bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative liver functions in Turner syndrome with and without hormone replacement therapy
Authors: Gravholt Claus Højbjerg , Poulsen Henrik Enghusen , Ott Peter , Christiansen Jens Sandahl , Vilstrup Hendrik 
Published: May 2007

Background: Studies have documented elevated levels of liver enzymes in many females with Turner syndrome (TS). Histology has shown a range of changes. Treatment with female hormone replacement therapy (HRT) reduces liver enzymes.
Aim: To study quantitative liver functions in TS in detail with and without HRT.
Design: Randomized crossover study with active treatment (HRT in TS and P-pill in controls) or no treatment.
Subjects: Women with TS (n = 8, age 29.7 ± 5.6 (mean ± s.d.) years), verified by karyotype, and age-matched controls (C; n = 8, age 27.3 ± 4.9 years).
Methods: We determined liver enzymes in blood, used the galactose elimination capacity to assess hepatocyte cytosol activity, plasma clearance of indocyanine green to assess excretory function, antipyrine clearance to estimate microsomal activity, and the functional hepatic nitrogen clearance (FHNC) to assess mitochondrial-cytosolic metabolic capacity for conversion of amino-nitrogen.
Results: Liver enzymes were elevated in untreated TS and reduced by HRT. The hepatic capacities for conversion of galactose, indocyanine green, and antipyrine were normal and did not change by HRT. The FHNC was marginally reduced (untreated TS vs C: 19.4 ± 5.4 vs 25.2 ± 7.3 L/h, P = 0.1). FHNC changed slightly with HRT in TS (19.4 ± 5.4 vs 24.4 ± 10.2 L/h, P = 0.2).
Conclusions: The elevations of liver enzymes in untreated TS are readily suppressed by HRT. Quantitative liver functions in TS are comparable to controls and are not affected by HRT.
Modifizierung der Holzeigenschaften durch Enzyme | Modification of wood properties through enzymes
Authors: Wagenführ André , Tech Sören , Unbehaun Holger 
Published: May 2007

The addition of phenol oxidising enzyme preparations leads to a change in the fibre structure of lignocellulose products. This means that positive material properties can be selectively put in. In the production of materials the use of activated ownfibre binding forces only makes sense when the production process ensures that fibres are as close to one another as possible. This can be accomplished by fine tuning the density of the material to the method in question. Material densities of over 600 kg/m3 are necessary for dry method approaches. With wet methods, on the other hand, the properties of material can be improved starting from a density of 160 kg/m3. A good distribution and the use of additionally created hydro-bridge builders are responsible for this. The employment of charge carriers during the processing with a wet method also has a positive influence on the physical properties. The suspended particles that become detached from the fibre in the process bind together and are concentrated on the surface of the fibre.
To improve the steering of the process with the wet method further enzymatic treatment steps in lignocellulose can be carried out with micro- and nano-particle systems. This can be done via combinations of cationic starch or cationic polyacrylamide. With these systems the cationic polymer is added to the fibre suspension first, followed by the micro-particle components. Both the levels of additives used and the required incubation times can thereby be markedly reduced. Here for the first time we succeeded in using enzymes in processing technically relevant dimensions and were therefore able to renounce the addition of synthetic binding means without impairing the properties of the material.
Das Theorem der übereinstimmenden Zustände und die Quantentheorie der Gase und Flüssigkeiten
Authors: Byk A. 
Published: May 2007

AbstractDas Theorem der übereinstimmenden Zustände und die Sonderstellung der Substanzen mit niedriger kritischer Temperatur. — Quantentheoretische Verallgemeinerung des Theorems der übereinstimmenden Zustände („Quantentheorem der übereinstimmenden Zustände”︁). — Prüfung des Quantentheorems an den Zustandsgleichungen der Sättigung: 1. Berechnung von Dampfdruckgleichungen und von Siedepunkten; 2. Berechnung von Dampfvolumgleichungen und von Siedevolumina; 3. Berechnung des kritischen Koeffizienten. — Die Thermodynamik der Gase und Flüssigkeiten und die Quantentheorie. Absolute Größen und Relativitätsprinzip. — Zusammenfassung.
Time‐series analysis of traffic updates in loss systems
Authors: Filipiak Janusz , Chemouil Prosper 
Published: May 2007

AbstractThe paper deals with time‐series analysis of one‐line traffic measurements in loss systems. Discrete‐time stochastic models are derived for finite‐capacity trunk groups with non‐exponential distributions of interarrival and service times. The modelling accuracy is characterized by a prediction error. Simulation results are used to assert situations when the application of the proposed modelling technique is practical. Finally the adaptive Kalman filter is used to deal with cases when the statistics of observed processes are not known a priori.
Asymptotic behaviour of ornstein‐uhlenbeck first‐passage‐time density through periodic boundaries
Authors: Sacerdote L. 
Published: May 2007

AbstractUse of the integral equation proposed by Buonocore et al.1 is made to obtain the asymptotic form of the first‐passage‐time p.d.f. for a normalized Ornstein‐Uhlenbeck process through a periodic boundary.
Compartmental models with phase‐type residence‐time distributions
Authors: Faddy M. J. 
Published: May 2007

AbstractPhase‐type (PH) probability distributions provide a versatile class of distributions, and are shown to fit naturally into a Markovian compartmental system, where “individuals” or “particles” move between a series of compartments, so that phase‐type compartmental residence‐time distributions can be incorporated simply by increasing the size of the system. Examples of PH distributions covering a variety of behaviours are given, and an application involving data analysis is included.
Recursive partition and amalgamation with the exponential family: Theory and applications
Authors: Ciampi A. , Lou Z. , Lin Qian , Negassa A. 
Published: May 2007

AbstractThe theory of tree‐growing (RECPAM approach) is developed for outcome variables which are distributed as the canonical exponential family. The general RECPAM approach (consisting of three steps: recursive partition, pruning and amalgamation), is reviewed. This is seen as constructing a partition with maximal information content about a parameter to be predicted, followed by simplification by the elimination of ‘negligible’ information. The measure of information is defined for an exponential family outcome as a deviance difference, and appropriate modifications of pruning and amalgamation rules are discussed. It is further shown how the proposed approach makes it possible to develop tree‐growing for situations usually treated by generalized linear models (GLIM). In particular, Poisson and logistic regression can be tree‐structured. Moreover, censored survival data can be treated, as in GLIM, by observing a formal equivalence of the likelihood under random censoring and an appropriate Poisson model. Three examples are given of application to Poisson, binary and censored survival data.
Expert systems as a tool for statistics: A review
Authors: Hatabian Gérard , Augendre Hervé 
Published: May 2007

AbstractThe current state of using expert system (ES) techniques for statistics is expounded through the difficulties of defining the notion of statistical expert system (SES) and through several well‐known examples. The main characteristics of statistical expertise, and particularly the important concept of strategy are emphasized. The current state of SESs is seen in the context of the global trend of the evolution of ES, i.e. within the growth of second generation expert system (SGESs). The knowledge base of these ESs represent an attempt to represent not only experts' knowledge but also the way experts acquire their expertise, thanks to the existence of an underlying model. We show through many examples how far SESs are and/or will be able to be SGESs.
An imputation method for dealing with missing data in regression
Authors: Cooper Lee G. , De Leeuw Jan , Sogomonian Aram G. 
Published: May 2007

AbstractWe develop two methods for imputing missing values in regression situations. We examine the standard fixed‐effects linear‐regression modelY = Xβ + ϵ, where the regressorsXare fixed and ϵ is the error term. This research focuses on the problem of missingXvalues. A particular component of market‐share analysis has motivated this research where the price and other promotional instruments of each brand are allowed to have their own impact on the total sales volume in a consumer‐products category. When a brand is not distributed in a particular week, only a few of the many measures occurring in that observation are missing. ‘What values should be imputed for the missing measures?’ is the central question this paper addresses. This context creates a unique problem in the missing‐data literature, i.e. there is no true value for the missing measure. Using influence functions, from robust statistics we develop twoloss functions, each of which is a function of the missing and existingXvalues. These loss functions turn out to be sums of ratios of low‐order polynomials. The minimization of either loss function is an unconstrained non‐linear‐optimization problem. The solution to this non‐linear optimization leads to imputed values that have minimal influence on the estimates of the parameters of the regression model. Estimates using the method for replacing missing values are compared with estimates obtained via some conventional methods.
A non‐parametric competing risks model for manpower planning
Authors: McClean Sally , Gribbin Owen 
Published: May 2007

AbstractOne of the most important variables for manpower planners is duration until a specified event occurs. This is frequently the completed length of service until leaving a job, but may also include such variables as length of service in a grade until promotion, or length of a spell of withdrawal from the labour force.In this paper we develop non‐parametric maximum likelihood estimators for the survivor functions of length of stay in a grade until leaving for a number of different possible destinations. Since the data are statistically incomplete, including right censored and left truncated durations, as well as complete durations, we must modify the competing risks theory in the biostatistical literature to take such incompleteness into account. Right censored durations arise when the individual is still in the grade when data collection ceases and left truncated durations when the individual is already in service when data collection commences.The competing risks model is fitted to data for Northern Ireland nursing service and used to predict staff flows between grades. We may thus estimate future movements within the system and predict the future manpower stocks.
Hierarchical production control of a flexible manufacturing system
Authors: Xie Xiao‐Lan 
Published: May 2007

AbstractA hierarchical production control framework for a flexible manufacturing system is proposed. The machines in the system are subject to failures in a wide spectrum band. At first, failures are clustered near some discrete points on the failure spectrum in order to define the hierarchical model. Each level in the hierarchy corresponds to a discrete point on the failure spectrum. At each level, faster varying failures are modelled by their mean behaviour, and more slowly varying failures are treated as static. Then, a hierarchical controller of multiple time scale type is proposed. System control at each level is based on the work of Kimemia and Gershwin. Simulation results conclude the paper.
Interaction between data analysis and telecommunications
Authors: Volle Michel 
Published: May 2007

AbstractWe consider interaction between data analysis and telecommunications from both sides, examining the contribution of each discipline to the other. The fast changes in telecommunications have some important consequences. First, the importance of statistics in the design of a network is growing, given the evolution of technology towards more digitalization and the resulting changes in dimensioning the network. Second, the technical tools of statistics are deeply modified, and there is concern about how to take this into account—particularly how to take advantage of the new economy of ‘value added services’ which uses the network as a ‘market place’.
On the numerical expansion of a second order stochastic process
Authors: Gutiérrez Ramón , Ruiz Juan Carlos , Valderrama Mariano J. 
Published: May 2007

AbstractThe utility of the classical Karhunen‐Loève expansion of a second order process is limited to its practical derivation, because it depends upon the solution of a Fredholm integral equation associated with it whose kernel is the covariance function of the process. So, in this paper we study two numerical procedures for solving such equations, the Rayleigh‐Ritz and the collocation methods, and also essay two different bases of L2‐orthogonal functions in order to perform the algorithms, Legendre polynomials and trigonometric functions, on two well‐known processes, the Wiener‐Lévy process and the Brownian‐bridge. The accuracy of the numerical results in relation to the real ones, as well as comparative studies among both procedures are also included.
Repairable failure‐delay systems with elementary structure
Authors: Limnios N. 
Published: May 2007

AbstractThis paper defines repairable failure‐delay systems, and gives explicit formulae for their availability. It presents models for single‐component, series and parallel systems with delay at system level, and a ‘rare event’ approximation for availability and reliability of series systems with delay at component level. Finally, it uses a renewal terminating process for deriving the limiting distribution of the lifetime of failure‐delay systems.
On the performance of peeling algorithms
Authors: Petitjean Michel , Saporta Gilbert 
Published: May 2007

AbstractThe peeling of a d‐dimensional set of points is usually performed with successive calls to a convex hull algorithm; the optimal worst‐case convex hull algorithm, known to have an O(n˙ Log (n)) execution time, may give an O(n˙n˙ Log (n)) to peel all the set; an O(n˙n) convex hull algorithm, m being the number of extremal points, is shown to peel every set with an O(n‐n) time, and proved to be optimal; an implementation of this algorithm is given for planar sets and spatial sets, but the latter give only an approximate O(n˙n) performance.
Clusterwise aggregation of relations: The case of paired comparisons of cognac ads
Authors: Owsinski Jan W. , Zadrożny Sławomir 
Published: May 2007

AbstractThis short paper takes up the problem stated by Gaul and Schader1 in 1988 of simultaneous clustering and aggregation of relations—in this case precedences (preferences)—so that aggregate preferences could represent relatively homogeneous groups of preference relations. The paper indicates the existence of two distinct questions, similar to those asked in the case of the global aggregation problem, regarding intra‐group agreement as to preferences represented in whatever form, and intra‐group agreement as to a common (‘regular’) preference. In both these cases, though, fundamental computational problems arise. This paper presents a heuristic for obtaining an approximate solution. Requirements as to the properly optimal method are outlined.
Embedded options in commercial banking and their impact on asset liability management
Authors: Boulier J. F. , Schoeffler P. 
Published: May 2007

AbstractCommercial bankers sell—more often give away—options to their clients like the prepayment facility attached to a mortgage or the right to obtain a credit at a prespecified interest rate which is associated in France with specific term deposits. This paper aims to present the financial consequences of these options from a microeconomic point of view and on the scale of the French banking system. We first example our valuation techniques and then analyse the impact on the balance sheet of a typical commercial bank, both in terms of value and sensitivity. Securitization is presented in this context as a way to monitor risk exposure. Finally the global impact of these embedded options in the French banking system is estimated and briefly discussed.
A dual strategy for the implementation of the aggregation principle in decision making under uncertainty
Authors: Rockafellar R. T. , Wets Roger J.‐B. 
Published: May 2007

AbstractA solution method for stochastic programs is proposed based on the aggregation principle, which allows one to find the solution of a stochastic program by aggregating the solutions of individual deterministic scenario problems. The method concentrates on finding good estimates of the dual variables associated with the non‐anticipativity constraints.
A continuous time markov‐renewal replacement model for manpower systems
Authors: Gerontidis Ioannis I. 
Published: May 2007

AbstractA continuous time Markov‐renewal model is presented that generalizes the classical Young and Almond model for manpower systems with given size. The construction is based on the associated Markov‐renewal replacement process and exploits the properties of the embedded replacement chain. The joint cumulant generating function of the grade sizes is derived and an asymptotic analysis provides conditions for these to converge in distribution to a multinominal random vector exponentially fast independently of the initial distribution, both for aperiodic and periodic embedded replacement chains. A regenerative approach to the wastage process is outlined and two numerical examples from the literature on manpower planning illustrate the theory.
Binary clustering with missing data
Authors: Nadif M. , Govaert G. 
Published: May 2007

AbstractA clustering method is presented for analysing multivariate binary data with missing values. When not all values are observed, Govaert3 has studied the relations between clustering methods and statistical models. The author has shown how the identification of a mixture of Bernoulli distributions with the same parameter for all clusters and for all variables corresponds to a clustering criterion which uses L1 distance characterizing the MNDBIN method (Marchetti8). He first generalized this model by selecting parameters which can depend on variables and finally by selecting parameters which can depend both on variables and on clusters. We use the previous models to derive a clustering method adapted to missing data. This method optimizes a criterion by a standard iterative partitioning algorithm which removes the necessity either to ignore objects or to substitute the missing data. We study several versions of this algorithm and, finally, a brief account is given of the application of this method to some simulated data.
Design of cellular manufacturing systems with refixturing and material handling considerations
Authors: Damodaran V. , Singh N. , Lashkari R. S. 
Published: May 2007

AbstractRefixturing and material handling aspects of cellular manufacturing systems are considered. For this purpose, two mathematical models are developed to determine machine groups and the assignment of part operations to machines. The first model is used simultaneously to assign operations of parts to machines and form machine groups. The second model is developed for the situation when new machines are procured for a cellular manufacturing environment. Examples are included to illustrate the applications of the models.
A scheduling algorithm for flexible flow lines with limited intermediate buffers
Authors: Sawik Tadeusz J. 
Published: May 2007

AbstractA new heuristic algorithm is proposed for scheduling a flexible flow line with limited in‐process buffers. The line is made up of a certain number of processing stages. Each stage has one or more identical parallel machines with limited buffers. Each part is processed by at most one machine in each stage. The problem objective is to minimize the makespan of the schedule for a set of part types selected for processing. The computational results for a set of test problems used in the literature are reported. In addition, the efficiency of the algorithm is tested on several groups of random problems.
A comprehensive approach of planning and scheduling based on petri nets
Authors: Harhalakis George , Proth Jean‐Marie , Xie Xiao‐Lan 
Published: May 2007

AbstractThe main results available on the use of black‐and‐white Petri nets for modelling, planning and scheduling manufacturing systems are presented. In the first part of the paper, the basics of Petri nets necessary to understand the subsequent presentation are introduced. Particular attention is paid to event graphs, a particular type of Petri nets used for modelling and evaluating ratio‐driven systems. The second part of the paper is devoted to ratio‐driven systems, their modelling and their scheduling. Job‐shops, assembly systems, and KANBAN systems are used to illustrate this section. Finally, the general case is investigated of manufacturing systems subject to changing demands. An approach based on conflict‐free Petri nets with input and output transitions is proposed for planning and scheduling this type of system.
Improving scoring techniques in banking applications
Authors: Perrodo Pascal 
Published: May 2007

AbstractScoring techniques are largely used today in banking applications, for marketing as well as risk assessment or control purposes. The most widely used method is Fisher's discriminatory analysis. We discuss here this method from a technical standpoint, showing its weaknesses and then propose a simpler and more general alternative. We first make an original presentation of the various scoring techniques and their basic principles. In particular, we provide a detailed description of Fisher's method, insisting on sensitive steps such as the discretization of continuous variables which is responsible for the nonlinearity of the model. We then go on to propose a new method that is completely linear and improves scoring performance. This technique is easy to explain, compute and use in real applications. Finally, we compare the performance of this new method with that of traditional techniques and of the more up‐to‐date neural nets method.
Minimax design of two‐state k‐out‐of‐n systems
Authors: Kouikoglou Vassilis S. , Phillis Yannis A. 
Published: May 2007

AbstractThe optimal size of k is specified for two‐state k‐out‐of‐n systems that may be functioning or fail in either state. It is assumed that the steady‐state, success and failure probabilities are not known exactly. The problem is reduced to finding the saddle‐point solution to a minimax optimization problem. An example shows that the minimax design is robust with regard to uncertainty.