bluuebunny/crossref_metadata_2025 huggingface dataset:
Possible Changes in Logistic Chain Relationships Due to Internet Developments
Authors: Bollo D. , Stumm M.
Published: August 2006

For many years EDI was considered as costly but excellent for quick and safe exchange of trade information in freight transport operations. Today Internet settlement suggests different business possibilities, in many ways complementary to EDI. For the last couple of years, we can observe that thr Internet is becoming a pervasive technique. Large transport firms are now have a presence on the WEB, and propose direct services through this media. Also most of them use Intranet for their electronic links between their main trade partners. Individuals already apply to the Internet for electronic commerce. However a problem still remains: the gap due to the SMEs which are numerous along the logistic chain. In this paper, we will first explain the gap in the IT use by small transport firms, secondly we will present the use of information technologies in the transport logistics field. Then we will present the new way of indermediation in the transport and logistic, and we will finish by discussing how the role of these concerns would be modified by Internet/Intranet.
Passenger Choice Analysis for Seat Capacity Control: A Pilot Project in Scandinavian Airlines
Authors: Andersson S‐E.
Published: August 2006

A yield management research project in Scandinavian Airlines System (SAS) focuses upon passenger preferences in situations where the preferred flight, class alternative is sold out. The passenger then could deviate to a competitor; be recaptured onto another SAS flight; or pay the higher fare on a higher booking class (be a buyup). Class allocations possibly should reflect preferences for such options, particularly when prices are becoming operational control variables. Passenger preferences were estimated from choice analyses of interviews and logged bookings transactions. Needs of developing SAS present origin‐to‐destination heuristic were identified, and alternatives for revising the class allocation models were assessed. Issues to be resolved prior to an implementation were identified.
Using Expert System Rules to Establish Data for Intersections and Turns in Road Networks
Authors: Nielsen O.A. , Frederiksen R.D. , Simonsen N.
Published: August 2006

Delays and restrictions in intersections contribute significantly to the overall travel times in urban traffic networks and therefore also affect route choices. In practice, however, it is quite unusual to include intersection delays in traffic models, logistic models and route guidance systems. Time consuming and tedious data preparation together with the complexity of network updating is the main reason for this, as most transportation software applications can do the necessary calculations. In this paper, we report on the development of a procedure that can automate the task of adding data for intersection delay modelling to an existing network. The method requires a GIS‐based network with link attributes as input data. The method has developed as an extension tool applicable to existing networks and therefore supply of additional data is normally not required. By a set of ‘expert system rules’, the intersections are classified into a number of groups – such as prioritised and signalised intersections, wedges and Y‐junctions – and the required input data for turn delay models is established. The method has been tested on large‐scale networks with good results. Most of the required data was satisfactorily estimated, although some edits had to be made manually. This was mainly the case for roundabouts and for intersections with a very special geometry. In conclusion, the method greatly reduced the burden establishing data sets for intersection delay modelling in urban traffic networks.
An integrated optimal control and algorithm for commuting corridors
Authors: Wu J. , Chang G‐L.
Published: August 2006

An integrated optimal control model and its solution algorithm have been developed for commuting corridor management. Three traffic control measures, including ramp metering, intersection signal timing, and freeway flow diversion, have been incorporated and optimized simultaneously. As an improvement to our previous work, the presented model and algorithm have the following three unique features: (1) modeling traffic state evolution on surface streets with flow conservation within sections, flow transition between sections, and flow discharging at downstream intersections; (2) estimating time‐dependent model parameters adaptively with real‐time traffic measurements, rather than assuming as pre‐determined; and (3) having a limited‐step convergence property in its solution logic. Preliminary numerical tests have demonstrated the potential of the developed model and algorithm for integrated real‐time corridor control.
Variances of link travel time estimates: implications for optimal routes
Authors: Sen A. , Thakuriah P. , Zhu X‐Q. , Karr A.
Published: August 2006

In this paper, we explore the consequences of using link travel time estimates with high variance to compute the minimum travel time route between an origin and destination pair. Because of platoon formation or for other reasons, vehicles on a link separated by small headways tend to have similar travel times. In other words, the covariance of link travel times of distinct vehicles which are close together may not be zero. It follows that the variance of the mean of travel times obtained from a sample of n vehicles on a same link over small time intervals is of the form a+b/n where a and b would usually be positive. This result has an important implication for the quality of road network travel time information given by Intelligent Transportation Systems (ITS)—that the variance of the estimate of mean travel time does not go to zero with increasing n. Thus the quality of information disseminated by ITS is not necessarily improved by increasing the market penetration of vehicles monitoring the system with the necessary equipment (termed probe vehicles). Estimates of a and b for a set of links are presented in the paper and consequences for probe‐based ITS are explored by means of a simulation of such a system which is operational on an actual network.
LP‐based bounds for the container and multi‐container loading problem
Authors: Scheithauer G.
Published: August 2006

New relaxations are developed in this paper for problems of optimal packing of small (rectangular‐shaped) pieces within one or several larger containers. Based on these relaxations tighter bounds for the Container Loading Problem (CLP) and the Multi‐Container Loading Problem (MCLP) are obtained.

The new relaxations for the CLP and MCLP lead to linear programming problems. A corresponding solution approach is discussed which is based on a column generation technique. Results of computational tests are also given.
Minimizing army housing deficits with a DSS‐delivered heuristic programming model
Authors: Forgionne G.A.
Published: August 2006

The ineffcient use of existing onpost, or available offpost, assets can result in insuffcient or unnecessary Army housing construction requests. Insuffcient requests can leave Army personnel inadequately housed, compromise morale and jeopardize military preparedness, while unnecessary requests can waste scarce natural resources and, in the process, alienate local residents, environmentalists and other interest groups. This paper: (a) presents a decision‐support‐system‐delivered heuristic programming model that effciently utilizes scarce housing resources; and (b) demonstrates the significant economic and management benefits that can be achieved through the application of the model. The same concepts can be applied to the housing allocation problem faced by the other armed services, federal, state, local housing authorities and to related resource allocation problems in public and private enterprises.
An optimal schedule for dollar cost averaging under different transaction costs
Authors: Khouja M. , Lamb R.P.
Published: August 2006

Dollar cost averaging is a popular habit adopted by investors who recognize the diffculty in consistently timing the market. Recent technological innovations allow for the direct deposit of a predetermined portion of each paycheck into a brokerage account for the purchase of equities. Since most payperiods are biweekly or monthly, the automatic and frequent purchase of small amounts of equity produces substantial transaction costs. If funds were allowed to accumulate for a time in a money market account prior to equity purchase, then transaction costs may be lowered. However, since equity returns are generally more than that earned in the money market, delayed purchases would forfeit higher returns. In this study, we determine the optimal transaction size to maximize returns. We use the classical economic order quantity framework of inventory management and extend that framework to deal with the special discounting structures commonly offered by brokerage firms. Numerical examples and sensitivity analysis of fixed and variable transaction cost structure models are presented.
Algorithms for scheduling jobs on two serial duplicate stations
Authors: Savsar M. , Allahverdi A.
Published: August 2006

In automated assembly or production lines, some stations are duplicated due to their long cycle times. Material handling considerations may require these stations to be arranged in series rather than in parallel. Each job needs to be processed on any one of the duplicate stations. This study deals with scheduling of n available jobs on two serial duplicate stations in an automated production line. The performance measures considered are mean flowtime, makespan, and station idle time. After the problem is formulated, two algorithms are developed to determine the optimal schedules with respect to the performance measures.
Markovian analysis of production lines with Coxian‐2 service times
Authors: Vidalis M.I. , Papadopoulos H.T.
Published: August 2006

This paper is concerned with the analysis of reliable production lines. The service times at each station of the line are assumed to follow the Coxian‐2 distribution. Raw material arrives at the first station of the line which is assumed that is never empty. Buffers of non‐identical capacities are allowed between successive stations. The structure of the transition matrices of these specific type of production lines is examined and a recursive algorithm is developed for generating them, for any number of stations K. This method allows one to obtain the exact solution of a sparse linear system by the use of the Gauss–Seidel method. From the solution of these systems the throughput rate of the production lines is calculated. However, this algorithm is not computationally efficient as it is restricted by the size of the problem. The main contribution of this paper is the study of the transition matrices of production lines with Coxian service times.
The methodology of multiple‐criteria decision making in the optimization of an urban transportation system: case study of Poznań City in Poland
Authors: Żak J.
Published: August 2006

The methodology of multiple‐criteria decision making applied to the optimization of an urban transportation system is presented in the paper. Three mathematical models of different complexity are constructed to optimize the allocation of vehicles to certain routes in a mass transit system. All models take into account both passengers' and operator's objectives. The optimization problems are formulated in terms of multiple‐objective fuzzy linear programming and multiple‐objective non‐linear programming. The sensitivity and precision analysis of the models is carried out. Two interactive multi‐objective mathematical programming procedures are utilized to solve the problems. They generate samples of Pareto‐optimal compromise solutions and provide the decision maker (DM)with an effective tool that supports him/her in the decision making process. Finally, the DM selects the solution that best fits his or her expectations.
Production management practice in a developing country: a case study
Authors: Pizzolato N. D. , Sergio Gustavo Guerrero V.
Published: August 2006

A real application of the economic order quantity (EOQ)and the production scheduling problems, both of which are relevant to the production operation of a chemical firm with a single facility that produces to orders, are discussed. A number of difficulties, typical of a developing country environment, have precluded the direct use of traditional analytical instruments, and the options proposed as well as the origins of these difficulties are related. In the EOQ case, the approach chosen is a descriptive procedure that simulates the consequences of alternative policies. In the case of production scheduling, it is noted that setups are strongly sequence dependent and the satisfaction of due dates is a hard challenge. Therefore, the problem is seen as a sequencing with Earliness and Tardiness Penalties Problem, for which one heuristic method of simple conception is proposed. It is important to notice that organization and human development programs have played a predominant role in the efficiency gains, which is an outcome not unexpected in the less industrialized countries.
Fuzzy due‐date scheduling problem with fuzzy processing time
Authors: Itoh T. , Ishii H.
Published: August 2006

For most of scheduling problems, jobs' processing times and due‐dates are treated as certain values, but that is not proper to all actual situations. Processing times are not constant because of measurement errors in the data sets for deciding them and/or human actions in the manufacturing process. However, we may be permitted to exceed due‐dates slightly. In this paper, we propose a model dealing with uncertain processing times and flexible due‐dates in consideration of real situations. Assuming the times and due‐dates to be fuzzy numbers, and defining a fuzzy tardiness for a job's due‐date, we design to minimize the number of tardy jobs in our problem formulation.
Sensitivity formulas of performance in two‐server cyclic queueing networks with phase‐type distributed service times
Authors: Yin B. , Zhou Y. , Xi H. , Sun D.
Published: August 2006

With the approach of the infinitesimal generator perturbation, sensitivities of the steady‐state performance are studied in two‐server cyclic queueing networks with phase‐type distributed service times. Sensitivity formulas expressed by the potentials of the networks are given for parameter‐dependent performance functions. An algorithm to compute the potentials and the performance derivatives of the networks is given, and a numerical example is provided.
An investigation of genetic algorithms for the optimization of multi‐objective fisheries bioeconomic models
Authors: Mardle S.J. , Pascoe S. , Tamiz M.
Published: August 2006

The use of genetic algorithms (GA) for optimization problems offers an alternative approach to the traditional solution methods. GA follow the concept of solution evolution, by stochastically developing generations of solution populations using a given fitness statistic, for example the achievement function in goal programs. They are particularly applicable to problems which are large, non‐linear and possibly discrete in nature, features that traditionally add to the degree of complexity of solution. Owing to the probabilistic development of populations, GA do not distinguish solutions, e.g. local optima from other solutions, and therefore cannot guarantee optimality even though a global optimum may be reached. In this paper, a non‐linear goal program of the North Sea demersal fisheries is used to develop a genetic algorithm for optimization. Comparisons between the GA approach and traditional solution methods are made, in order to measure the relative effectiveness. General observations of the use of GA in multi‐objective fisheries bioeconomic models, and other similar models, are discussed.
Decision criteria with partial information
Authors: Puerto J. , Mármol A.M. , Monroy L. , Fernández F.R.
Published: August 2006

In this paper we use an extreme point approach to analyze some usual decision criteria for multiple attribute decision‐making problems when partial information about the importance of the attributes is available. The obtained results show that the decision criteria to be chosen depend not only on the rationality principles, but also on the structure of the information set. We apply the obtained criteria to problems where the set of actions to be evaluated are either in qualitative and/or quantitative scales.
Land management with GIS and multicriteria analysis
Authors: Joerin F. , Musy A.
Published: August 2006

In land management, conflicts are more frequent and stronger. Any important project on land becomes difficult to implement. MAGISTER (Multicriteria Analysis with GIS for TERritory) model proposes a decision support method to integrate multiple actors of land management. It is based on geographical information systems and multicriteria analysis. In land use problems, the study area is described by a set of homogeneous zones to reduce the numbers of alternatives. The homogeneity quality is assessed by use of a valued closeness relation developed in the domain of rough set theory. This function is based on the same principle as the valued outranking relation used in ELECTRE, which is then used to select the best zones, or classify them in predefined category. One application of the MAGISTER model concerns the realisation of a land suitability map for housing. Through eight criteria, this map integrates simultaneously the particularity of each place and the general principles of land management, which should be determined by decision‐makers.
IFORS: the formative years
Authors: Rand G.K.
Published: August 2006

In 1999 IFORS (The International Federation of Operational Research Societies) celebrated 40 years since its formation. The purpose of this article is to explain how it came into being following the first international conference in Operational Research, and to examine the foundations that were laid in the years leading up to its first General Meeting, held at the second international conference. A further article will examine several themes in IFORS' subsequent history.
Operations research and knowledge discovery: a data mining method applied to health care management
Authors: Delesie L. , Croes L.
Published: August 2006

The exponential growth of databanks creates opportunities to expand Operational Research. An example is the development of scientific approaches to “mine” intelligently the huge databanks that complex systems rely on for their management. The contribution presents an approach to exploit a health insurance databank to evaluate the performance of cardiovascular surgery nation wide.
A simulation model to evaluate the impact of environmental programmes on dairy farms
Authors: van Huylenbroeck G. , Jacobs G. , Vanrolleghem P.
Published: August 2006

A simulation model has been developed to determine the impact of the implementation of environmental programmes putting restrictions on fertiliser use and mowing date on dairy farms. In the paper, the simulation model is described and results showing the trade‐offs between the economic, environmental and nature protection criteria are given. Finally, the optimal compromise is found using multi‐criteria analysis.
A travelling salesman problem with allocation, time window and precedence constraints — an application to ship scheduling
Authors: Fagerholt K. , Christiansen M.
Published: August 2006

A Travelling Salesman Problem with Allocation, Time Window and Precedence Constraints (TSP‐ATWPC) is considered. The TSP‐ATWPC occurs as a subproblem of optimally sequencing a given set of port visits in a real bulk ship scheduling problem, which is a combined multi‐ship pickup and delivery problem with time windows and multi‐allocation problem. Each ship in the fleet is equipped with a flexible cargo hold that can be partitioned into several smaller holds in a given number of ways, thus allowing multiple products to be carried simultaneously by the same ship. The allocation constraints of the TSP‐ATWPC ensure that the partition of the ship's flexible cargo hold and the allocation of cargoes to the smaller holds are feasible throughout the visiting sequence. The TSP‐ATWPC is solved as a shortest path problem on a graph whose nodes are the states representing the set of nodes in the path, the last visited node and the accumulated cargo allocation. The arcs of the graph represent transitions from one state to another. The algorithm is a forward dynamic programming algorithm. A number of domination and elimination tests are introduced to reduce the state space. The computational results show that the proposed algorithm for the TSP‐ATWPC works, and optimal solutions are obtained to the real ship scheduling problem.
No‐wait and separate setup three‐machine flowshop with total completion time criterion
Authors: Allahverdi A. , Aldowaisan T.
Published: August 2006

This paper considers the three‐machine no‐wait flowshop problem with the objective of minimizing total completion time where setup times are considered as separate from processing times and sequence independent. We present optimal solutions for certain cases, and a dominance relation for the general case. We also develop and evaluate five heuristic algorithms for small and large number of jobs. Computational experience for up to 100 jobs shows that the proposed heuristics are quite effective and their performance do not depend on the number of jobs. The computational experience has been conducted for the uniform processing time distributions of U(1, 10) and U(1, 100). The best heuristic gives an overall average error of 0.47% for U(1, 10) and it gives an overall average error of 1.23% for U(1, 100).
Cointegration of stochastic multifractals with application to foreign exchange rates
Authors: Anh V.V. , Tieng Q.M. , Tse Y.K.
Published: August 2006

The existing concept of cointegration applies to integrated processes (in the Box‐Jenkins ARIMA framework) or processes with long‐range dependence. These processes are assumed to display a monoscaling behaviour (such as that of a fractional Brownian motion). On the other hand, many turbulent processes are known to be intermittent, hence possess multiscaling characteristics. This paper develops a concept of cointegration for these stochastic multifractals. A model is suggested for testing for cointegration and applied to the exchange rates of three major currencies.
Evolutionary algorithms for flowshop sequencing with non‐unique jobs
Authors: Burdett R.L. , Kozan E.
Published: August 2006

Sequencing problems are difficult combinatorial problems because of the extremely large search space of possible solutions and the large number of “local” optima that arise. Unlike other NP‐hard combinatorial problems, the search space, in general, for sequencing problems (under the makespan objective) consists of sequences with objective function values that lie within only a relatively small amount of each other. This means that when a change is made to the sequence, an improvement or non‐improvement is not easily recognised. This makes the problem much more difficult to solve. A number of constructive heuristics exist that obtain good solutions in a short period of time, however, the output of such algorithms is generally a single sequence which may not be feasible or preferred with respect to industry constraints. Other heuristic algorithms such as Simulated Annealing (SA) and Tabu Search (TS) have also been applied and successes have been reported. However, the performance is dependent upon a number of finely tuned parameters and the output is again only a single solution. For these reasons, Evolutionary Algorithms (EAs) may be suitable solution strategy, for which limited research has been performed. In this research, a number of new EAs have been proposed and a number of modifications have been made to several constructive algorithms to cope with non‐unique jobs or jobs with multiple demands. A numerical comparison of a number of benchmark problems and real data of a truck assembly line has also been presented.
Quantitative decision making for cued land reconnaissance: a defence case study
Authors: Yue Y. , Scutter M.
Published: August 2006

Helping commanders make more informed decisions is one of the most important roles played by defence operations analysts. This paper presents a defence case study of quantitative decision making. It develops a decision model for cued land reconnaissance missions that treats detecting, identifying, and destroying a hostile target to protect an asset as an integral process. The paper investigates issues such as whether an information assessment system, which provides improved knowledge about the nature of the cue, is necessary and what kind of reconnaissance platforms should be used under various conditions. Using a decision tree and evaluating all possible outcomes, the model derives the best course of action based on expected values. Then serials of sensitivity analysis are carried out to account for uncertainties of the scenarios, and their implications are explored. This illustrates that decision tree methodology can be used to analyse complex sequential decision problems in real military situations, and uncertainties can be taken into account in the decision making process.
A modeling framework for hospital location and service allocation
Authors: Chu S.C.K. , Chu L.
Published: August 2006

This paper proposes a modeling framework to plan for the supply and demand matching of public hospital beds in Hong Kong for the future years till 2006. It addresses the planning issues of (1) hospital locations and (2) service allocations, which include new services distribution as well as existing services redistribution. The structure of such a general modeling framework is emphasized here, with small‐scaled numerical examples as illustrations for its intended useful purposes.
How to keep good schemata using cross‐over operators for permutation problems
Authors: Djerid L. , Portmann M‐C.
Published: August 2006

The schemata theory proposed by Holland in 1975 for the genetic algorithm approach is based on a binary representation of the problem solutions. When the description of the solution needs some more complex representation (called generally symbolic representation) and when the one‐point classical cross‐over operator must be replaced by some more complicated operator, then the environment of the schemata theory disappears and other conditions must be taken into account in order to ensure the efficiency of the genetic algorithms. In a previous paper, we have already proposed some performance indicators, which try to extend the basic schemata theory for permutation problems, and we have tested the quality of a list of cross‐over operators using these indicators. In the present paper, we show how an analytical approach may be developed in order to avoid the experimental approach for some permutation cross‐over operators and some indicators.
Variety is the spice of life: combining soft and hard OR/MS methods
Authors: Mingers J.
Published: August 2006

Some observers have expressed concern over the state of the OR/MS profession, especially as to its failure to tackle complex, messy problems. One response has been to develop various “soft” methods (also called “problem structuring methods”) that focus on the human and political aspects of OR/MS interventions. Recent work, both theoretical and practitioner‐based, involves the combination of several methods in a particular project (multimethod). Often the combination includes both hard (quantitative) and soft (qualitative) approaches. This paper illustrates the utility of soft methods, and in particular their combination, with recently published case studies. It then proposes an approach to the process of combining methods, including several frameworks and techniques to assist in selecting and linking different methods. Finally, it discusses future research in this field.
Patterning the geographies of organ transplantation: corporeality, generosity and justice
Authors: Davies Gail
Published: August 2006

Organ transplantation is now an established treatment for patients with end‐stage organ failure, yet there are spatial inequalities in access to this procedure. This paper explores the uneven geographies of kidney transplantation in London, arguing that inequalities in access to organ transplantation are created through interlocking spatialities of corporeal difference, enacted through global movements of populations, national organ transplantation protocols and the internal immunological spaces of the body. The combination of these processes, operating at different scales, has produced a distinctive configuration in the embodiment of risk in relation to kidney transplants, particularly born by London's Black and Asian communities. Two ethical dimensions to this geography of organ transplantation are explored here: the ethical responsiveness to others shaping the generous practices of organ donation, and the medical practices categorizing difference through techniques of blood typing, tissue matching and the spatial organization of organ transplantation. In concluding, I argue both are critical to understanding the links between ethics and justice in the geographies of organ exchange in London. Further, I suggest geography is central to political debate about the exchange of biological material elsewhere, for it is only through tracing the intersection of ethical, corporeal and technological practices in situ that we can fully reflect on questions of justice within the developing bioeconomy.
A working land: crofting communities, place and the politics of the possible in post‐Land Reform Scotland1
Authors: Fiona A , Mackenzie D
Published: August 2006

In the context of the Land Reform (Scotland) Act 2003, this paper examines the political possibilities that are created when land is removed as a commodity from circuits of global capital and when, in areas under crofting tenure, it comes under collective ownership. Drawing evidence from the case of the North Harris Trust, Isle of Harris, the largest community purchase of land thus far, the paper considers how place is re‐configured in complex and contingent ways through the re‐working of the materiality and meanings of the land and of nature. The latter includes disturbing class‐based and colonizing discourses of ‘wilderness’, on the one hand and, on the other, exploring the ways through which the wind is commodified. The paper argues that this re‐constitution of land and nature does not lead in a simplistic way to a reversal of processes of enclosure (and globalization) but rather, through the co‐performance of land and nature in the new political spaces created by a community trust, the relationship between the ‘local’ and the ‘global’ is altered such that a more sustainable and socially just future may be imagined.
Presence–Absence versus Abundance Data for Monitoring Threatened Species
Authors: JOSEPH LIANA N. , FIELD SCOTT A. , WILCOX CHRIS , POSSINGHAM HUGH P.
Published: August 2006

Abstract:  Effective detection of population trend is crucial for managing threatened species. Little theory exists, however, to assist managers in choosing the most cost‐effective monitoring techniques for diagnosing trend. We present a framework for determining the optimal monitoring strategy by simulating a manager collecting data on a declining species, the Chestnut‐rumped Hylacola (Hylacola pyrrhopygia parkeri), to determine whether the species should be listed under the IUCN (World Conservation Union) Red List. We compared the efficiencies of two strategies for detecting trend, abundance, and presence–absence surveys, under financial constraints. One might expect the abundance surveys to be superior under all circumstances because more information is collected at each site. Nevertheless, the presence–absence data can be collected at more sites because the surveyor is not obliged to spend a fixed amount of time at each site. The optimal strategy for monitoring was very dependent on the budget available. Under some circumstances, presence–absence surveys outperformed abundance surveys for diagnosing the IUCN Red List categories cost‐effectively. Abundance surveys were best if the species was expected to be recorded more than 16 times/year; otherwise, presence–absence surveys were best. The relationship between the strategies we investigated is likely to be relevant for many comparisons of presence–absence or abundance data. Managers of any cryptic or low‐density species who hope to maximize their success of estimating trend should find an application for our results.
Do Physicians and Their Relatives Have a Decreased Rate of Cesarean Section? A 4‐Year Population‐Based Study in Taiwan
Authors: Chou Yiing‐Jenq , Huang Nicole , Lin I‐Feng , Deng Chung‐Yeh , Tsai Yi‐Wen , Chen Long‐Shen , Lee Cheng‐Hua
Published: August 2006

ABSTRACT:  Background:
The increased rate of cesarean deliveries may be partly due to a lack of consumer knowledge. Assuming that physicians and their relatives are well informed of the risks and benefits associated with the different methods of delivery, our goal was to compare cesarean rates between female physicians, female relatives of physicians, and women with high socioeconomic status in Taiwan.
Methods:
Two subgroups of 588 female physicians and 5,021 relatives of physicians aged 20 to 50 years were compared with 93,737 pregnant women with a monthly wage $40,000 New Taiwan (NT) dollars or more as identified in nationwide National Health Insurance databases of Taiwan from 2000 to 2003.
Results:
Female physicians (adjusted odds ratio 0.66; 95% CI 0.47, 0.93) and female relatives of physicians (adjusted odds ratio 0.84; 95% CI 0.74, 0.95) were significantly less likely to undergo a cesarean section than other high socioeconomic status women, adjusted for clinical and nonclinical factors.
Conclusions:
In this study, the cesarean delivery rate was lower among women who may have greater access to medical knowledge. However, the lower rates observed among female physicians and physician relatives in Taiwan are still considerably higher than the national averages of many countries. This finding suggests that other than information, practice patterns, and social and cultural milieu may play a role. (BIRTH 33:3 September 2006)
Why Do Women Go Along with This Stuff?
Authors: Klein Michael C. , Sakala Carol , Simkin Penny , Davis‐Floyd Robbie , Rooks Judith P. , Pincus Jane
Published: August 2006

PREFACE:  Normal childbirth has become jeopardized by inexorably rising interventions around the world. In many countries and settings, cesarean surgery, labor induction, and epidural analgesia continue to increase beyond all precedent, and without convincing evidence that these actions result in improved outcomes (1,2). Use of electronic fetal monitoring is endemic, despite evidence of its ineffectiveness and consequences for most parturients (1,3); ultrasound examinations are too often done unnecessarily, redundantly, or for frivolous rather than indicated reasons (4); episiotomies are still routine in many settings despite clear evidence that this surgery results in more harm than good (5); and medical procedures, unphysiological positions, pubic shaving and enemas, intravenous lines, enforced fasting, drugs, and early mother‐infant separation are used unnecessarily (1). Clinicians write and talk about the ideal of evidence‐based obstetrics, but do not practice it consistently, if at all.

Why do women go along with this stuff? In this Roundtable Discussion, Part 2, we asked some maternity care professionals and advocates to discuss this question. (BIRTH 33:3 September 2006)
Metabotropic Glutamate Receptor Subtype 5 Antagonists MPEP and MTEP
Authors: Lea Paul M. , Faden Alan I.
Published: August 2006

Glutamate regulates the function of central nervous system (CNS), in part, through the cAMP and/or IP3/DAG second messenger‐associated metabotropic glutamate receptors (mGluRs). The mGluR5 antagonist 2‐methyl‐6‐(phenylethynyl)‐pyridine (MPEP) has been extensively used to elucidate potential physiological and pathophysiological functions of mGluR5. Unfortunately, recent evidence indicates significant non‐specific actions of MPEP, including inhibition of NMDA receptors. In contrast, in vivo and in vitro characterization of the newer mGluR5 antagonist 3‐[(2‐methyl‐1,3‐thiazol‐4‐yl)ethynyl]pyridine (MTEP) indicates that it is more highly selective for mGluR5 over mGluR1, has no effect on other mGluR subtypes, and has fewer off‐target effects than MPEP. This article reviews literature on both of these mGluR5 antagonists, which suggests their possible utility in neurodegeneration, addiction, anxiety and pain management.
Prostanoids in the Therapy of Glaucoma
Authors: Ishida Naruhiro , Odani‐Kawabata Noriko , Shimazaki Atsushi , Hara Hideaki
Published: August 2006

Elevated intraocular pressure (IOP) is one of the most important risk factors for the development of glaucoma, which is a progressive optic neuropathy. Lowering IOP is currently the only therapeutic approach to the therapy of glaucoma. Since the use of pilocarpine eye drops for glaucoma treatment was reported in the late 1870s, academic researchers and pharmaceutical companies attempted to discover new drugs with more potent, prolonged, and safer IOP‐reducing effects. These persistent efforts finally paid off, and prostanoids with FP‐receptor agonist activity were found to be very potent IOP‐lowering agents. To date, three prostanoids (latanoprost, travoprost and bimatoprost) have been launched in many countries, and now a new FP‐receptor agonist, tafluprost, is entering clinical development. All of these prostanoids are superior to the β‐adrenoceptor antagonists in their IOP‐lowering efficacy, and no severe side effects have been reported in their long‐term clinical use. In addition, tafluprost may be expected to improve ocular blood flow. Hence, prostanoids currently occupy center stage among glaucoma medications. It cannot be denied that in terms of efficacy, safety, patient compliance, and medical economy prostanoids are currently the first‐line medicines among ocular antihypertensive drugs.
Triflusal: An Antiplatelet Drug with a Neuroprotective Effect?
Authors: González‐Correa José Antonio , De La Cruz José Pedro
Published: August 2006

Triflusal is a derivative of salicylic acid with a well‐established platelet aggregation inhibitory profile. Its pharmacokinetic and pharmacodynamic properties differ, however, somewhat from those of acetylsalicylic acid. A number of recent experimental and clinical studies have shown that triflusal is a potentially useful choice in the treatment and prophylaxis of brain ischemia because of its antithrombogenic as well as neuroprotective effects. Its antithrombogenic effect has been demonstrated at the clinical as well as at the experimental level, while its neuroprotective effect has been shown only in experimental models. The drug interferes with thrombogenesis by inhibiting thromboxane synthesis and increasing the levels of cAMP and nitric oxide. Its neuroprotective action is the result of its antioxidant and antiinflammatory effects in brain tissue. From a clinical standpoint triflusal is similar in efficacy to acetylsalicylic acid in preventing stroke, but has less adverse effects, especially it is less likely to cause bleeding. Because of its pharmacodynamic properties and lower rate of adverse reactions, triflusal may be a useful alternative to acetylsalicylic acid in the prevention of stroke.
Pharmacological Profile of U‐37883A, a Channel Blocker of Smooth Muscle‐Type ATP‐Sensitive K+ Channels
Authors: Teramoto Noriyoshi
Published: August 2006

U‐37883A (PNU‐37883A, guanidine; 4‐morpholinecarboximidine‐N‐1‐adamantyl‐N′‐cyclohexyl hydrochloride) was originally developed as a potential diuretic with specific binding in kidney and vascular smooth muscle rather than in brain or pancreatic β cells. U‐37883A inhibits ATP‐sensitive K+ channels (KATP channels) in vascular smooth muscle at submicromolar concentrations whilst even at high concentrations (≥10 μM) it has no inhibitory effect at pancreatic, cardiac or skeletal KATP channels. Thus, it is generally thought that U‐37883A is a selective inhibitor of vascular smooth muscle KATP channels.

Approximately one decade ago, KATP channels were cloned and found to consist of at least two subunits: an inwardly‐rectifying K+ channel six family (Kir6.x; Kir6.1 and Kir6.2) which forms the ion conducting pore and a modulatory sulphonylurea receptor (SUR.x; SUR1, SUR2A, and SUR2B) that accounts for several pharmacological properties. It is generally believed that different combinations of Kir6.x and SUR.x determine the molecular properties of KATP channels. Thus, Kir6.2/SUR1 channel represents the pancreatic β‐cell KATP channel, Kir6.2/SUR2A channel is thought to represent the cardiac KATP channel, whereas Kir6.1/SUR2B channel is likely to represent the vascular smooth muscle KATP channel.

Recent molecular studies have shown that U‐37883A selectively suppresses the activity of recombinant KATP channels which contain Kir6.1 subunits in the channel pore unit. It was thus thought that U‐37883A was a selective pharmacological tool which could be used to investigate the activity of vascular smooth muscle KATP channels. However, due to its multiple pharmacological actions on several ion channels and poor tissue selectivity, U‐37883A should not be viewed as a selective blocker of smooth muscle KATP channels.
Ambrisentan, a Non‐peptide Endothelin Receptor Antagonist
Authors: Vatter Hartmut , Seifert Volker
Published: August 2006

Increasing numbers of experimental investigations and recently also of clinical trials strongly suggest an integral involvement of the endothelin (ET)‐system in the pathophysiology of a variety of disease states, mainly of the cardiovascular system. Ambrisentan (LU 208075), a selective ETA‐receptor antagonist, is an orally active diphenyl propionic acid derivative. It has been shown to have a very promising efficacy to safety ratio in the initial clinical trials. Phase II and Phase III trials with ambrisentan in pulmonary arterial hypertension have been performed. The pharmacological properties and data from the experimental investigations suggest additional possible uses of ambrisentan in the prevention of reperfusion injury after organ transplantation and in restenosis following coronary artery dilatation. Furthermore, the pharmacological profile of ambrisentan indicates that this drug may also be suitable in the treatment of cerebrovascular disorders. In the present article basic investigations, animal studies and clinical trials with ambrisentan are reviewed. This review may help to define pathophysiological conditions, in which ambrisentan could be indicated and further evaluated in appropriate preclinical and clinical trials.
Rho‐kinase inhibition enhances axonal regeneration after peripheral nerve injury
Authors: Hiraga Akiyuki , Kuwabara Satoshi , Doya Hideo , Kanai Kazuaki , Fujitani Masashi , Taniguchi Junko , Arai Kimihito , Mori Masahiro , Hattori Takamichi , Yamashita Toshihide
Published: August 2006

Abstract  In injured adult neurons, the process of axonal regrowth and reestablishment of the neuronal function have to be activated. We assessed in this study whether RhoA, a key regulator of neurite elongation, is activated after injury to the peripheral nervous system. RhoA is activated in motoneurons but not in Schwann cells after mouse sciatic nerve injury. To examine whether the activation of RhoA and its effector, Rho‐kinase, retards axon regeneration of injured motoneurons, we employed a Rho‐kinase inhibitor, fasudil. Amplitudes of distally evoked compound muscle action potentials are increased significantly faster after axonal injury in mice treated with fasudil compared with controls. Histological analysis shows that fasudil treatment increases the number of regenerating axons with large diameter, suggesting that axon maturation is facilitated by Rho‐kinase inhibition. In addition, fasudil does not suppress the myelination of regenerating axons. These findings suggest that RhoA/Rho‐kinase may be a practical molecular target to enhance axonal regeneration in human peripheral neuropathies.
Semiparametric Analysis of Two‐Level Bivariate Binary Data
Authors: Naskar Malay , Das Kalyan
Published: August 2006

SummaryIn medical studies, paired binary responses are often observed for each study subject over timepoints or clusters. A primary interest is to investigate how the bivariate association and marginal univariate risks are affected by repeated measurements on each subject. To achieve this we propose a very general class of semiparametric bivariate binary models. The subject‐specific effects involved in the bivariate log odds ratio and the univariate logit components are assumed to follow a nonparametric Dirichlet process (DP). We propose a hybrid method to draw model‐based inferences. In the framework of the proposed hybrid method, estimation of parameters is done by implementing the Monte Carlo expectation‐maximization algorithm. The proposed methodology is illustrated through a study on the effectiveness of tibolone for reducing menopausal problems experienced by Indian women. A simulation study is also conducted to evaluate the efficiency of the new methodology.
A Class of Multiplicity Adjusted Tests for Spatial Clustering Based on Case–Control Point Data
Authors: Tango Toshiro
Published: August 2006

SummaryA class of tests with quadratic forms for detecting spatial clustering of health events based on case–control point data is proposed. It includesCuzick and Edwards'stest statistic (1990,Journal of theRoyal Statistical Society, Series B52,73–104). Although they used the property of asymptotic normality of the test statistic, we show that such an approximation is generally poor for moderately large sample sizes. Instead, we suggest a central chi‐square distribution as a better approximation to the asymptotic distribution of the test statistic. Furthermore, not only to estimate the optimal value of the unknown parameter on the scale of cluster but also to adjust for multiple testing due to repeating the procedure by changing the parameter value, we propose theminimum of the profile p‐value of the test statistic for the parameteras an integrated test statistic. We also provide a statistic to estimate the areas or cases which make large contributions to significant clustering. The proposed methods are illustrated with a data set concerning the locations of cases of childhood leukemia and lymphoma and another on early medieval grave site locations consisting of affected and nonaffected grave sites.
Joint Modeling of Progression of HIV Resistance Mutations Measured with Uncertainty and Failure Time Data
Authors: Hu Chengcheng , De Gruttola Victor
Published: August 2006

SummaryDevelopment of HIV resistance mutations is a major cause for failure of antiretroviral treatment. This article proposes a method for jointly modeling the processes of viral genetic changes and treatment failure. Because the viral genome is measured with uncertainty, a hidden Markov model is used to fit the viral genetic process. The uncertain viral genotype is included as a time‐dependent covariate in a Cox model for failure time, and an expectation‐maximization algorithm is used to estimate the model parameters. This model allows simultaneous evaluation of the sequencing uncertainty and the effect of resistance mutation on the risk of virological and immunological failures. Various model checking tests are provided to assess the appropriateness of the model. Simulation studies are performed to investigate the finite‐sample properties of the proposed methods, which are then applied to data collected in three phase II clinical trials testing antiretroviral treatments containing the drug efavirenz.