear microscopy, optical data storage and optical power limiting. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 2792-2795 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Moisture sensors based on porous alumina were designed and fabricated to detect and measure the concentration of moisture in gases. In the thin alumina disks taken, the surface and penetration effect has been considered during the process of adsorption and absorption of water molecules through pores and grain boundaries. Three different fabrication techniques, the tape casting technique, pelletization, and porous thick film, have been tried to achieve the desired moisture-sensing property of the samples. Different types of electrode structures and designs were also investigated and optimized to obtain maximum sensitivity. Electrodes were formed by screen printing the samples with thick film conductive pastes. The planar porous alumina sensor so obtained is found to be sensitive in the range of the 100–1000 ppmv level of moisture. The response time of the sensor in the ppmv range is approximately 2 min, and at higher concentrations of moisture it shows quasilinear dependency on the moisture content. © 2001 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Photonic network communications 2 (2000), S. 163-184 
    ISSN: 1572-8188
    Keywords: wavelength routed optical network ; dynamic lightpath assignment ; all-optical networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper, we have studied a number of algorithms for routing in all-optical wavelength routed networks. We have considered situations where a lightpath is dynamically created in response to a request for communication and the WDM channels constituting the lightpath are reclaimed when the communication is over. We have looked at two schemes for dynamic wavelength allocation. In the first scheme we have assumed the existence of a central agent to maintain a database of existing lightpaths where the central agent attempts to generate a new lightpath in response to a request for communication. In the second scheme, we attempt to generate a new lightpath using a distributed algorithm. In the first scheme we have exploited the existence of multiple paths between any pair of nodes in a network in order to reduce the blocking probability. For the second scheme, we have proposed three distributed strategies to determine, if possible, a lightpath when there is a request for communication. Each of these strategies have their advantages and disadvantages in terms of the expected blocking probability and the set-up time. We have studied the performances of both the schemes using Monte Carlo simulation.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Photonic network communications 2 (2000), S. 185-198 
    ISSN: 1572-8188
    Keywords: all-optical networks (AONs) ; WDM ; lightpath management ; optical layer protocol ; specification ; communicating finite state machine (CFSM) ; validation and reachability analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this work, we propose a control protocol for lightpath management in the optical layer of all-optical networks (AONs). AONs follow a layered structure, as used by various network standards, where each layer communicates with its peer through Protocol Data Units (PDUs). In the context of Open System Interconnection (OSI) Reference Model (RM), a new layer, called optical layer, has been introduced in the AON architecture to manage the lightpath related functions. The optical layer lies in between the physical layer and the data link layer. The objective of this paper is to define a specification for an optical layer protocol for managing lightpaths in AONs. In order to study the dynamics of the optical layer protocol system, we first employ the communicating finite state machine model to represent the protocol. Then a reachability analysis of the model is performed to verify the protocol. This paper shows how the optical layer protocol can be specified formally and made error-free by the step-wise refinement of an initial specification, where validation is done after each refinement.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Photonic network communications 2 (2000), S. 369-382 
    ISSN: 1572-8188
    Keywords: all-optical networks ; fault management ; distributed algorithm ; dynamic routing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper presents a distributed algorithm to determine fault avoiding routes between source-destination end-node pairs in an all-optical network. Fault-tolerant routing for WDM routed all-optical networks has not been studied in details in the literature except for using protection switching or loopback recovery. Such schemes use predetermined protection mechanism and hence assume that the protection path is not faulty. This paper considers extensions to a dynamic routing scheme (presented earlier by these authors for fault-free networks) to handle rerouting in case of fault occurrence. The performance degradations of the network because of fault occurrence are then studied in terms of blocking probability and set-up time through simulations.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Lifetime data analysis 6 (2000), S. 281-290 
    ISSN: 1572-9249
    Keywords: contamination model ; optimal tests ; Pivotal Parametric Product ; reliability distributions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Inferences on mixtures of probability distributions, in general,and of life distributions, in particular, are receiving considerableimportance in recent years. The likelihood ratio procedure oftesting for the null hypothesis of no contamination is oftenvery cumbersome and lacks its usual asymptotic properties. Recently,SenGupta (1991) has introduced the notion of an `L-optimal' testfor such testing problems. The idea is to recast the originalseveral parametric hypotheses representation of the null hypothesisin terms of only a single hypothesis involving an appropriatelychosen parametric function. This approach is shown to be bothmathematically elegant and operationally simple for a quite generalclass of mixture distributions which contains, in particular,all mixtures of the one-parameter exponential family and alsoa very rich subclass of mixtures useful in life-testing and reliabilityanalysis. It is also illustrated through two examples—onebased on real-life data and the other on a simulated sample.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of heuristics 6 (2000), S. 21-38 
    ISSN: 1572-9397
    Keywords: ATM networks ; dynamic routing ; PNNI ; simulations ; QoS ; multimedia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The goal of this paper is to recommend a good Private Network-to-Network Interface (PNNI) routing algorithm for private ATM networks. A good routing algorithm has to work well with multimedia traffic with several quality of service (QoS) requirements (such as cell loss ratio, cell delay and its variation etc.) in different networks under various traffic conditions. The multiplicity of QoS requirements makes the routing problem NP-complete, so our approach to the problem is based on large scale simulations involving several empirical algorithms (compliant with the PNNI routing specification) which have been tested for different network topologies and traffic scenarios. Based on analysis of tradeoffs involving performance metrics (such as blocking rate, complexity, load distribution) we recommend a consistently good routing algorithm for single domain ATM networks.
    Type of Medium: Electronic Resource
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