bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two queues in series with a finite, intermediate waitingroom
Authors: Neuts Marcel F. 
Published: April 2006

A service unit I, with Poisson input and general service times is in series with a unit II, with negative-exponential service times. The intermediate waitingroom can accomodate at most k persons and a customer cannot leave unit I when the waitingroom is full.The paper shows that this system of queues can be studied in terms of an imbedded semi-Markov process. Equations for the time dependent distributions are given, but the main emphasis of the paper is on the equilibrium conditions and on asymptotic results.
Use of erlangian distributions for single-server queueing systems
Authors: Kotiah T. C. T. , Thompson J. W. , Waugh W. A. O'N. 
Published: April 2006

SummaryThe use of Erlangian distributions has been proposed for the approximation of more general types of distributions of interarrival and service times in single-server queueing systems. Any Erlangian approximation should have the same mean and variance as the distribution it approximates, but it is not obvious what effect the various possible approximants have on the behaviour of the system. A major difference between approximants is their degree of skewness and accordingly, numerical results for various approximants are obtained for (a) the mean time spent by a customer in a simple single-server system, and (b) the mean queue length in a system with bulk service. Skewness is shown to have little effect on these quantities.
Selective interaction of two independent recurrent processes
Authors: Hoopen M. Ten , Reuver H. A. 
Published: April 2006

SummaryConsidered are two mutually independent recurrent processes each consisting of a time series of unitary stimuli. The durations of the intervals between the stimuli in each series are independent of each other and identically distributed with probability density functions φ (t) and ψ (t). Every stimulus of the ψ (t) process annihilates the next stimulus of the φ (t) process. The probability density function of the intervals of the transformed φ (t) process is derived for the case where either the φ (t) or the ψ (t) process is Poisson.
Physical nearest-neighbour models and non-linear time-series. II Further discussion of approximate solutions and exact equations
Authors: Bartlett M. S. 
Published: April 2006

The approximate two- and three-dimensional solutions for spatial correlations, using the non-linear time-series approach for nearest-neighbour systems developed in my previous paper, are further discussed.Orthogonal expansions for the correlation functions are also developed which determine with this approach, though so far only in principle, the exact solutions.
Optimal replacement with semi-Markov shock models
Authors: Feldman Richard M. 
Published: April 2006

Consider a system that is subject to a sequence of randomly occurring shocks; each shock causes some damage of random magnitude to the system. Any of the shocks might cause the system to fail, and the probability of such a failure is a function of the sum of the magnitudes of damage caused from all previous shocks.The purpose of this paper is to derive the optimal replacement rule for such a system whose cumulative damage process is a semi-Markov process. This allows for both the time between shocks and the damage due to the next shock to be dependent on the present cumulative damage level.Only policies within the class of control-limit policies will be considered; namely, policies with which no action is taken if the damage is below a fixed level, and a replacement is made if the damage is above that.An example will be given illustrating the use of the optimal replacement rule.
On the distribution of records in a finite sequence of observations, with an application to a road traffic problem
Authors: Haghighi-Talab Dariush , Wright Christopher 
Published: April 2006

Probability distributions relating to the number and positions of lower records in a finite sequence of observations are obtained by methods involving the permutation of ranks. Some new results, and results of earlier authors, are expressed in a form thought to be useful for direct practical applications.Expressions are also given for the distribution of the length of a ‘record run’, which consists of the observations following and including a given record either up to the next record, or, if a further record does not occur, up to the end of the sequence of observations. This quantity, whose distribution is closely related to that of the inter-record time, has a direct and simple application to road traffic leaving a signal which has been confirmed by experimental observation.
Convex majorization with an application to the length of critical paths
Authors: Meilijson Isaac , Nádas Arthur 
Published: April 2006

1. (Y) for all non-negative, non-decreasing convex functions φ (X is convexly smaller than Y) if and only if, for all .2.Let H be the Hardy–Littlewood maximal function HY(x) = E(Y – X | Y > x). Then HY(Y) is the smallest random variable exceeding stochastically all random variables convexly smaller than Y.3.Let X1X2 · ·· Xn be random variables with given marginal distributions, let I1,I2, ···, Ik be arbitrary non-empty subsets of {1,2, ···, n} and let M = max (M is the completion time of a PERT network with paths Ij, and delay times Xi.) The paper introduces a computation of the convex supremum of M in the class of all joint distributions of the Xi's with specified marginals, and of the ‘bottleneck probability' of each path.
Strategy stability in complex randomly mating diploid populations
Authors: Hines W. G. S. 
Published: April 2006

A class of Lyapunov functions is used to demonstrate that strategy stability occurs in complex randomly mating diploid populations. Strategies close to the evolutionarily stable strategy tend to fare better than more remote strategies. If convergence in mean strategy to an evolutionarily stable strategy is not possible, evolution will continue until all strategies in use lie on a unique face of the convex hull of available strategies.The results obtained are also relevant to the haploid parthenogenetic case.
On the best order of observation in optimal stopping problems
Authors: Gilat David 
Published: April 2006

For optimal stopping problems in which the player is allowed to choose the order of the random variables as well as the stopping rule, a notion of order equivalence is introduced. It is shown that different (non-degenerate) distributions cannot be order-equivalent.This result unifies and generalizes two theorems of a similar nature recently obtained by Hill and Hordijk (1985).
Invariant measures for Markov chains with no irreducibility assumptions
Authors: Tweedie R. L. 
Published: April 2006

Foster's criterion for positive recurrence of irreducible countable space Markov chains is one of the oldest tools in applied probability theory. In various papers in JAP and AAP it has been shown that, under extensions of irreducibility such asϕ-irreducibility, analogues of and generalizations of Foster's criterion give conditions for the existence of an invariant measureπfor general space chains, and forπto have a finitef-moment ∫π (dy)f(y), wherefis a general function. In the casef≡ 1 these cover the question of finiteness ofπitself.In this paper we show that the same conditions imply the same conclusionswithout any irreducibility assumptions; Foster's criterion forces sufficient and appropriate regularity on the space automatically. The proofs involve detailed consideration of the structure of the minimal subinvariant measures of the chain.The results are applied to random coefficient autoregressive processes in order to illustrate the need to remove irreducibility conditions if possible.
Stochastic scrabble: large deviations for sequences with scores
Authors: Arratia Richard , Morris Pricilla , Waterman Michael S. 
Published: April 2006

A derivation of a law of large numbers for the highest-scoring matching subsequence is given. Let Xk, Yk be i.i.d. q=(q(i))i∊S letters from a finite alphabet S and v=(v(i))i∊S be a sequence of non-negative real numbers assigned to the letters of S. Using a scoring system similar to that of the game Scrabble, the score of a word w=i1 · ·· im is defined to be V(w)=v(i1) + · ·· + v(im). Let Vn denote the value of the highest-scoring matching contiguous subsequence between X1X2 · ·· Xn and Y1Y2· ·· Yn. In this paper, we show that Vn/K log(n) → 1 a.s. where K ≡ K(q,v). The method employed here involves ‘stuttering’ the letters to construct a Markov chain and applying previous results for the length of the longest matching subsequence. An explicit form for β ∊Pr(S), where β (i) denotes the proportion of letter i found in the highest-scoring word, is given. A similar treatment for Markov chains is also included.Implicit in these results is a large-deviation result for the additive functional, H ≡ Σn < τv(Xn), for a Markov chain stopped at the hitting time τ of some state. We give this large deviation result explicitly, for Markov chains in discrete time and in continuous time.
A comparison of the ordinary and a varying parameter exponential smoothing
Authors: Bonsdorff Heikki 
Published: April 2006

An adaptive-type exponential smoothing, motivated by an insurance tariff problem, is treated. We consider the processZn=ß(Zn –1)Xn+(1 –ß(Zn–1))Zn–1, whereXnare i.i.d. taking values in the interval [0,M],M≦ ∞ andßis a monotonically increasing function [0,M] → [c,d], 0 <c<d< 1.Together with (Zn), we consider the ordinary exponential smoothingYn=αXn+ (1 –α)Yn –1whereαis a constant, 0 <α< 1. We show that (Yn) and (Zn) are geometrically ergodic Markov chains (in the case of finite interval we even have uniform ergodicity) and thatEYn, EZnconverge to limitsEY, EZ,respectively, with a geometric convergence rate. Moreover, we show thatEzis strictly less thanEY=EXn.
Nested Monte Carlo study of random packing on the sphere
Authors: Rodgers R. P. C. , Baddeley A. J. 
Published: April 2006

We consider two random sequential packing processes in which spheres of unit radius are randomly attached to the surface of a fixed unit sphere. Independent random spheres are generated and added successively, provided there is no overlap with previous spheres. In model 1, the process stops when a trial sphere intersects one of the previously-accepted spheres. In model 2, random sequential packing, any such overlapping trial sphere is discarded and the next random sphere is tried, until it is impossible to add any further spheres.Previous workers have conjectured convincingly that no exact analytical solution is possible for this type of problem. We use Monte Carlo simulation methods to estimate transition probabilities for the two models. Because some probabilities are extremely small, a simulation using independent repetitions of the model would be inefficient. We designed a branching process of conditionally binomial trials, and performed over 108 trials on a supercomputer.
Optimal stationary strategies in leavable Markov decision processes
Authors: Fassbender Matthias 
Published: April 2006

This paper establishes the existence of an optimal stationary strategy in a leavable Markov decision process with countable state space and undiscounted total reward criterion.Besides assumptions of boundedness and continuity, an assumption is imposed on the model which demands the continuity of the mean recurrence times on a subset of the stationary strategies, the so-called ‘good strategies'. For practical applications it is important that this assumption is implied by an assumption about the cost structure and the transition probabilities. In the last part we point out that our results in general cannot be deduced from related works on bias-optimality by Dekker and Hordijk, Wijngaard or Mann.
A closure characterisation of phase-type distributions
Authors: Maier Robert S. , O'Cinneide Colm Art 
Published: April 2006

We characterise the classes of continuous and discrete phase-type distributions in the following way. They are known to be closed under convolutions, mixtures, and the unary ‘geometric mixture' operation. We show that the continuous class is the smallest family of distributions that is closed under these operations and contains all exponential distributions and the point mass at zero. An analogous result holds for the discrete class.We also show that discrete phase-type distributions can be regarded as ℝ+-rational sequences, in the sense of automata theory. This allows us to view our characterisation of them as a corollary of the Kleene–Schützenberger theorem on the behavior of finite automata. We prove moreover that any summable ℝ+-rational sequence is proportional to a discrete phase-type distribution.
A Highly Sensitive Hybrid Colorimetric and Fluorometric Molecular Probe for Cyanide Sensing Based on a Subphthalocyanine Dye
Authors: Palomares E. , Martínez‐Díaz M. V. , Torres T. , Coronado E. 
Published: April 2006

AbstractA highly sensitive, selective colorimetric and fluorometric molecular probe based on a subphthalocyanine dye has been developed for cyanide‐anion determination in aqueous solution. It has also been shown that a carboxysubphthalocyanine derivative can be covalently anchored to transparent mesoporous nanocrystalline high‐surface‐area metal oxide films to detect low concentrations of cyanide anion in pure water with no interference from other anionic or cationic species.
Growing Metal Nanoparticles by Enzymes
Authors: Willner I. , Baron R. , Willner B. 
Published: April 2006

AbstractEnzymes act as catalysts for the growth of metallic nanoparticles (NPs). The enzyme‐mediated growth of metallic NPs provides a general means to follow biocatalyzed transformations, and to develop optical sensors for different substrates such as glucose, L‐DOPA, alcohols, lactate or nerve gas analogs. Enzymes modified with Au NPs act as biocatalysts for the fabrication of metallic nanowires. The dip‐pen nanolithography of NP‐functionalized enzymes on Si surfaces yields biocatalytic templates that enable the orthogonal evolution of nanowires consisting of different metals.
New unbiased symmetric metrics for evaluation of air quality models
Authors: Yu Shaocai , Eder Brian , Dennis Robin , Chu Shao‐Hang , Schwartz Stephen E. 
Published: April 2006

AbstractUnbiased symmetric metrics to quantify the relative bias and error between modeled and observed concentrations, based on the factor between measured and observed concentrations, are introduced and compared to conventionally employed metrics. Application to the evaluation of several data sets shows that the new metrics overcome concerns with the conventional metrics and provide useful measures of model performance. Copyright © 2006 Royal Meteorological Society
Chirality as an inherent general property of matter
Authors: Davankov Vadim 
Published: April 2006

AbstractA statement has been formulated that chirality is an indispensable inherent property of all material objects, at one level of organization of matter or another. The translation of chirality from one level of material objects to another deserves our attention. The parity violation of weak interactions can be discussed in terms of the homochirality of the pool of fundamental particles, as it translates into optical activity of metal vapors. Individual photons and energy quanta are considered to be chiral entities, too, since they can be separated into beams of circularly polarized radiation. The chiral structure of the universe has been proposed and a method of determining the orientation of the axis of rotation of the universe suggested. Chirality 18:459–461, 2006. © 2006 Wiley‐Liss, Inc.
Synthesis, chiral HPLC resolution and configuration assignment of 1‐phenylglyceryl trinitrate stereomers
Authors: Chegaev Konstantin , Lazzarato Loretta , Tron Gian Cesare , Marabello Domenica , Stilo Antonella Di , Cena Clara , Fruttero Roberta , Gasco Alberto , Vanthuyne Nicolas , Roussel Christian 
Published: April 2006

AbstractAs an introductory study of in vitro vasodilating activity, the access to the four stereomers of 1‐phenylglyceryl trinitrate is described using achiral and chiral chromatography. For semi‐preparative separation of the enantiomers, a Chiralcel OD (250 × 10 mm, 10 μm) was used. Catalytic reduction leading to the corresponding stereomers of 1‐phenylglycerol allowed absolute configuration assignments. The same methods were used for the separation and configuration assignment of the enantiomers of 3‐phenylpropane‐1,2‐diyl dinitrate. Chirality, 2006. © 2006 Wiley‐Liss, Inc.
Restriction landmark genome scanning method using isoschizomers (MspI/HpaII) for DNA methylation analysis
Authors: Takamiya Tomoko , Hosobuchi Saeko , Asai Kenji , Nakamura Eiji , Tomioka Keisuke , Kawase Makoto , Kakutani Tetsuji , Paterson Andrew H. , Murakami Yasufumi , Okuizumi Hisato 
Published: April 2006

AbstractRestriction landmark genome scanning (RLGS) is a 2‐DE of genomic DNA, which visualizes thousands of loci. In a conventional RLGS method for methylation analysis, we have used a methylation sensitive restriction enzyme, NotI as a landmark. However, it was unable to discriminate methylation polymorphism from sequence polymorphism. Here, we report an improved RLGS method to detect methylated sites directly. We employed isoschizomers, MspI and HpaII, that recognize the same sequence (CCGG) but have different methylation sensitivity. We carried out the RLGS analysis of Arabidopsis thaliana ecotype Columbia, and obtained a pair of spot patterns with MspI and HpaII. We detected 22 spots in both patterns. In comparison of them, 18% of the spots were polymorphic, which indicated the methylation of C5mCGG sites. Further analyses revealed an additional methylated site of NotI. Moreover, 52 and 54 restriction enzyme sites were also analyzed in two other ecotypes, Wassilewskija and Landsberg erecta, respectively. Consequently, 15% of the 52 common sites showed methylation polymorphism among the three ecotypes. The restriction sites analyzed in this study were located in or near genes, and contribute new data about the correlation between methylation status and gene expression. Therefore, this result strongly indicates that the improved RLGS method is readily applicable to practical analyses of methylation dynamics, and provides clues to the relationship between methylation and gene expression.
Simulation of groundwater dynamics in the North China Plain by coupled hydrology and agricultural models
Authors: Nakayama Tadanobu , Yang Yonghui , Watanabe Masataka , Zhang Xiying 
Published: April 2006

AbstractWe simulated the effects of irrigation on groundwater flow dynamics in the North China Plain by coupling the NIES Integrated Catchment‐based Ecohydrology (NICE) model with DSSAT‐wheat and DSSAT‐maize, two agricultural models. This combined model (NICE‐AGR) was applied to the Hai River catchment and the lower reach of the Yellow River (530 km wide by 840 km long) at a resolution of 5 km. It reproduced excellently the soil moisture, evapotranspiration and crop production of summer maize and winter wheat, correctly estimating crop water use. So, the spatial distribution of crop water use was reasonably estimated at daily steps in the simulation area. In particular, NICE‐AGR reproduced groundwater levels better than the use of statistical water use data. This indicates that NICE‐AGR does not need detailed statistical data on water use, making it very powerful for evaluating and estimating the water dynamics of catchments with little statistical data on seasonal water use. Furthermore, the simulation reproduced the spatial distribution of groundwater level in 1987 and 1988 in the Hebei Plain, showing a major reduction of groundwater level due mainly to overpumping for irrigation. Copyright © 2006 John Wiley & Sons, Ltd.
Effectiveness of three post‐fire rehabilitation treatments in the Colorado Front Range
Authors: Wagenbrenner J. W. , MacDonald L. H. , Rough D. 
Published: April 2006

AbstractPost‐fire rehabilitation treatments are commonly implemented after high‐severity wildfires, but few data are available about the efficacy of these treatments. This study assessed post‐fire erosion rates and the effectiveness of seeding, straw mulching, and contour felling in reducing erosion after a June 2000 wildfire northwest of Loveland, Colorado. Site characteristics and sediment yields were measured on 12 burned and untreated control plots and 22 burned and treated plots from 2000 to 2003. The size of the hillslope plots ranged from 0·015 to 0·86 ha.Sediment yields varied significantly by treatment and were most closely correlated with the amount of ground cover. On the control plots the mean sediment yield declined from 6–10 Mg ha−1in the first two years after burning to 1·2 Mg ha−1in 2002 and 0·7 Mg ha−1in 2003. Natural regrowth caused the amount of ground cover on the control plots to increase progressively from 33% in fall 2000 to 88% in fall 2003. Seeding had no effect on either the amount of ground cover or sediment yields. Mulching reduced sediment yields by at least 95% relative to the control plots in 2001, 2002, and 2003, and the lower sediment yields are attributed to an immediate increase in the amount of ground cover in the mulched plots. The contour‐felling treatments varied considerably in the quality of installation, and sediment storage capacities ranged from 7 to 32 m3ha−1. The initial contour‐felling treatment did not reduce sediment yields when subjected to a very large storm event, but sediment yields were significantly reduced by a contour‐felling treatment installed after this large storm. The results indicate that contour felling may be able to store much of the sediment generated in an average year, but will not reduce sediment yields from larger storms. Copyright © 2006 John Wiley & Sons, Ltd.
Cytotoxicity and altered c‐myc gene expression by medical polyacrylamide hydrogel
Authors: Xi T.F. , Fan C.X. , Feng X.M. , Wan Z.Y. , Wang C.R. , Chou L.L. 
Published: April 2006

AbstractMedical Polyacrylamide Hydrogel (PAMG)has been used in plastic and aesthetic surgery for years. However, its safety is still in doubt in many countries. In the current research, first an approach, using high performance liquid chromatography (HPLC), to determine the amount of residual acrylamide monomer (AM) in the PAMG was presented. Then the cytotoxicity of PAMG was investigated using cell counting and methyl thiazolyl tetrazolium (MTT) assay. To explore the mechanism of this toxicity, normal human fibroblasts cultured in medium extracts were analyzed. Membrane changes and other related parameters were investigated using flow cytometry (FCM). Real time fluorescent polymerase chain reaction (real time PCR) was also introduced to determine the biological response of the fibroblasts. During this process, three representative genes (p53, β‐actin, and c‐myc, which are tumor suppressor genes, housekeeping genes, and proto‐oncogenes respectively) were selected for examination. Results indicated that a method based on HPLC is practical and simple for determining AM in PAMG. The detection limits can reach the desired ppb level, and so it can fully meet the requirements of the studies of PAMG. Polyacylamide Hydrogel inhibits the growth of human fibroblasts and may cause the apoptosis of human fibroblasts. Moreover, it can alter physical parameters such as the size and the granularity of these cells. Furthermore, these three genes have a relatively typical amplification plot and highly related, wide‐range standard curves, and so this reaction system is definitely suitable for the semiquantification of these genes. PAMG induces the increase of the message ribonucleic acid (mRNA) expression of c‐myc, while the p53 and β‐actin remain even. This change is not related to the concentration of AM in the gel and may be incited by other components in the extract of PMAG. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006