Optimal maintenance and replacement of extraction machinery

This paper considers a problem of optimal preventive maintenance and replacement schedule of equipment devoted to extracting resources from known deposits. Typical examples are oil drills, mine shovels, etc. At most one replacement of the existing machinery by a new one is allowed. The problem is formulated as an optimal control problem subject to the state constraint that the remaining deposit at any given time is nonnegative. We show that the optimal preventive maintenance, production rates, and the replacement and salvage times of the existing machinery and the new one, if required, can be obtained by solving sequentially a series of free-end-point optimal control problems. Moreover, an algorithm based on this result is developed and used to solve two illustrative examples.     

Interval Time Series Analysis with an Application to the Sterling-Dollar Exchange Rate

Traditional econometrics has long employed ＂points＂ to measure time series data. In real life situations, however, it suffers the loss of volatility information, since many variables are bounded by intervals in a given period. To address this issue, this paper provides a new methodology for interval time series analysis. The concept of ＂interval stochastic process＂ is formally defined as a counterpart of ＂stochastic process＂ in point-based econometrics. The authors introduce the concepts of interval stationarity, interval statistics （including interval mean, interval variance, etc.） and propose an interval linear model to investigate the dynamic relationships between interval processes. A new interval-based optimization approach for estimation is proposed, and corresponding evaluation criteria are derived. To demonstrate that the new interval method provides valid results, an empirical example on the sterling-dollar exchange rate is presented.     

Power-Based Arbitrary Decisional Actions in the Resolution of MIS Project Issues: A Project Manager's Action Research Perspective

As a management information systems (MIS) project manager and an action researcher, the author examined, over time, the influence on information system development (ISD) of the informal sociopolitical organizational actions. The paper reports two cases of action research findings concerning the effect on ISD project implementation processes of power-based arbitrary decisional actions in bureaucratic environments. The research focused on the relationship of such unilateral actions to the interconnected subprocesses of deliberate and conscious attempts by the ISD project members to define and resolve system implementation issues. A suggested conceptual framework for the issue-resolution processes (IRP's) and obstacle-coping processes (OCP's) is based on the author's IRP/OCP-related behavioral constructs and theoretical models dealing with soft-systems issues, especially appreciative system theory and soft-systems methodology, and innovative flexible, "complementarist" (Sinn, 1998) or pluralist problem-solving approaches.     

A multiple intelligent agent system for credit risk prediction via an optimization of localized generalization error with diversity

Company bankruptcies cost billions of dollars in losses to banks each year. Thus credit risk prediction is a critical part of a bank＇s loan approval decision process. Traditional financial models for credit risk prediction are no longer adequate for describing today＇s complex relationship between the financial health and potential bankruptcy of a company. In this work, a multiple classifier system （embedded in a multiple intelligent agent system） is proposed to predict the financial health of a company. In our model, each individual agent （classifier） makes a prediction on the likelihood of credit risk based on only partial information of the company. Each of the agents is an expert, but has limited knowledge （represented by features） about the company. The decisions of all agents are combined together to form a final credit risk prediction. Experiments show that our model out-performs other existing methods using the benchmarking Compustat American Corporations dataset.     

ROLE OF α-PSEUDO-UNIVEX FUNCTIONS IN VECTOR VARIATIONAL-LIKE INEQUALITY PROBLEMS

In this paper, we introduce a new class of generalized convex function, namely, a-pseudounivex function, by combining the concepts of pseudo-univex and α-invex functions. Further, we establish some relationships between vector variational-like inequality problems and vector optimization problems under the assumptions of α-pseudo-univex functions. Results obtained in this paper present a refinement and improvement of previously known results.     

A relevant in vitro rat model for the evaluation of blood-brain barrier translocation of nanoparticles

Poly(MePEG₂₀₀₀cyanoacrylate-co-hexadecylcyanoacrylate) (PEG-PHDCA) nanoparticles have demonstrated their capacity to reach the rat central nervous system after intravenous injection. For insight into the transport of colloidal systems across the blood-brain barrier (BBB), we developed a relevant in vitro rat BBB model consisting of a coculture of rat brain endothelial cells (RBECs) and rat astrocytes. The RBECs used in our model displayed and retained structural characteristics of brain endothelial cells, such as expression of P-glycoprotein, occludin and ZO-1, and immunofluorescence studies showed the specific localization of occludin and ZO1. The high values of transendothelial electrical resistance and low permeability coefficients of marker molecules demonstrated the functionality of this model. The comparative passage of polyhexadecylcyanoacrylate and PEG-PHDCA nanoparticles through this model was investigated, showing a higher passage of PEGylated nanoparticles, presumably by endocytosis. This result was confirmed by confocal microscopy. Thanks to a good in vitro/in vivo correlation, this rat BBB model will help in understanding the mechanisms of nanoparticle translocation and in designing new types of colloidal carriers as brain delivery systems.Received 4 March 2005; accepted 14 April 2005     

Protein kinase C and phospholipase D: intimate interactions in intracellular signaling

Diacylglycerol (DAG) was discovered as a potent lipid second messenger with protein kinase C (PKC) as its major cellular target more than 25 years ago. There is increasing evidence of significant complexity within lipid signaling, and the classical DAG-PKC model no longer stands alone but is part of a larger bioactive lipid universe involving glycerolipids and sphingolipids. Multiple layers of regulation exist among PKC- and DAG-metabolizing enzymes such as phosphatidylcholine (PC)-specific phospholipase D, and cross-talk exists between the glycerolipid and sphingolipid pathways, with PKC at the center. Currently, there is intense interest in the question of whether DAG derived from PC can function as a lipid second messenger and regulate PKC analogous to DAG derived from phosphatidylinositol-4,5-bisphosphate (PIP₂). To address these issues and incorporate DAG-PKC and other signaling pathways into an expanded view of cell biology, it will be necessary to go beyond the classical approaches and concepts.Received 29 November 2004; received after revision 18 January 2005; accepted 4 March 2005This work is dedicated to the memory of Dr. Yasutomi Nishizuka, the discoverer of protein kinase C, who was both a gentleman and a scientist.     

Nucleotide analogues as probes for DNA polymerases

Transmission of the genetic information from the parental DNA strand to the offspring is crucial for the survival of any living species. In nature, all DNA synthesis in DNA replication, recombination and repair is catalyzed by DNA polymerases and depends on their ability to select the canonical nucleobase pair from a pool of structurally similar building blocks. Recently, a wealth of valuable new insights into DNA polymerase mechanisms have been gained through application of carefully designed synthetic nucleotides and oligonucleotides in functional enzyme studies. The applied analogues exhibit features that differ in certain aspects from their natural counterparts and, thus, allow investigation of the involvement and efficacy of a chosen particular aspect on the entire complex enzyme mechanism. This review will focus on a depiction of the efforts that have been undertaken towards the development of nucleotide analogues with carefully altered properties. The different approaches will be discussed in the context of the motivation and the problem under investigation.Received 16 March 2005; received after revision 5 May 2005; accepted 8 June 2005