bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐term survival and virus production in human primary macrophages infected by human immunodeficiency virus
Authors: Aquaro Stefano , Bagnarelli Patrizia , Guenci Tania , De Luca Andrea , Clementi Massimo , Balestra Emanuela , Caliò Raffaele , Perno Carlo‐Federico 
Published: October 2002

AbstractThe role of macrophages in the pathogenesis and progression of human immunodeficiency virus (HIV)‐related infection is substantiated by in vitro and in vivo evidence. The unique ability to survive HIV infection and produce viral particles for long periods is postulated. Detailed studies of this phenomenon are lacking. The dynamics of HIV‐1 replication and cumulative virus production was studied in long‐term cultures of macrophages in the presence or in the absence of antiviral drugs. Multiply spliced and unspliced HIV‐RNA production was assessed by quantitative PCR, and the number of infected cells was monitored by FACS analysis. Cumulative HIV‐1 production was determined by a trapezoidal equation, including such parameters as times of collection and experimental values of genomic‐RNA and p24 gag antigen. Unspliced and multiply spliced HIV‐RNA increased linearly after macrophage infection; reached levels of 1.5 × 108 and 2.8 × 105 copies/105 cells, respectively, at day 10; and then remained stable throughout the course of the experiment. Cumulative production of genomic‐RNA and p24 gag antigen was 1010 copies/106 cells and 107 pg/106 cells, respectively, with an average of >200 virus particles produced daily by each macrophage. AZT decreased the cumulative production of both genomic‐RNA and p24 gag antigen down to 2.5 × 109 copies and 1.1 × 106 pg/106 cells (73.8% and 88.9% inhibition, respectively) up to day 50 without virus breakthrough. Ritonavir had a limited, but consistent, efficacy on the release of mature virus proteins (about 40% inhibition), but not on HIV‐RNA production. In conclusion, the long‐term dynamics and the high cumulative virus production that characterize HIV‐1 infection of macrophages underscore the peculiar role of these cells as a persistently infected reservoir of HIV. J. Med. Virol. 68:479–488, 2002. © 2002 Wiley‐Liss, Inc.
Epithelial salivary glands neoplasms in children and adolescents: A forty‐four‐year experience
Authors: Ribeiro Karina de Cássia Braga , Kowalski Luiz Paulo , Saba Leda Maria Buazar , Camargo Beatriz de 
Published: October 2002

AbstractBackgroundEpithelial neoplasms of salivary gland origin are relatively uncommon in children and adolescents. Over a 44‐year period, there were 38 cases affecting children under 19 years of age in our Pediatric Hospital‐Based Tumor Registry.ProcedureMedical charts of 38 patients with epithelial neoplasms of salivary glands were reviewed. Data collected included demographic, clinical, and histological characteristics. Statistical analysis included descriptive statistics, Student t‐test, and Kaplan–Meier method was used for survival analysis.ResultsThe mean age was 11.8 years. There was a female preponderance of 1.9:1. The parotid gland was affected in most cases (65.8%). Twenty‐seven patients had malignant tumors and eleven patients presented benign neoplasms. Pleomorphic adenoma was the most frequent benign tumor (7 out of 11) and mucoepidermoid carcinoma was the most frequent malignancy (17 out of 27). Five‐year overall survival rate was 81.6% for patients with malignant tumors. Grade of differentiation was the only significant prognostic factor for patients with mucoepidermoid carcinomas.ConclusionsEpithelial salivary gland tumors are very rare in children. Surgery is the best option to achieve high cure rates and radiotherapy must have precise indications because of their long‐term side effects in young age. Med Pediatr Oncol 2002;39:594–600. © 2002 Wiley‐Liss, Inc.
Radical constructivism: Between realism and solipsism
Authors: Martínez‐Delgado Alberto 
Published: October 2002

AbstractThis paper criticizes radical constructivism of the Glasersfeld type, pointing out some contradictions between the declared radical principles and their theoretical and practical development. These contradictions manifest themselves in a frequent oscillation between solipsism and realism, despite constructivist claims to be an anti‐realist theory. The paper also points out the contradiction between the relativism of the radical constructivist principles and the constructivist exclusion of other epistemological or educational paradigms. It also disputes the originality and importance of the radical constructivist paradigm, suggesting the idea of an isomorphism between radical constructivist theory and contemplative realism. In addition, some pedagogical and scientific methodological aspects of the radical constructivist model are examined. Although radical constructivism claims to be a rational theory and advocates deductive thinking, it is argued that there is no logical deductive connection between the radical principles of constructivism and the radical constructivist ideas about scientific research and learning. The paper suggests the possibility of an ideological substratum in the construction and hegemonic success of subjective constructivism and, finally, briefly advances an alternative realist model to epistemological and educational radical constructivism. © 2002 Wiley Periodicals, Inc. Sci Ed 86:840–855, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10005
A simulation study of processing time dispatching rules
Authors: Fry Timothy D. , Philipoom Patrick R. , Blackstone John H. 
Published: October 2002

AbstractIn this paper, the performance of truncated variations of the shortest processing time (SI) dispatching rule was simulated in a ten machine job shop. Each of the truncated rules placed those jobs which had waited for a predetermined length of time into a secondary queue. As long as jobs existed in the secondary queue, they were given a higher priority than jobs waiting in the primary queue. Each of the truncated rules sequenced jobs from the primary queue by SI while sequencing from the secondary queue was by some other priority rule. The objective of the truncated SI rules was to improve upon the tardiness problem associated with the simple SI rule without worsening greatly the good performance of SI on job flowtimes. Results indicated that the truncated rules which sequenced jobs in the secondary queue by job slack achieved the desired results better than the rules which sequenced jobs from the secondary queue by processing time. However, it was found that the implementation of these rules is complicated by the variability in the percent of jobs sequenced from the secondary queue. A second class of truncated rules which are easy to implement is developed. The performance of these rules was found to be as good as other selected rules studied.
Case studies of computer integrated manufacturing systems: A view of uncertainty and innovation processes
Authors: Gerwin Donald , Tarondeau Jean Claude 
Published: October 2002

AbstractThe adoption and implementation of new manufacturing processes are conceptualized in terms of coping with uncertainty. Manufacturing management opts for new equipment in order to reduce certain long run, nagging uncertainties, but at the expense of introducing considerable short run uncertainty associated with the innovation. Various coping strategies must be employed to deal with the situation. Our ideas are explored and developed by comparing how four firms in different countries adopted and implemented computer integrated manufacturing systems (CIM). Qualitative interviews with managers at different hierarchical levels and in different functions brought answers to the following questions: 1) What were the reasons for adopting a CIM? 2) What strategies were employed in order to facilitate the introduction of CIM's into the Firm? 3) What were the significant implementation problems that were encountered? In spite of cultural and other differences among the firms, coping with uncertainty explains significant aspects of their innovation processes.
Safety stocks and component commonality
Authors: Baker Kenneth R. 
Published: October 2002

AbstractIn the implementation of an MRP‐based planning system it is often desirable to hold safety stocks at the component level. This approach is typical of a system that assembles finished products to order but builds components to a forecast. The same approach makes sense when end‐item buffers would be prohibitively expensive to maintain, or when there is significant spares demand for the components.The existing theory for sizing component safety stocks is little more than an application of the principles governing single‐level inventory decisions. The standard deviation of the distribution for demand is the key parameter. A multiple of this standard deviation, called the safety factor, is set by management policy. This safety factor determines the size of the safety stock. In simple cases there is a direct relationship between the safety factor and the level of customer service.Component commonality refers to a situation in which one component is common to more than one end item. The presence of commonality makes it difficult to determine safety stocks accurately. The existing theory, which is reviewed briefly, examines the effects of commonality on the component's safety factor. However, commonality destroys the relationship between safety factor and service level. This article introduces a simple example to illustrate this fact. The example suggests some problems that must be addressed if the theory is to encompass commonality. Among these are the need to develop service level measures for multiple products and to analyze the relationship between safety stock and service level.
Implementing multiple criteria ABC analysis
Authors: Flores Benito E. , Whybark D.Clay 
Published: October 2002

AbstractThis article presents the results of applying multicriteria ABC analysis to maintenance inventories. A large service organization and a consumer goods manufacturer participated in the study. The managers in both organizations used cost and noncost criteria for developing the ABC categories for inventory management. The study shows that managers can develop noncost criteria and classify the inventory items in ways that combine the criteria types. Specific policies were defined for managing the items in the industrial firm. Once the benefits of the methodology were demonstrated, a year‐long program for implementing the system was developed. The project is estimated to cost less than 10 to 15% of the available storeroom clerk manhours and provide substantially greater benefits.
A natural starting strategy for Aronson's heuristic 1 for solving the deterministic, single operator, multiple machine, multiple run cyclic scheduling
Authors: Aronson Jay E. 
Published: October 2002

AbstractThe semiautomatic nature of machinery often makes it economical to assign more than one machine to a single operator in a cyclic schedule. If the tasks, executed in a cyclic schedule, are not ordered properly, excessive interference can occur, even in deterministic problems. In a recent article [1], Aronson presented two efficient and effective heuristics for solving a more realistic generalization of the deterministic cyclic scheduling problem—one that has a single operator, multiple nonidentical machines, and multiple nonidentical runs on each machine.Here, the author supplies a natural strategy for initializing the first heuristic, because it is not satisfactory to run the heuristic many times, each time starting with a first run of a different machine, to obtain a reasonable solution. This modification is necessary to improve the performance of the heuristic, for ease of implementation, and savings of computational effort.An example problem is presented to compare the solution found using the heuristic with the new starting strategy to that of the heuristic using the original, random selection strategy. The solution found is optimal, whereas the original version of the heuristic obtained a solution within 8.1% of optimality.The new, natural starting strategy for the heuristic should improve its ability to solve problems with a single execution, and simplify its implementation on mainframes, minicomputers, and microcomputers. Increased use of the techniques outlined here should lead to a higher utilization of labor and machinery on the production floor.
Choosing optimal buffering strategies for dealing with uncertainty in MRP
Authors: Etienne Eisenhower C. 
Published: October 2002

AbstractDealing with uncertainty in the material requirements plan (MRP) is important, because of its importance in meeting the requirements of the master production schedule (MPS). In MRP, there is a critical need to make the MPS predictable and consistent.In the early days of MRP, a philosophy of zero safety stock or safety time was rigorously advocated. It was thought to be more advantageous to eliminate the need for buffering by freezing the MPS and managing lead times to make these firm. However, it was soon recognized that it is extremely difficult, in practice, to eliminate all uncertainty that affects the MPS and its execution. Practitioners know that some level of buffering is necessary (or inevitable) given the vicissitudes of the market place, production system planning and control, and supplier performance.This article accepts these premises and proposes a model and procedures for dealing with the buffering problem and choosing optimal buffering strategies in MRP.
Improved hierarchical production planning
Authors: Leong G.Keong , Oliff Michael D. , Markland Robert E. 
Published: October 2002

AbstractThis article addresses an overview of development and application of an integrated production planning model within the fiberglas industry. The system described represents a second generation in the development cycle of hierarchically based models within this batch production industry. A number of salient issues that distinguish this modeling approach from previous ones are examined.Our contention is that the explicit treatment and integration of demand forecasts within the context of production planning models is a necessary condition for implementation and ongoing use of such systems. Further, due to the nature of practical disaggregate problems, oft cited linear programming (LP) models will be set aside by more flexible goal programming solutions that explicitly recognize the dynamics of variations in product mix, production rates and management objectives. Finally, the development, delivery and maintenance of these planning models will increasingly be performed on microcomputer‐based systems and software versus traditional mainframes.
Job release and labor flexibility in a dual resource constrained job shop
Authors: Park Paul Sungchil , Bobrowski Paul M. 
Published: October 2002

AbstractMost of the past research in the area of job shop scheduling have used a model that simply equated job arrival with the release of the job to the shop floor for processing. Another common characteristic of this research is that it has ignored the worker altogether or confined the worker to a single type of machine. This study examines the role of labor flexibility in conjunction with the shop's ability to regulate the type and number of jobs active on the shop floor for processing. The release mechanisms that regulate the jobs on the shop floor consider both job and shop information in determining when a job should be released for processing. Labor flexibility, such as might be achieved through worker cross‐training, enables workers to operate more than one type of machine without any loss in productivity.Two release mechanisms with three levels of labor flexibility and two labor assignment rules are simulated in this study using two levels of job due date tightness. The shop performance is measured using several of the traditional measures as well as incremental and total cost. Results presented using statistical and graphical analysis show that there is no statistically significant difference in the performance using finite loading and infinite loading release mechanisms. Also, the inclusion of the minimum increment of labor flexibility produces the maximum performance improvement. Succeeding increases in labor flexibility show a diminishing return in shop performance.
An evaluation of order releasing and due date assignment heuristics in a cellular manufacturing system
Authors: Mahmoodi Farzad , Dooley Kevin J. , Starr Patrick J. 
Published: October 2002

AbstractThe presence of an order release function, where dispatchers can release or hold jobs from the first work center, has yielded beneficial results in practice but inconsistent results in research. Previous research results contradict the notion that shop floor information should be used to trigger the release mechanism. At the same time, such information has been effectively used to assign realistic due dates to released jobs.This study extends previous work on order releasing and due date assignment by providing a controlled comparison of three order releasing and two due date assignment heuristics in conjunction with six scheduling heuristics in a cellular manufacturing environment. Results show that controlled release deteriorates flow time, lateness, and tardiness performance and is inferior to both immediate and interval release. Controlled release appears to work best in situations of low load and tight due dates. Analysis of different dispatching rules shows the relative performance remains unchanged by the presence of different order release mechanisms.Comparisons of internally and externally set due date mechanisms indicate simpler, non‐due date oriented heuristics demonstrate as good a performance as the more complex due date oriented heuristics when shop information is utilized to assign job due dates. Finally, results indicate that in a manufacturing cell, the use of shop floor information is effective for due date assignment, but is not worthwhile for order releasing.
Production planning for mixed assembly/arborescent systems
Authors: Bookbinder James H. , Koch Leslie A. 
Published: October 2002

AbstractIn the automotive industry, components are fabricated from raw materials; modules from components; and subassemblies from modules. Final assembly of the end item, the vehicle, then follows. Such a process would be called an “assembly system” if each lower‐level entity (raw material, component. module) were used in only one immediate successor entity (component, module, subassembly).It is common to represent the bill of materials as a directed network. The nodes of this network are entities in the bill of materials; arcs in the network point from lower level entities in the direction of higher level entities and toward the end product. For example, if components 1 and 2 were combined to produce module a, there would be an arc from node 1 to node a. Similarly, there would be an arrow pointing from node 2 to node a.A pure assembly system may thus be described by saying that each node has at most one direct successor, although it may have several immediate predecessors. Similarly, a pure “arborescent network” is the prototype for a distribution system, whereby each node (say a warehouse) may have at most one immediate predecessor (distribution center), but possibly many immediate successors (retailers or smaller warehouses).The focus of this paper is that a complex manufacturing system often has arborescent or non‐assembly portions in its network. In automotive assembly, a given component frequently appears in more than one subassembly in the manufactured product. Certain components are used in each of four wheels; left‐ and right‐side body subassemblies contain common modules. The result is a mixed assembly/arborescent structure. Mixed assembly/arborescent structures also merit consideration as the prototype for combined production/distribution systems.In this article, we consider such mixed structures by building on properties of pure assembly and pure arborescent systems. First, for a wide class of parameters and various pure assembly structures, we study several single‐level lot‐sizing algorithms in conjunction with the cost‐parameter‐revision method of Blackburn and Millen (1982b). Cost‐parameter revision is a way to account for the impact at other stages, of decisions made at a given stage, in a pure assembly system. We also show it is better not to revise these cost parameters for a pure arborescent system.Our approach to a mixed assembly/arborescent system is thus based on identifying its “largest, independent pure assembly sub‐graph.” This is a significant subsystem of the original graph or network, the largest portion that is pure assembly in nature. Modification of the cost parameters there, followed by stage‐by‐stage application throughout the whole network of the best single‐stage lot‐sizing method, gives lower total costs than when no cost revision is applied in the mixed system. Suggestions are then made for further research.
Evaluating mixed‐model assembly line sequencing heuristics for just‐in‐time production systems
Authors: Sumichrast Robert T. , Russell Roberta S. 
Published: October 2002

AbstractWhen mixed‐model assembly lines use components fabricated in‐house, the demand for these components is not uniform over time and is affected by the sequence of models on the assembly line. Thus, without proper mixed‐model sequencing and the subsequent smoothing of component demand, the effectiveness of a just‐in‐time (JIT) production system is limited. This paper focuses on making component usage uniform. Five sequencing methods are reviewed, two suggested by Monden (1983) and used at Toyota (GC1 and GC2), and three proposed by Miltenburg (1989) (M‐A1, MA3H1, and M‐A3H2). Their performance is evaluated for the special case when all models use the same components. For all of the sequencing methods tested the mean absolute deviation of model usage varies directly with the number of models produced. There is no clear relationship between the mean absolute deviation of model usage and demand pattern or length of production sequence. Method M‐A3H2 produces the highest quality feasible solutions under all conditions tested. The relative performance of the methods does not appear to be related to the number of models, demand type, or length of production sequence.To compare methods for the more general case of different models requiring different components, a mixed integer programming (MIP) model is presented as a way to find an optimal sequence. The M1P creates optimal solutions but is too slow to be used in practice. The two goal chasing heuristics used by Toyota were considered on the basis of their ability to schedule production to use components linearly over time. It is shown that these methods differ widely in their ability to generate good sequences. The performance of both is best when the products assembled have simple product structures. When models require more than one of a given component or when models require many different components, the performance worsens. The difference in performance is very small for GC1, but significant for GC2.