bluuebunny/crossref_metadata_2025 huggingface dataset:
On the relation between types and tokens in literary text
Authors: Brainerd Barron
Published: April 2006

The ratio of the number Xn of different words (types) in a text of length n (token) words to n has received considerable attention in the literature of statistical linguistics. The present note contains two stochastic models for Xn based on an inhomogeneous discrete Markov process of the pure birth type where the transition probabilities take certain forms depending only upon n. These models are then tested against data obtained from the plays of William Shakespeare.
Moments of age and remaining life in renewal processes
Authors: Katz S. , Naor P. , Shinnar R.
Published: April 2006

Expressions are developed for the moments of age and remaining life in renewal processes, and from them, expressions for the moments of the last and next renewal epochs. The results for remaining life and next renewal epoch may be regarded as generalizations of theorems of Wald (1944) and others. The results for age and last renewal epoch do not fit into this sequential analysis framework. Both sets of results are obtained from partial differential equations developed for the distributions of age and of remaining life. These partial differential equations are of the “conservation” type familiar from statistical mechanics, and may have some independent interest for renewal theory.
An application of the minimum discrimination information estimate to compute log-likelihood ratios
Authors: Melnick E. L. , Kullback S.
Published: April 2006

In this paper the minimum discrimination information estimate is used to compute the log-likelihood ratio or logarithm of the Radon-Nikodym derivative In (dP1/dP2) when the stochastic process {x(t), t∈T) has either the probability measure P1 or P2. One example tests the mean value function of Gaussian processes. The other tests the mean value function of a continuous time Poisson process.
Limit theorems for processes such as the Markov branching process
Authors: Barbour Andrew D.
Published: April 2006

Let X(t) be a continuous time Markov process on the integers such that, if σ is a time at which X makes a jump, X(σ)– X(σ–) is distributed independently of X(σ–), and has finite mean μ and variance. Let q(j) denote the residence time parameter for the state j. If tn denotes the time of the nth jump and Xn ≡ X(tb), it is easy to deduce limit theorems for
from those for sums of independent identically distributed random variables. In this paper, it is shown how, for μ > 0 and for suitable q(·), these theorems can be translated into limit theorems for X(t), by using the continuous mapping theorem.
Some remarks on a counter process
Authors: Takács Lajos
Published: April 2006

In 1968 Lampard determined some limit distributions for a counter process in which the input and output are independent Poisson processes. In 1974 Phatarfod dealt with the generalizations of Lampard's formulas for the case when the input and output form a bivariate Poisson process; however, his reasoning is erroneous. The object of this paper is to determine the correct limit distributions for the generalized process.
The exponential rate of convergence of the distribution of the maximum of a random walk. Part II
Authors: Veraverbeke N. , Teugels J. L.
Published: April 2006

Let Gn (x) be the distribution of the nth successive maximum of a random walk on the real line. Under conditions typical for complete exponential convergence, the decay of Gn (x) – limn→∞ Gn(x) is asymptotically equal to H(x) γn n–3/2 as n → ∞where γ < 1 and H(x) a function solely depending on x. For the case of drift to + ∞, G∞(x) = 0 and the result is new; for drift to – ∞we give a new proof, simplifying and correcting an earlier version in [9].
Success runs in a two-state Markov chain
Authors: Rajarshi M. B.
Published: April 2006

Success runs of a fixed length in a two-state Markov chain are discussed. The results are analogous to those in the case of independent Bernoulli trials. The generating function of the waiting time for the first occurrence of a success run is obtained from the theory of recurrent events. Under certain conditions, the distribution of the number of long runs in a large number of trials is shown to be Poisson.
A two-dimensional random walk in the presence of a partially reflecting barrier
Authors: Cressie Noel
Published: April 2006

A general two-dimensional random walk is considered with a barrier along the y-axis. Absorption probabilities are derived when the barrier is absorbing, and when it is semi-reflecting.
General solidarity theorems for semi-Markov processes
Authors: Cheong Choong K. , Teugels Jozef L.
Published: April 2006

Let {Zt, t ≧ 0} be an irreducible regular semi-Markov process with transition probabilities Pij (t). Let f(t) be non-negative and non-decreasing to infinity, and let λ ≧ 0. This paper identifies a large set of functions f(t) with the solidarity property that convergence of the integral ≧ eλtf(t)Pij(t) dt for a specific pair of states i and j implies convergence of the integral for all pairs of states. Similar results are derived for the Markov renewal functions Mij (t). Among others it is shown that f(t) can be taken regularly varying.
Characterization of certain populations by independence of order statistics
Authors: Galambos János
Published: April 2006

A method, making use of characteristic functions, is presented to prove theorems on characterization of distributions by independence of order statistics. Since exact independence in practice is rarely achieved, much attention is being given in the literature to theorems on determining the distributions for which certain statistics are ‘almost’ independent. The technique of this new line of investigation is strongly dependent on the fact that for the case of exact independence there is a solution in terms of characteristic functions. The present work was guided by this fact. In addition to the new method, Theorem 2 appears to be new.
On queues involving batches
Authors: Mohanty S. G.
Published: April 2006

It has been demonstrated by Takács in a series of papers and in his book that combinatorial methods can be successfully applied to derive certain probability distributions in queueing processes. In this paper, we further illustrate the usefulness of combinatorial techniques and determine the stochastic law of the busy period in two queueing systems particularly involving batches. It may be of interest to note that queues involving batches have been dealt with in [3] and [7].
The distribution of the maximum Brownian excursion
Authors: Kennedy Douglas P.
Published: April 2006

The distribution of the maximum of the unsigned scaled Brownian excursion process and of a modification of that process are derived. These distributions are related to the one-dimensional Brownian bridge.
Recurrence times of draft-patterns from reservoirs
Authors: Pegram G. G. S.
Published: April 2006

Expressions for the mean and variance of the recurrence time of non-overlapping draft-patterns of draft from a Moran Reservoir Model (discrete-state and discrete-time Markov chain) are derived using Feller's Renewal argument. In addition an expression for the mean recurrence time for self-overlapping patterns of draft is derived using run-theory.
On search for a Brownian target
Authors: Corwin Thomas L.
Published: April 2006

A target is assumed to move according to a Wiener process in ℝ1. The probability of detecting the target is computed in terms of the search effort which accumulates along the target's path. Under certain independence assumptions this probability is given by the expectation of an exponential functional of the process. It is shown in this note that the failure probability in a search for a Wiener target is asymptotically proportional to , where T is the accumulated time spent searching. The asymptotic failure probability is also shown to be independent of the position of the search in ℝ1. In a similar fashion, it is shown that the failure probability in a search for a Wiener target in ℝ2 is independent of the position of the search and asymptotically proportional to (c log T + l)–1, c >0
A diffusion process model for the optimal investment strategies of an R & D project
Authors: Zuckerman Dror
Published: April 2006

In this article we examine an R & D project in which the project status changes according to a diffusion process. The decision variables include a resource expenditure strategy and a stopping policy which determines when the project should be terminated. The drift and the diffusion parameters of the project status process are assumed to be functions of the resource expenditure rate.

The terminal reward from the project is a non-decreasing function of the project status. Our purpose is to select optimal investment strategies under the discounted return criterion.

The value of the project is shown to be a solution of a second order, non-linear differential equation. Finally, we derive the optimal investment strategies for an R & D project in which the project status changes according to a non-homogeneous compound Poisson process by using diffusion approximation.
Clumping effects in models of isolation by distance
Authors: Sudbury Aidan
Published: April 2006

Individuals situated on the infinite line breed and produce offspring that independently migrate a distance that is a random variable depending on the number in each family. It is shown that under very general conditions the individuals in the nth generation will tend to form clumps.
A useful random time-scale transformation for the standard epidemic model
Authors: Watson Ray
Published: April 2006

In this paper it is shown that a random time-scale transformation leads to a simple derivation of some asymptotic results describing the progress of a major outbreak in the standard epidemic model. These results find application in approximation of the size distribution and in estimation of the threshold parameter.
The lifetime of a standby system of units having the Birnbaum and Saunders distribution
Authors: Raaijmakers F. J. M.
Published: April 2006

In this paper a formula is derived for the probability density function of the lifetime for a system of identical units. The lifetime of the system is the sum of the lifetimes of the independent units when the units have lifetimes distributed independently by the law proposed by Birnbaum and Saunders (1969).
Random secants of a convex body generated by surface randomness
Authors: Ehlers P. Frank , Enns Ernest G.
Published: April 2006

Length distributions for random secants through a convex region K are derived for three types of randomness. The results are formulated in terms of geometric properties of K, e.g. the overlap surface content of K with its translated self. The distribution of distance between two random points in K, expressed in terms of the overlap volume, is shown to extend to non-convex (including disjoint) regions.
Series expansions of probability generating functions and bounds for the extinction probability of a branching process
Authors: Daley D. J. , Narayan Prakash
Published: April 2006

In the Taylor series expansion about s = 1 of the probability generating function f(s) of a non-negative integer-valued random variable with finite nth factorial moment the remainder term is proportional to another p.g.f. This leads to simple proofs of other power series expansions for p.g.f.'s, including an inversion formula giving the distribution in terms of the moments (when this can be done). Old and new inequalities for the extinction probability of a branching process are established.
Random paths through a convex region
Authors: Enns E. G. , Ehlers P. F.
Published: April 2006

The distribution of the length of random secants through a convex region is formulated in terms of the intersection volume of the convex region with its translated self. This method allows a more straightforward approach to calculating secant-length distributions for various measures of randomness. The results are applied to calculating the transit-time distribution of particles traversing a convex region. Several examples are given.
A hide–search game
Authors: Subelman Eduardo J.
Published: April 2006

We consider a game in which one player hides a ball in one of n boxes and the other player is allowed to search for it. There are known probabilities that the searcher will overlook the ball if he searches the correct box. The hider wishes to minimize and the searcher to maximize the probability that the ball will be found in m or fewer searches. We exhibit a procedure which allows efficient computation of optimal strategies for both players without solving the game as a linear program. The results are extended to a non-zero-sum game where the searcher's objective is to minimize the expected time until the ball is found.
Simpler proofs of two threshold theorems for a general stochastic epidemic
Authors: Rajarshi M. B.
Published: April 2006

We give here fairly elementary proofs for the threshold theorems due to Williams (1971) and Whittle (1955). Our proofs are based on an application of the reflection principle through the ballot problem and the exact distribution of the size of the epidemic as derived by Foster (1955). Williams's threshold theorem is extended to an epidemic with multiple introduction of cases.
The determination of the age of a clone from characteristics of its geographical distribution
Authors: An Sudbury Aid , Clifford Peter
Published: April 2006

Each point with integer coordinates in d dimensions is occupied by one individual. These individuals produce offspring at a Poisson rate 1, and these offspring migrate and displace other individuals. With probability u (the mutation rate) an offspring is of an entirely new type. A number of points N0 will be occupied by the same type as the individual at the origin. It is shown that the distribution of N0 arising from an ancient mutation does not differ greatly from the distribution of N0 when the mutation is recent. However, the geographical spread is shown to be important, and a central limit theorem is proved for the age of the mutant clone given that a representative is present at a large distance from the origin.
Random collision models in oriented graphs
Authors: Itoh Yoshiaki
Published: April 2006

We investigate a random collision model for competition between types of individuals in a population. There are dominance relations defined for each pair of types such that if two individuals of different types collide then after the collision both are of the dominant type. These dominance relations are represented by an oriented graph, called a tournament. It is shown that tournaments having a particular form are relatively stable, while other tournaments are relatively unstable. A measure of the stability of the stable tournaments is given in the main theorem.
An explicit upper bound for the mean busy period in a GI/G/1 queue
Authors: Loulou Richard
Published: April 2006

In this paper, an upper bound is derived for the mean busy cycle duration in GI/G/1 queues. The bound is of the form A/(1 – ρ), where ρ is the traffic intensity and A involves three moments of the basic random variables of the queue. The proof uses a well-known result of random walk theory.
A characterization of the uniform distribution on the circle in the analysis of directional data
Authors: Bingham M. S.
Published: April 2006

It was conjectured some time ago by K. V. Mardia that if, for random samples of some fixed size N ≧ 2 from a given non-degenerate circular population, the sample mean direction and the sample resultant length are independently distributed, then the population must be uniformly distributed round the circle. In this paper it is shown that, apart from one minor exception, Mardia's conjecture is true in the case N = 2. No regularity conditions are necessary for the proof. The same problem has been studied, subject to regularity conditions, by Kent, Mardia and Rao (1976) for all sample sizes N ≧ 2 except N = 4.
Limit laws for the maxima of a class of quasi-stationary sequences
Authors: Turkman K. F. , Walker A. M.
Published: April 2006

A class of quasi-stationary sequences of random variables is introduced. After giving the definition, it is shown that the limiting distributions of the maxima of such sequences, when suitably normalized, converge to one of the three extreme-value distributions.
Proportional intensities and strong ergodicity for Markov processes
Authors: Scott Mark , Isaacson Dean L.
Published: April 2006

By assuming the proportionality of the intensity functions at each time point for a continuous-time non-homogeneous Markov process, strong ergodicity for the process is determined through strong ergodicity of a related discrete-time Markov process. For processes having proportional intensities, strong ergodicity implies having the limiting matrix L satisfy L · P(s, t) = L, where P(s, t) is the matrix of transition functions.
R&D projects analyzed by semimartingale methods
Authors: Aase Knut K.
Published: April 2006

In this article we examine R&D projects where the project status changes according to a general dynamic stochastic equation. This allows for both continuous and jump behavior of the project status. The time parameter is continuous. The decision variable includes a non-stationary resource expenditure strategy and a stopping policy which determines when the project should be terminated. Characterization of stationary policies becomes straightforward in the present setting. A non-linear equation is determined for the expected discounted return from the project. This equation, which is of a very general nature, has been considered in certain special cases, where it becomes manageable. The examples include situations where the project status changes according to a compound Poisson process, a geometric Brownian motion, and a Brownian motion with drift. In those cases we demonstrate how the exact solution can be obtained and the optimal policy found.
An optimal sequential policy for controlling a Markov renewal process
Authors: McNamara J. M.
Published: April 2006

This paper discusses a renewal process whose time development between renewals is described by a Markov process. The process may be controlled by choosing the times at which renewal occurs, the objective of the control being to maximise the long-term average rate of reward. Let γ ∗ denote the maximum achievable rate. We consider a specific policy in which a sequence of estimates of γ ∗ is made. This sequence is defined inductively as follows. Initially an (a priori)estimate γo is chosen. On making the nth renewal one estimates γ ∗ in terms of γo, the total rewards obtained in the first n renewal cycles and the total length of these cycles. γ n then determines the length of the (n + 1)th cycle. It is shown that γ n tends to γ ∗ as n tends to∞, and that this policy is optimal.

The time at which the (n + 1)th renewal is made is determined by solving a stopping problem for the Markov process with continuation cost γ n per unit time and stopping reward equal to the renewal reward. Thus, in general, implementation of this policy requires a knowledge of the transition probabilities of the Markov process. An example is presented in which one needs to know essentially nothing about the details of this process or the fine details of the reward structure in order to implement the policy. The example is based on a problem in biology.
Parameter values of ARMA models minimising the one-step-ahead prediction error when the true system is not in the model set
Authors: Kabaila Paul
Published: April 2006

In This paper we answer the following question. Is there any a priori reason for supposing that there is no more than one set of ARMA model parameters minimising the one-step-ahead prediction error when the true system is not in the model set?
On the moments of the cumulative idle time in an M/D/∞ queue
Authors: Foley R. D. , Yadin M.
Published: April 2006

Let I denote the fraction of time that an M/D/∞ queue is idle during [0, t]. We give a simple proof that the nth moment of I conditioned on k arrivals equals the kth moment of I conditioned on n arrivals.
A note on the recurrence of a correlated random walk
Authors: Henderson Robin , Renshaw Eric , Ford David
Published: April 2006

A non-analytical proof of recurrence is obtained via an embedding procedure for a two-dimensional correlated lattice random walk.
Reordering heuristics for routing in communications networks
Authors: Topkis Donald M.
Published: April 2006

Move-to-front and move-to-back heuristics are considered for adaptively reordering routing tables in communications networks. Limiting properties are established for Markov chain models of these heuristics. The limiting distributions of the number of path attempts per call for the two heuristics and for a fixed random permutation are stochastically ordered.
The M/M/∞ queue in a random environment
Authors: O'Cinneide C. A. , Purdue P.
Published: April 2006

The M/M/∞ queue in a random environment is an infinite-server queue where arrival and service rates are stochastic processes. Here we study the steady-state behavior of such a system. Explicit results are obtained for the factorial moments, the impossibility of a ‘matrix-Poisson' steady-state distribution is demonstrated and two numerical examples are presented.
Characterization of the logistic and loglogistic distributions by extreme value related stability with random sample size
Authors: Voorn W. J.
Published: April 2006

Maximum stability of a distribution with respect to a positive integer random variable N is defined by the property that the type of distribution is not changed when considering the maximum value of N independent observations. The logistic distribution is proved to be the only symmetric distribution which is maximum stable with respect to each member of a sequence of positive integer random variables assuming value 1 with probability tending to 1. If a distribution is maximum stable with respect to such a sequence and minimum stable with respect to another, then it must be logistic, loglogistic or ‘backward' loglogistic. The only possible sample size distributions in these cases are geometric.
On the use of time series representations of population models
Authors: Heyde C. C.
Published: April 2006

Many population models which are far from stationarity can nevertheless be written in autoregressive format, perhaps with random coefficient. It is the thesis of this paper that procedures developed for stationary time series models are a useful guide to inferential results for population processes and may indeed be directly applicable. The illustrations concentrate on estimation of the matrix of mean vital rates in an age-structured population.
Data structures—the problem of time series computing
Authors: Henstridge John
Published: April 2006

The scope of statistical packages is largely defined by the data structures supported. It is claimed that none of the standard structures used in major packages is wholly suitable for time series data and this is the major reason why time series has not benefited from modern developments in statistical computing.
On a property of finite-state birth and death processes
Authors: Branford A. J.
Published: April 2006

A simple proof is given of the result that the ‘overflow' from a finite-state birth and death process is a renewal stream characterized by hyperexponential inter-event times. Our structure is utilized to give a converse result that any hyperexponential renewal stream can be so produced as the overflow from a finite-state birth and death process.
Note on generalizations of Mecke's formula and extensions of H = λG
Authors: Miyazawa Masakiyo
Published: April 2006

Mecke's formula is concerned with a stationary random measure and shift-invariant measure on a locally compact Abelian group , and relates integrations concerning them to each other. For , we generalize this to a pair of random measures which are jointly stationary. The resulting formula extends the so-called Swiss Army formula, which was recently obtained as a generalization for Little's formula. The generalized Mecke formula, which is called GMF, can be also viewed as a generalization of the stationary version of H = λG. Under the stationary and ergodic assumptions, we apply it to derive many sample path formulas which have been known as extensions of H = λG. This will make clear what kinds of probabilistic conditions are sufficient to get them. We also mention a further generalization of Mecke's formula.
Further studies of bivariate Bonferroni-type inequalities
Authors: Galambos Janos , Lee Min-Young
Published: April 2006

Let A1, A2, …, An and B1, B2,. ., BN be two sequences of events on the same probability space. Let mn(A) and mN(B), respectively, be the number of those Aj and Bj which occur. Let Si,j denote the joint ith binomial moment of mn(A) and jth binomial moment of mN(B), 0 ≤ i ≤ n, 0 ≤ j ≤ N. For fixed non-negative integers a and b, we establish both lower and upper bounds on the distribution P(mn(A) = r, mN(B) = u) by linear combinations of Si,j, 0 ≤ i ≤ a, 0 ≤ j ≤ b. When both a and b are even, all mentioned S¡,j are utilized in both the upper and the lower bound. In a set of remarks the results are analyzed and their relation to the existing literature, including the univariate case, is discussed.
A geometric invariant in weak lumpability of finite Markov chains
Authors: Ledoux James
Published: April 2006

We consider weak lumpability of finite homogeneous Markov chains, which is when a lumped Markov chain with respect to a partition of the initial state space is also a homogeneous Markov chain. We show that weak lumpability is equivalent to the existence of a direct sum of polyhedral cones that is positively invariant by the transition probability matrix of the original chain. It allows us, in a unified way, to derive new results on lumpability of reducible Markov chains and to obtain spectral properties associated with lumpability.
More on optimal allocation of components in coherent systems
Authors: Meng Fan C.
Published: April 2006

More applications of the principle for interchanging components due to Boland et al. (1989) in reliability theory are presented. In the context of active redundancy improvement we show that if two nodes are permutation equivalent then allocating a redundancy component to the weaker position always results in a larger increase in system reliability, which generalizes a previous result due to Boland et al. (1992). In the case of standby redundancy enhancement, we prove that a series (parallel) system is the only system for which standby redundancy at the component level is always more (less) effective than at the system level. Finally, the principle for interchanging components is extended from binary systems to the more complicated multistate systems.
Analysis of a two-queue model with Bernoulli schedules
Authors: Lee Duan-Shin
Published: April 2006

In this paper we analyze a single server two-queue model with Bernoulli schedules. This discipline is very flexible and contains the exhaustive and 1-limited disciplines as special cases. We formulate the queueing system as a Riemann boundary value problem with shift. The boundary value problem is solved by exploring a Fredholm integral equation around the unit circle. Some numerical examples are presented at the end of the paper.
Performance analysis of the discrete-time GI/Geom/1/N queue
Authors: Chaudhry M. L. , Gupta U. C.
Published: April 2006

This paper presents an analysis of the single-server discrete-time finite-buffer queue with general interarrival and geometric service time, GI/Geom/1/N. Using the supplementary variable technique, and considering the remaining interarrival time as a supplementary variable, two variations of this model, namely the late arrival system with delayed access (LAS-DA) and early arrival system (EAS), have been examined. For both cases, steady-state distributions for outside observers as well as at random and prearrival epochs have been obtained. The waiting time analysis has also been carried out. Results for the Geom/G/1/N queue with LAS-DA have been obtained from the GI/Geom/1/N queue with EAS. We also give various performance measures. An algorithm for computing state probabilities is given in an appendix.
Exact results for a secretary problem
Authors: Quine M. P. , Law J. S.
Published: April 2006

We consider the following secretary problem: items ranked from 1 to n are randomly selected without replacement, one at a time, and to ‘win' is to stop at an item whose overall rank is less than or equal to s, given only the relative ranks of the items drawn so far. Our method of analysis is based on the existence of an imbedded Markov chain and uses the technique of backwards induction. In principal the approach can be used to give exact results for any value of s; we do the working for s = 3. We give exact results for the optimal strategy, the probability of success and the distribution of T, and the total number of draws when the optimal strategy is implemented. We also give some asymptotic results for these quantities as n → ∞.
Genetic parameters for osteochondrosis traits in elbow joints of crossbred pigs and relationships with production traits
Authors: Jørgensen B. , Nielsen B.
Published: April 2006

A total of 9360 offspring of 12 purebred Duroc sires and 692 Landrace × Yorkshire sows were evaluated for six osteochondrosis traits in the left elbow joints at slaughter. Osteochondrosis traits, growth pre- and post weaning, and meat content at slaughter were analysed simultaneously by a multivariate genetic model. Castrates scored worse than female pigs for nearly all osteochondral traits. Heritability of elbow osteochondrosis was moderate (0·02 to 0·28) and, thus, selection against the disorder is possible. Phenotypic correlations among joint surface abnormalities, cartilage thickness, subchondral lesions and cracks in the cartilage at the osteochondral junction in the medial condyle ranged from 0·33 to 0·69, whereas genetic correlations ranged from 0·75 to 0·97. Phenotypic correlations of the sagittal central groove with other abnormalities in the medial condyle were low and insignificant but genetic correlations were strongly significant (0·66 to 0·77). Depression of the proximal edge of the radius was to some extent phenotypically correlated to abnormalities in the medial humeral condyle (around 0·2), while genetic correlations ranged from 0·05 to 0·52. Significant genetic correlations among osteochondral traits indicate that all are part of the osteochondrosis complex. Abnormalities in the joint surface showed the strongest genetic correlations with other osteochondrosis variables in the elbow joint and were moderately inherited (h2= 0·22), which indicates that this trait can be used as a marker to select against osteochondrosis. Osteochondral traits had no significant genetic correlations with growth to weaning and to 30 kg, slight negative (favourable) genetic correlations with growth from 30 to 100 kg, and slightly positive (unfavourable) genetic correlations with meat content in carcass.
Dietary manipulation post weaning to improve piglet performance and gastro-intestinal health
Authors: Pierce K.M. , Sweeney T. , Brophy P.O. , Callan J.J. , McCarthy P. , O'Doherty J.V.
Published: April 2006

Two experiments were conducted to investigate the use of dietary manipulation as a means of improving piglet post-weaning performance and gastro-intestinal health. In experiment 1, 144 piglets (24 days old) in a 3 × 2 factorial arrangement were offered diets containing 65, 170 and 280 g lactose per kg with or without lactic acid (16 g/kg) for 28 days. In experiment 2, 20 piglets (24 days old) (in a 2 × 2 factorial arrangement were offered the following diets for 7 days and then sacrificed: T1) basal diet; T2) basal diet + 15 g inulin per kg; T3) basal diet + 16 g lactic acid per kg and T4) basal diet + 15 g inulin per kg + 16 g lactic acid per kg. After slaughtering, tissue samples were taken from the duodenum, jejunum and ileum for morphological measurements. Digesta samples were taken from the ileum, caecum and colon for microbiology and volatile fatty acid analysis. In experiment 1, pigs offered diets containing lactic acid had improved daily gain (P< 0·01) and food efficiency (P< 0·05) from days 0 to 7 compared with pigs offered diets containing no lactic acid. There was a linear increase (P< 0·05) in average daily gain (ADG) from days 0 to 28 and a linear decrease in faecal pH (P< 0·01) with increasing lactose levels. There was a quadratic effect of lactose on food conversion ratio from days 0 to 28 (P< 0·05). In experiment 2, there was a significant interaction between inulin and lactic acid in villous height in the jejunum (P< 0·001) and the concentrations of lactobacilli (P< 0·1) andE. coli(P< 0·05) in the colon. The inclusion of inulin and lactic acid resulted in a significant increase in villous height compared with the inulin only diet (P< 0·001). However, lactic acid had no effect on villous height in pigs offered diets without inulin supplementation. The inclusion of lactic acid and inulin caused a significant increase in both lactobacilli andE. coliconcentrations compared with the inulin only diets (P< 0·05). However, neither inulin nor lactic acid had an effect on lactobacilli andE. colinumbers in isolation of the other. In conclusion, in experiment 1, lactic acid improved performance in the 1st week post weaning. There was a linear increase in ADG with increasing lactose levels. In experiment 2, the combination of lactic acid and inulin increased villous height in the jejunum and concentrations of lactobacilli andE. coliin the colon.
The effects of anAspergillus oryzaeextract containing alpha-amylase activity on ruminal fermentation and milk production in lactating Holstein cows
Authors: Tricarico J. M. , Johnston J. D. , Dawson K. A. , Hanson K. C. , McLeod K. R. , Harmon D. L.
Published: April 2006

The effects of anAspergillus oryzaeextract containing alpha-amylase activity (Amaize™, Alltech Inc., Nicholasville, KY) were examinedin vivoandin vitro. A lactating cow study employed 20 intact and four ruminally fistulated Holstein cows in a replicated 4 × 4 Latin-square design to examine the effects of four concentrations of dietary Amaize™ extract on milk production and composition, ruminal fermentation and serum metabolite concentrations. The treatment diets contained 0, 240, 480 or 720 alpha-amylase dextrinizing units (DU) per kg of total mixed ration (TMR) (dry-matter basis). The supplemental alpha-amylase increased the yields of milk (P= 0·02), fat (P= 0·02) and protein (P= 0·06) quadratically. The maximum milk yield was obtained when 240 DU per kg of TMR were offered. Ruminalin situstarch disappearance was not affected by alpha-amylase supplementation in lactating cows or ruminally cannulated steers. Supplemental alpha-amylase extract reduced the molar proportion of propionate in the rumen of steers (P= 0·08) and lactating cows (P= 0·04), and in rumen-simulating cultures (P= 0·04). The supplement also increased the molar proportions of acetate (P= 0·06) and butyrate (P= 0·05), and the serum beta-hydroxybutyrate (P= 0·01) and non-esterified fatty acid (P= 0·03) concentrations in lactating cows. The improvements in milk production appear to be a consequence of the effects of alpha-amylase on ruminal fermentation and the potential changes in nutrient metabolism that result from them. We conclude that supplemental alpha-amylase may be given to modify ruminal fermentation and improve milk and component yield in lactating Holstein cattle.
Short‐term impact of disturbance on genetic diversity and structure of Indonesian populations of the butterfly Drupadia theda in East Kalimantan
Authors: FAUVELOT C. , CLEARY D. F. R. , MENKEN S. B. J.
Published: April 2006

We investigated the short‐term impact of disturbance on genetic diversity and structure of the tropical butterfly Drupadia theda Felder (Lepidoptera: Lycaenidae). Populations were sampled from five landscapes in East Kalimantan (Borneo, Indonesia) which were differentially disturbed by selective logging and the 1997/1998 El Niño Southern Oscillation (ENSO)‐induced drought and fires. Sampling occurred before (in 1997) and after the forest fires (in 1998, 1999, 2000, and 2004). Drupadia theda populations underwent serious population size reductions following the 1997/1998 ENSO event. For a total of 208 individuals, we sequenced a 509‐bp segment of mtDNA containing the control region plus the 5’ end of the 12S rDNA gene. Haplotype diversity in D. theda populations ranged from 0.468 to 0.953. Just after the 1997/1998 ENSO event, number of recorded individuals and genetic diversity were very low in D. theda populations sampled in the two severely burned areas and in a small pristine forest fragment that was surrounded by burned forest and thereby affected by drought. Interestingly, higher levels of genetic diversity were observed in logged forest compared to proximate pristine forest. After 1998, the genetic composition within the three ENSO‐disturbed areas diverged. In the twice‐burned forest, the genetic diversity in 1999 already approached pre‐fire levels, while it remained nearly unchanged in proximate once‐burned forest. Our data suggest that the 1997/1998 ENSO‐induced drought and fires caused massive reductions in the genetic diversity of D. theda and that population recoveries were linked to their geographical position relative to patches of unburned forest (and thus to source populations).
Membrane‐associated transcripts in Arabidopsis; their isolation and characterization by DNA microarray analysis and bioinformatics
Authors: De Jong Mark , Van Breukelen Bas , Wittink Floyd R. , Menke Frank L.H. , Weisbeek Peter J. , Ackerveken Guido Van den
Published: April 2006

Membrane‐associated, integral membrane and secreted proteins are of key importance in many cellular processes. For most of the 28 952 predicted proteins in Arabidopsis, the actual subcellular localization has not been demonstrated experimentally. So far, their potential membrane‐association has been deduced from algorithms that predict transmembrane domains and signal peptides. However, the comprehensiveness and accuracy of these algorithms is still limited. The majority of membrane‐associated and secreted proteins is synthesized on membrane‐bound polysomes. Therefore, the isolation and characterization of mRNA associated with membrane‐bound polysomes offers an experimental tool for the genome‐wide identification of these proteins. Here we describe an efficient method to isolate mRNA from membrane‐bound polysomes and report on the validation of the method to enrich for transcripts encoding membrane‐associated and secreted proteins. The sensitivity and reproducibility of the isolation method was investigated by DNA microarray analysis. Pearson correlations between transcript levels obtained from three replicate isolations showed that the method is highly reproducible. A significant enrichment for mRNAs encoding proteins containing predicted transmembrane domains and signal peptides was observed in the membrane‐bound polysomal fraction. In this fraction, 301 transcripts were classified by gene ontologies as ‘cellular component unknown’, and potentially encode previously unrecognized secreted or membrane‐associated proteins.
The relationship between serum endothelin (ET)‐1 and wheezing status in the children with Mycoplasma pneumoniae pneumonia
Authors: Chung Hai Lee , Kim Sang Gyung , Shin Im Hee
Published: April 2006

Although Mycoplasma pneumoniae infection is known to be associated with acute wheezing and the exacerbation of asthma, the mechanism by which this pathogen contributes to the development of wheeze‐related symptoms is not fully understood. The aim of our study was to examine serum endothelin (ET)‐1 and other cytokines in acute M. pneumoniae pneumonia and investigate if there is any relation between these inflammatory mediators and the occurrence of wheezing. We studied 53 patients, aged 3–13 yr, who admitted with pneumonia. These patients were divided into three groups: M. pneumoniae pneumonia with wheeze (n = 23) and without wheeze (n = 19), and the patients without the evidence of M. pneumoniae infection (n = 11). Age‐matched controls (n = 10) were also studied. The serum concentrations of ET‐1, interleukin (IL)‐5 and IL‐18 were measured using ELISA kits in patient groups and controls. The patients with M. pneumoniae pneumonia had significantly higher serum ET‐1 than those without evidence of M. pneumoniae infection. In the presence of M. pneumoniae pneumonia, ET‐1 concentrations were significantly higher in the patients with wheeze than those without wheeze. IL‐5 and IL‐18 in each patient group were higher compared to controls. However, no significant between‐group difference was observed. Total serum IgE levels were significantly higher in the patients with M. pneumoniae pneumonia and wheeze than in those without wheeze. A positive correlation was observed between serum ET‐1 and total IgE in the patients with M. pneumoniae pneumonia and wheeze. Our results may suggest a role of ET‐1 in the occurrence of acute wheezing or exacerbation of asthma associated with M. pneumoniae pneumonia.
Anesthetic management of preschool children with penetrating eye injuries: postal survey of pediatric anesthetists and review of the available evidence
Authors: SEIDEL JOCHEN , Dorman TERESA
Published: April 2006

Background : Pediatric anesthetists were surveyed regarding their anesthesia management of a screaming child with a penetrating eye injury. The results are reviewed in relation to the available evidence in the literature.

Methods : A postal survey was sent to all the members of the APA living in the UK. Seven clinical questions were asked regarding the management of penetrating eye injury and two questions regarding seniority and the number of cases seen.

Results : Of the 318 questionnaires sent out 238 were evaluated. Of the responders indicating the number of cases seen, 21.2% had never seen a single case, 55.1% had seen <5, 17.8% had seen 5–10, and 5.9% had seen >10 cases. Suxamethonium was used more often by respondents who had handled more cases; 42.9% of those doing >10 compared with 10% of those doing less than five cases. Senior anesthetists preferred the use of techniques without relaxants and to extubate children under deep anesthesia.

Conclusions : Few people have extensive experience managing a penetrating eye injury in a child. A variety of anesthesia techniques are used for induction with anesthetists avoiding suxamethonium, despite there being little evidence in the literature that the use of suxamethonium is harmful to the open globe.
The effects of caudal local anesthesia blockade on the Bispectral Index during general anesthesia in children
Authors: DAVIDSON ANDREW J. , IRONFIELD CRAIG M. , SKINNER ADAM V. , FRAWLEY GEOFF P.
Published: April 2006

Background:  Peripheral deafferentation induced by epidural or spinal anesthesia reduces the degree of cortical arousal in adults. This study aimed at determining if caudal blockade decreases the level of arousal, as measured by Bispectral Index (BIS) in unstimulated children, and to determine if this effect differed between age groups.

Methods:  Hospital ethics committee approval and parental consent was obtained. Children (age between 24 months and 5 years) and infants (between 6 and 24 months of age) were recruited if they were scheduled for below umbilical surgery that would usually require caudal local anesthesia blockade. Before the procedure, subjects within each age group were randomized to either caudal group (1 ml·kg−1 0.25% bupivacaine), or control group (no caudal). In all groups, anesthesia was induced with sevoflurane and maintained at a constant endtidal concentration of 1.5% sevoflurane without N2O. Five minutes after induction a baseline BIS was recorded (BIS1). In the caudal groups, a caudal block was then performed while in the control groups no block was performed. Fifteen minutes later, the BIS was again recorded (BIS2). The change in BIS over this time period was the primary outcome (BISΔ). After measurement, subjects in the control groups received a caudal block before the start of surgery.

Results:  Twenty‐nine infants and 18 children completed the study protocol. In children, BISΔ was significantly different between the caudal group and control (−5.7 vs −0.7, P = 0.04). In infants, no significant difference was detected in BISΔ between caudal and control groups.

Conclusions:  Caudal blockade decreased the degree of arousal, as measured by BIS, in unstimulated children aged 2–5 years. No change in arousal was detected in infants.
Repeat episodes of severe muscle rigidity in a child receiving sevoflurane
Authors: COHEN IRA TODD , KAPLAN RICHARD
Published: April 2006

We report on a patient who developed two episodes of severe muscle rigidity, increased endtidal CO2 and increased creatine phosphate kinase associated with sevoflurane anesthesia. Dysrhythmias and hyperthermia were not observed and dantrolene was not administered. Genetic testing for the 17 known mutations associated with malignant hyperthermia (MH) was negative. Although we cannot rule out MH or other neuromuscular diseases we suggest that this rare event may be a direct effect of sevoflurane.
Diversity of Synechococcus and Prochlorococcus populations determined from DNA sequences of the N‐regulatory gene ntcA
Authors: Penno Sigrid , Lindell Debbie , Post Anton F.
Published: April 2006

The cyanobacteria Synechococcus and Prochlorococcus are abundant primary producers in the nitrogen‐poor waters of the Gulf of Aqaba, northern Red Sea. Expression of the nitrogen regulatory gene ntcA is a useful indicator for determining the N‐status of cyanobacteria, and preliminary work with this gene suggests that it may also serve as a useful biodiversity marker. Here we investigated the genotypic diversity of ntcA among the full spectrum of cultured Synechococcus and Prochlorococcus lineages and assessed cyanobacterial genotypic composition in environmental samples from the Gulf of Aqaba. The high level of ntcA diversification established this gene as an excellent biodiversity marker capable of distinguishing between numerous clades within each genus with high resolution. An unexpected large diversity was observed among Synechococcus populations, including the detection of four novel clades for which culture representatives have yet to be isolated. In addition, extensive microdiversity within a number of Synechococcus clades was revealed. Temporal differences in the detection of the various Synechococcus clades suggest seasonal fluctuations in the genotypic make‐up of Synechococcus populations. In contrast, virtually all Prochlorococcus sequences fell within a single high‐light adapted clade that was detected year round. We suggest that the limited genotypic diversity among Prochlorococcus in combination with a limited capacity for acclimation to environmental changes resulting from its small genome size led to the dramatic rise and demise of Prochlorococcus populations over the yearly cycle in the Gulf of Aqaba.
Efficient Frequency Estimation from a Particular Almost Periodic Function with Application to Laser Vibrometry
Authors: Lévy‐Leduc Céline
Published: April 2006

Abstract.  We considered the problem of estimating the frequency of an unknown periodic function from observations which consist of a particular almost periodic function and additive Gaussian white noise from both theoretical and practical points of view. First, we proved that, in a precise asymptotic framework, our estimator was consistent and asymptotically efficient. Then, when the number of observations was fixed, we proposed a practical implementation of the procedure and compared its performance with those forecast by the theoretical study. Finally, we applied our processing to some laser vibrometry signals and compared it with a technique classically used in this field.