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  • 1
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    Measures of Poor Early Growth Are Correlated with Lower Adult Levels of Thymosin-alpha1: Results from the Normative Aging Study (1988)
    Baltimore : Periodicals Archive Online (PAO)
    Human Biology. 60:3 (1988:June) 435 
    Details
    ISSN: 0018-7143
    Topics: Biology
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:5243-1988-060-03-000006
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  • 2
    Electronic Resource
    Electronic Resource
    Atmospheric equilibrium, instability and energy transport at the last glacial maximum (1996)
    Springer
    Climate dynamics 12 (1996), S. 497-511 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract. A range of diagnostics from two GCM simulations, one of the present-day climate and one of the last glacial maximum (LGM) is used to gain insight into their different temperature structures and eddy dynamics. There are large local increases in baroclinicity at the LGM, especially in the Atlantic storm track, with large accompanying increases in the low level transient eddy heat flux. However, the differences in the zonal mean are much smaller, and the increases in both baroclinicity and heat flux are confined to low levels. Supplementary experiments with baroclinic wave lifecycles confirm the marked contrast between local and zonal mean behaviour, but do not adequately explain the differences between the zonal mean climates. The total flux of energy across latitude circles in the Northern Hemisphere does not change much during DJF, although its transient component is actually reduced at the LGM (during JJA the transient component is increased). Calculations of total linear eddy diffusivity reveal that changes in the time mean stationary waves are chiefly responsible for the seasonal range of this quantity at the LGM, while they only account for half the seasonal range at the present-day.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820050123
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  • 3
    Electronic Resource
    Electronic Resource
    Atmospheric equilibrium, instability and energy transport at the last glacial maximum (1996)
    Springer
    Climate dynamics 12 (1996), S. 497-511 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A range of diagnostics from two GCM simulations, one of the present-day climate and one of the last glacial maximum (LGM) is used to gain insight into their different temperature structures and eddy dynamics. There are large local increases in baroclinicity at the LGM, especially in the Atlantic storm track, with large accompanying increases in the low level transient eddy heat flux. However, the differences in the zonal mean are much smaller, and the increases in both baroclinicity and heat flux are confined to low levels. Supplementary experiments with baroclinic wave lifecycles confirm the marked contrast between local and zonal mean behaviour, but do not adequately explain the differences between the zonal mean climates. The total flux of energy across latitude circles in the Northern Hemisphere does not change much during DJF, although its transient component is actually reduced at the LGM (during JJA the transient component is increased). Calculations of total linear eddy diffusivity reveal that changes in the time mean stationary waves are chiefly responsible for the seasonal range of this quantity at the LGM, while they only account for half the seasonal range at the present-day.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02346821
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  • 4
    Electronic Resource
    Electronic Resource
    Towards equitable distribution via proportional equity constraints (1993)
    Springer
    Mathematical programming 58 (1993), S. 287-294 
    Details
    ISSN: 1436-4646
    Keywords: Equitable distribution ; maximal flow algorithms ; knapsack problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We propose a new approach to the formulation of models for solving problems of equitable distribution. Equity is achieved by the use of “proportional equity constraints” which require that each recipient must receive ashare of the total distribution which falls within a prespecified range. The algorithmic implications of this new approach are illustrated using two mathematical models. We consider the problem of maximizing total flow in a multiterminal network with proportional equity constraints. An efficient algorithm for solving this problem is provided. As a further application, we show that the introduction of such constraints still permits easy solutions for the linear knapsack problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581272
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  • 5
    Electronic Resource
    Electronic Resource
    Pareto optimality and a class of set covering heuristics (1993)
    Springer
    Annals of operations research 43 (1993), S. 279-284 
    Details
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The set covering problem has many diverse applications to problems arising in crew scheduling, facility location and other business areas. Since the problem is known to be hard to solve optimally, a number of approximate (heuristic) approaches have been designed for it. These approaches (with one exception) divide into two main groups, greedy heuristics and dual saturation heuristics. We use the concept of a Pareto optimal dual solution to show that an arbitrary dual saturation heuristic has the same worst-case performance guarantee as the two best known heuristics of that type. Moreover, this poor performance level is always attainable by those two heuristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02025298
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  • 6
    Electronic Resource
    Electronic Resource
    Scheduling large robotic cells without buffers (1998)
    Springer
    Annals of operations research 76 (1998), S. 287-321 
    Details
    ISSN: 1572-9338
    Keywords: robotic cell, algorithms, computational complexity, traveling salesman problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract A robotic cell is a manufacturing system that is widely used in industry. A robotic cell contains two or more robot-served machines, repetitively producing a family of similar parts, in a steady state. There are no buffers at or between the machines. Both the robot move cycle and the sequence of parts to produce are chosen in order to minimize the cycle time needed to produce a given set of parts. This objective is also equivalent to throughput rate maximization. In practice, simple robot move cycles that produce one unit are preferred by industry. In an m machine cell for m 〉= 2, there are m! such cycles that are potentially optimal. Choosing any one of these cycles reduces the cycle time minimization problem to a unique part sequencing problem. We prove the following results in an m machine cell, for any m 〉= 2. The part sequencing problems associated with these robot move cycles are classified into the following categories: (i) sequence independent; (ii) capable of formulation as a traveling salesman problem (TSP), but polynomially solvable; (iii) capable of formulation as a TSP and unary NP-hard; and (iv) unary NP-hard, but not having TSP structure. As a consequence of this classification, we prove that the part sequencing problems associated with exactly 2m-2 of the m! available robot cycles are polynomially solvable. The remaining cycles have associated part sequencing problems which are unary NP-hard.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018952722784
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  • 7
    Electronic Resource
    Electronic Resource
    Design and operational issues in AGV-served manufacturing systems (1998)
    Springer
    Annals of operations research 76 (1998), S. 109-154 
    Details
    ISSN: 1572-9338
    Keywords: manufacturing, automated guided vehicles, design and operation, survey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract Automated Guided Vehicle (AGV) systems are already in widespread use and their importance for material handling is expected to grow rapidly. The advantages that such systems can offer include increased flexibility, better space utilization, improved factory floor safety, reduction in overall operating cost, and easier interface with other automated systems. This survey paper focuses on design and operational issues that arise in AGV systems. The objectives of the paper are to unify various lines of research related to AGVs and to suggest directions for future study. We consider problems arising in flowpath design, fleet sizing, job and vehicle scheduling, dispatching and conflict-free routing. Flowpath design problems address computationally intractable issues in the physical layout of a single loop and complex networks. Transportation and related models, waiting line analysis and simulation approaches are used to address fleet sizing questions. Scheduling issues focus on three flowpath layouts. In line layouts, the most important issues include finding an efficient job sequencing algorithm and identifying optimal AGV launch times. In loop layouts, issues such as joint scheduling of the job and AGV schedules, interface with a larger manufacturing system, dynamic job arrivals, and the location of the AGV parking area, are important. For complex network layouts, joint scheduling, heuristic dispatching rules, and conflict-free routing of AGVs, are considered. We identify the inefficiencies that result from addressing these issues in isolation, suggesting the need for integration. We also provide a summary of the most important open research issues related to all the above topics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018936219150
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  • 8
    Electronic Resource
    Electronic Resource
    Preemptive scheduling with finite capacity input buffers (1997)
    Springer
    Annals of operations research 70 (1997), S. 399-413 
    Details
    ISSN: 1572-9338
    Keywords: Preemptive single machine scheduling ; finite input buffers ; polynomial time algorithm ; NP-complete
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract In many scheduling problems, an arriving job is stored in an input buffer until it starts to be processed. Also, it may be necessary to hold a partially completed preempted job in an input buffer until processing of this job resumes. In the scheduling literature, most problems have been studied using the implicit assumption that the buffer has infinite capacity. We study preemptive single machine scheduling problems where the buffer capacity is finite. In this scheduling environment, jobs may be lost either because of insufficient input buffer capacity, or because due date requirements cannot be met. We examine problems where the objective is to minimize the weighted or unweighted number of lost jobs. Various assumptions about the generality of the data are examined. We present a complexity classification for various problems, either by deriving an efficient algorithm, or by proving that such an algorithm is unlikely to exist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018990625142
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  • 9
    Electronic Resource
    Electronic Resource
    Generalized preemption models for single-machine dynamic scheduling problems (1997)
    Springer
    IIE transactions 29 (1997), S. 359-372 
    Details
    ISSN: 1573-9724
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In the extensive scheduling literature, job preemption, if allowed, implies that the processing of a partly completed job is temporarily halted and later resumed at the same point. However, little attention has been given to problems where job preemption is allowed under the condition that either some startup time delay must be incurred or some fraction of work must be repeated if preemption occurs. We generalize the notion of job preemption by using models representing these conditions. The models are applied to studying the dynamic single-machine scheduling problems of minimizing total flow time, and of minimizing maximum lateness, subject to arbitrary and unknown job ready dates. On-line optimal dispatching rules, which consider only available – as opposed to look-ahead – information, are developed. These rules determine, on arrival or completion of each job, which available job should next be processed by the machine. A special case of our models, the preempt-repeat scenario, where preempted jobs must be totally repeated, is suggested as heuristic for the equivalent non-preemptive static problem where all ready dates are known and given. A computational study is performed to determine the potential benefits of reducing startup time delays or work repetition fractions in the context of continuous improvement of manufacturing systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018595801656
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  • 10
    Electronic Resource
    Electronic Resource
    Regulation of pituitary peptides by the immune system (1989)
    New York, NY : Wiley-Blackwell
    BioEssays 11 (1989), S. 141-144 
    Details
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: It has long been thought that the central nervous system is able to influence the progression of disease. Furthermore, there is now overwhelming evidence that the communication pathways are bidirectional. A variety of immune system peptides are now known to be capable of transmitting information from the immune system to the central nervous system. These immunotransmitters include interleukins, interferons and thymosine peptides which have the capability of modulating slow-wave sleep as well as the release of neuro- and pituitary peptides. In some instances, release of these peptides during early development may have long lasting, if not permanent effects upon the normal development of neuro-endocrine circuits. Collectively these various brain mediated events appear to contribute in various and diverse ways to defense against pathogens. It is becoming more and more apparent that certain abnormalities within the immune system may be the consequence of a neurological abnormality. The converse is also true.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bies.950110507
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