bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exact sampling distributions from the infinite neutral alleles model
Authors: Griffiths R. C. 
Published: April 2006

The exact transient sampling distribution is found for the infinite neutral alleles model with mutation, thus extending the stationary distribution found by Ewens (1972). The first eigenfunction in the sampling distribution depends only on the homozygosity. In a large sample the expected number of allele types is close to the expected number in a stationary distribution and depends little on the initial frequencies or the time of sampling. The expected number of types in a sample for a non-stationary population is tabulated.The sampling distribution from a population with no mutation is found. The probability that the population is monomorphic given that the sample contains only one type is tabulated, where initially the population has a large number of alleles with equal frequencies.A study is made of the joint distribution of the allele frequencies in two samples taken timetapart from a stationary population. Of particular interest is the number of allele types in common in two such samples. The distribution of the number of types in common in a population viewed at timetapart is also found and tabulated for different mutation rates and time. The expected frequency of the allele types in common is tabulated.The distribution of allele frequencies in two divergent populations of common ancestry is shown to be the same as the distribution of frequencies in a single population at two time points 2tapart. A sufficient statistic for the time of divergence is shown to be the paired frequencies of the allele types in common. The expected waiting time until the populations have no allele types in common is tabulated.
Comments on the age distribution of Markov processes
Authors: Pakes Anthony G. , Tavaré Simon 
Published: April 2006

Previous work on the concept of a limiting conditional age distribution of a discrete-state continuous-time Markov process with one absorbing state is generalised. The generalisation allows this process to have a finite number of absorbing states and the associated return process to have an arbitrary initial distribution on the transient states of the absorbing process. If the return process is ρ-recurrent, possesses the strong ratio limit property and satisfies some further requirements then the limiting age distribution exists. The proof of this result requires a new representation of the ρ-invariant measure of the return process.The following examples are treated, (a) finite state space birth-death processes, (b) Markov branching processes and the linear death process, and (c) the linear birth and death process with killing.
An infinite-alleles version of the simple branching process
Authors: Griffiths R. C. , Pakes Anthony G. 
Published: April 2006

Individuals in a population which grows according to the rules defining the simple branching process can mutate to novel allelic forms. We obtain limit theorems for the number of alleles present in any generation, the total number of alleles ever seen and the number of the generation containing the last mutation event.In addition we define a notion of frequency spectrum for each generation as the expected number of alleles having a given number of representatives. As the generation number increases we prove the existence of a limiting notion of the frequency spectrum and discuss its upper tail behaviour. Our results here are incomplete and we make some conjectures which are supported by informal argument and specific examples.
Semi-Markov shock models with additive damage
Authors: Posner M. J. M. , Zuckerman D. 
Published: April 2006

We examine a replacement model for a semi-Markov shock model with additive damage. Sufficient conditions are given for the optimality of control limit policies. The paper generalizes and unifies previous research in the area.In addition, we investigate in detail the practical modelling and computational aspects of the replacement problem using a semi-Markov modelling structure.
Asymptotic expansions of moments of the waiting time in closed and open processor-sharing systems with multiple job classes
Authors: Mitra Debasis , Morrison J. A. 
Published: April 2006

We present new results based on novel techniques for the problem of characterizing the waiting-time distribution in a class of queueing networks. We give effective methods for computing, for each of possibly several job-classes, the second moment of the equilibrium waiting time for closed systems as well as for open systems. Both open and closed systems have a CPU operating under the processor-sharing (‘time-slicing') discipline in which service-time requirements may depend on job-class. The closed system also includes a bank of terminals grouped according to job-classes, with the class structure allowing distinctions in the user's behavior in the terminal. In the contrasting open system, the job streams submitted to the CPU are Poisson with rate parameters dependent on job-classes.Our results are exact for the open system and, for the closed system, in the form of an asymptotic series in inverse powers of a parameter N. In fact, the result for open networks is simply the first term in the asymptotic series. For larger closed systems, the parameter N is larger and thus fewer terms of the series need be computed to achieve a desired degree of accuracy. The complexity of the calculations for the asymptotic expansions is polynomial in number of classes and, importantly, independent of the class populations. Only the results on the single-class systems, closed and open, were previously known.
The cyclic queue with one general and one exponential server
Authors: Boxma O. J. 
Published: April 2006

This paper considers the two-stage cyclic queueing model consisting of one general (G) and one exponential (M) server. The strong connection between the present model and the M/G/1 model (with finite waiting room) is exploited to yield the joint distribution of the successive response times of a customer at the G queue and the M queue. This result reveals a surprising phenomenon: in general there is a difference between the joint distribution of the two successive response times at (first) the G queue and (then) the M queue, and the joint distribution of the two successive response times at (first) the M queue and (then) the G queue.Another associated result is an expression for the cycle-time distribution. Special consideration is given to the case that the number of customers in the system tends to ∞, while the mean service times tend to 0 at an inversely proportional rate.
ESS modelling of diploid populations II: stability analysis of possible equilibria
Authors: Hines W. G. S. 
Published: April 2006

In order to determine the robustness of the mean-covariance approach to exploring behavioural models of sexual diploid biological populations which are based on the evolutionarily stable strategy (ESS) concept, a companion paper explored relevant features of the probability simplex of allelic frequencies for a population which is genetically homogeneous except possibly at a single locus.The Shahshahani metric is modified in this paper to produce a measure of distance near an arbitrary frequency F in the allelic simplex which can be used when some alleles are given zero weight by F. The equation of evolution for the modified metric can then be used to show that certain sets of frequencies (corresponding to equilibrium mean strategies) act as local attractors, as long as the mean strategies corresponding to those sets are non-singular or even, in most cases, singular. We identify conditions under which the measure of distance from an initial frequency to a nearby set of equilibrium frequencies corresponding to exceptional mean strategies might increase, either temporarily or for a protracted length of time.
The Minimum Vertex Degree of a Graph on Uniform Points in [0, 1]d
Authors: Appel Martin J. B. , Russo Ralph P. 
Published: April 2006

This article continues an investigation begun in [2]. A random graph Gn(x) is constructed on independent random points U1, · ··, Un distributed uniformly on [0, 1]d, d ≧ 1, in which two distinct such points are joined by an edge if the l∞-distance between them is at most some prescribed value 0 < x < 1.Almost-sure asymptotic results are obtained for the convergence/divergence of the minimum vertex degree of the random graph, as the number n of points becomes large and the edge distance x is allowed to vary with n. The largest nearest neighbor link dn, the smallest x such that Gn(x) has no vertices of degree zero, is shown to satisfy

Series and sequence criteria on edge distances {xn} are provided which guarantee the random graph to be complete, a.s. These criteria imply a.s. limiting behavior of the diameter of the vertex set.
Comparison of differentiation estimates based on morphometric and molecular data, exemplified by various leaf shape descriptors and RAPDs in the genus Chaenomeles (Rosaceae)
Authors: Rumpunen Kimmo , Bartish Igor V. 
Published: April 2006

AbstractThe efficiency of classical metric descriptors (MDs), normalised elliptic Fourier coefficients (EFCs), and the power series of normalised elliptic Fourier coefficients (PEFCs) in revealing variation in leaf shape was evaluated and compared for species in the genus Chaenomeles, using canonical variates analyses (CVAs) and reclassification tests. For EFCs 30 harmonics (and for PEFCs 40 harmonics) were needed to achieve 100% correct reassignment of plants. By contrast, MDs were considerably less efficient and only 87%, 77% and 66% of the plants were correctly reassigned to species, populations, and maternal families, respectively. Furthermore, when compared with data based on molecular random amplified polymorphic DNA markers (RAPDs), PEFCs produced the most concordant data sets as revealed by cluster analyses. To obtain comparable estimates of variability and differentiation, the AMOVA approach was used both for molecular data and, as a novelty, for quantitative morphometric data. The variation was partitioned by hierarchical extraction of variance components from matrices of standardised squared Euclidean distances, and differentiation estimates were obtained as Φ­statistics. All descriptor sets partitioned the variance in a similar way. Surprisingly high correlations were found between RAPDs and elliptic Fourier transforms for the among­family estimates of variance components (RAPDs vs. PEFCs: 0.89, P = 0.003; RAPDs vs. EFCs: 0.86, P = 0.006). In contrast, only a moderate correlation was found between RAPDs and MDs (0.71, P = 0.049). This may indicate that shape per se (the size component excluded) is a less biased estimator of genetic variation than metric leaf descriptors in the genus Chaenomeles. Estimates of population differentiation based on EFCs and PEFCs were always lower than differentiation estimates based on RAPDs, whereas the differentiation estimates based on MDs were in general higher than estimates based on RAPDs, except for one species including hybrid populations.
Phylogeny of Isoëtes (Lycopsida): resolving basal relationships using rbcL sequences
Authors: Rydin Catarina , Wikström Niklas 
Published: April 2006

AbstractThe phylogenetic relationships of Isoëtes (Isoëtaceae) were investigated by means of a cladistic analysis using plastid rbcL sequences and a representative sample of 18 species. The analysis supports a basal split in Isoëtes separating two main groups, one including aquatic species from South America (I. bradei and I. amazonica) and West Africa (I. kersii and I. schweinfurthii), and the other including aquatic, amphibious and terrestrial species representing all major continents. Higher level relationships remain unresolved, but supported groups do conflict with previous morphology­based hypotheses. Comparatively low levels of sequence divergence indicate that the use of more rapidly evolving regions will be required to resolve higher level relationships. The phylogenetically isolated nature of Isoëtes will in such analyses make standard outgroup comparisons problematic, and results presented here will in this respect prove important by providing support for choosing among alternative rooting options.
Four succulent families and 40 million years of evolution and adaptation to xeric environments: What can stem and leaf anatomical characters tell us about their phylogeny?
Authors: Landrum James V. 
Published: April 2006

AbstractFour families of the eleven or so families of Caryophyllales have been particularly successful at adapting to xeric environments: (1) ice plants (Aizoaceae), (2) cacti (Cactaceae), (3) "Old World cacti" (Didiereaceae); and (4) portulacs (Portulacaceae). Ice plants adapted to the harsh conditions of the deserts of southern Africa; many evolved leaf succulence to an extreme degree, some went underground, others lost the ability to make normal wood, and all had to adapt their reproductive strategies in pollination or seed dispersal. Cacti adapted to deserts of South, Central, and North America by losing their leaves over time and evolving various types of succulent stems. Cacti also adapted by greatly reducing the presence of vessels in their wood, evolving a novel tracheid type termed wide­band tracheids, and evolving CAM and C4 metabolisms. Plants of Didiereaceae adapted to the harsh Madagascan environment by evolving both stem and leaf succulence and the columnar stem form, but these plants maintained their normal, non­anomalous woody growth. Members of Portulacaceae evolved in many different xeric areas of southern Africa, but all evolved leaf succulence and limited stem succulence, much the same as found in Aizoaceae. Each family evolved varying strategies for living in water­stressed environments. Common themes among these distantly related plants are leaf and/or stem succulence, and anatomical and physiological adaptations.
Lines, outlines, and landmarks: morphometric analyses of leaves of Acer rubrum, Acer saccharinum (Aceraceae) and their hybrid
Authors: Jensen Richard J. , Ciofani Kristen M. , Miramontes Lydia C. 
Published: April 2006

AbstractQuantitative comparisons of leaf morphology for evaluating taxonomic relationships may be conducted by traditional morphometrics, outline analyses, or geometric morphometrics. These approaches were employed for examining relationships among trees of two species of maple, Acer rubrum and A. saccharinum, and their hybrid (A. ×freemanii). Leaf samples from six hybrid trees (three each from two accessions) and 40 trees field identified as either species were pressed and dried. Leaf outline and landmark data were captured for each leaf, and linear and angular measures were derived from the landmark configurations. A vector of character means, a mean leaf outline, and a consensus landmark configuration were generated for each tree. Traditional morphological measurements, a single­parameter outline descriptor, elliptic Fourier coefficients of the outlines, and relative warp scores for the landmarks were used to depict relationships among the 46 OTUs. All three data types reveal similar patterns with respect to the two species, and the hybrids are generally intermediate between the two species. The results provide evidence of genetic segregation in one hybrid accession, that several of the field sampled trees are naturally occurring hybrids, and that relative warps analysis can reveal aspects of shape variation not detected by the other analyses.
Ehrenfest urn models
Authors: Karlin Samuel , McGregor James 
Published: April 2006

In the Ehrenfest model with continuous time one considers two urns and N balls distributed in the urns. The system is said to be in state i if there are i balls in urn I, N − i balls in urn II. Events occur at random times and the time intervals T between successive events are independent random variables all with the same negative exponential distributionWhen an event occurs a ball is chosen at random (each of the N balls has probability 1/N to be chosen), removed from its urn, and then placed in urn I with probability p, in urn II with probability q = 1 − p, (0 < p < 1).
The general N server finite queue
Authors: Kapadia Asha Seth 
Published: April 2006

Kingman (1962) studied the effect of queue discipline on the mean and variance of the waiting time. He made no assumptions regarding the stochastic nature of the input and the service distributions, except that the input and service processes are independent of each other. When the following two conditions hold:
(a)no server sits idle while there are customers waiting to be served;(b)the busy period is finite with probability one (i.e., the queue empties infinitely often with probability one);
he has shown that the mean waiting time is independent of the queue discipline and the variance of the waiting time is a minimum when the customers are served in order of their arrival. Conditions (a) and (b) will henceforward be called Kingman conditions and a queueing system satisfying Kingman conditions will be referred to in the text as a Kingman queue.
Exact and limiting distribution of sustained maxima
Authors: Canfield E. R. , McCormick W. P. 
Published: April 2006

Define a random variable
We refer to Yn as a sustained maximum. Under the assumption that the Xi's are i.i.d. the exact distribution of Yn is obtained. Under certain conditions on the underlying distribution F we obtain weak limit results for the Yn as well. Also a combinatorial extreme-value problem is solved.
Adrenal responsiveness of reindeer (Rangifer tarandus tarandus) to intravenously administered ACTH
Authors: Säkkinen H. , Tornberg J. , Goddard P. J. , Eloranta E. , Dahl E. , Ropstad E. , Saarela S. 
Published: April 2006

AbstractPlasma cortisol concentrations were determined from the blood of eight mature female reindeer (Rangifer tarandus tarandus) after an intravenous injection of either saline (control) or 100, 250 or 500 μg of synthetic ACTH. Blood samples were collected at 0, 2, 4, 6, 8, 10, 15, 20, 25, 30, 45, 60, 75, 90, 120, 150, and 180 min after the injections. The aims were to determine the appropriate dose of ACTH for adrenal stimulation tests, to define the dose level of ACTH which elicited a maximal cortisol response and to describe the range of blood cortisol concentrations for reference when evaluating the stress responses of reindeer.The mean plasma cortisol concentrations (s.e.) at the zero sample times (t0) of the control and the ACTH treatments varied between 93·4 (11·8) and 132·5 (18·1) nmol/l. The total plasma cortisol response (area under curve, AUC, nmol/l × min) increased with increasing dose of ACTH (P < 0·001). The AUC of the control treatment was significantly smaller than of the ACTH treatments (P < 0·001). The highest dose of ACTH (500 μg) gave a significantly bigger AUC than the lowest dose (100 μg) (P = 0·008). The maximal plasma cortisol concentrations (CMAX) were achieved within 60 min of the ACTH injections. The ranges of individual CMAX were 59·0 to 136·8 nmol/l for the control treatment, and 110·0 to 252·0, 152·0 to 247·5 and 135·1 to 257·1 nmol/l for 100, 250 and 500 μg ACTH, respectively. The difference in CMAX was significant between the control treatment and the ACTH treatments (P < 0·001) but not between the different doses of ACTH. The plasma cortisol concentrations at the end of the observation period at t180 were not significantly affected by the ACTH treatment (P > 0·05).In conclusion, the 100-μg dose of ACTH was sufficient to produce a significant cortisol response compared with the control treatment. Increasing the dose did not increase the maximal response, but tended to elongate the response profile. The blood sampling frequency used in the study was found suitable for detection of the cortisol response in reindeer.
Effect of herbage allowance and concentrate food level offered to ewes in late pregnancy on ewe and lamb performance
Authors: Dawson L. E. R. , Carson A. F. , Kilpatrick D. J. , Laidlaw A. S. 
Published: April 2006

AbstractTwo experiments were undertaken to investigate the effect of herbage allowance and concentrate food level offered to twin-bearing ewes in the last 6 weeks of pregnancy on ewe and lamb performance. In each study, 96 twin-bearing Greyface (Border Leicester × Scottish Blackface), Rouge × Greyface and Texel × Greyface ewes were used. In experiment 1, the ewes were allocated to eight treatments consisting of two herbage allowances (1·3 and 2·6 kg herbage dry matter per ewe per day) and four concentrate food levels ranging from zero to 1000 g per day. In experiment 2, ewes were offered four herbage allowances (1·3, 1·75, 2·2 and 2·6 kg herbage dry matter per ewe per day) and zero or 500 g concentrates per day. In experiment 1, herbage allowance and concentrate food level had no significant effect on lamb birth weight, lamb mortality or lamb performance up to weaning. Herbage dry matter intake decreased linearly with increasing concentrate food level with a substitution rate of 18 g of herbage dry matter per 100 g concentrate food level. In experiment 2, lamb birth weight increased with increasing herbage allowance (P< 0·01) and with increasing concentrate food level (P< 0·01). However, lamb performance to weaning was unaffected by late pregnancy nutrition. The satisfactory levels of performance obtained with ewes offered grass-only diets in late pregnancy indicates that grazed grass is a high nutritive value food for twin-bearing ewes in late pregnancy.
Assessing cubicle dimensions for finishing bulls based on animal behaviour and cleanliness
Authors: Gygax L. , Westerath H. Schulze , Kuhlicke J. , Wechsler B. , Mayer C. 
Published: April 2006

AbstractFinishing bulls need increasingly large cubicles throughout their growth, and optimal cubicle dimensions may differ from those used for dairy cows. The space requirements of finishing bulls was investigated by observing standing-up and lying-down behaviour, lying duration and number of lying bouts, as well as the cleanliness of cubicles and animals before and after increasing cubicle size at four different points in time. Lying area in the cubicles measured 120 × 70 cm at the start and 185 × 110 cm at the end of the finishing period (approx. at 160 and 550 kg, respectively). Twenty animals kept in four groups were observed at weights of approximately 220, 330, 380 and 500 kg before and after cubicle dimensions were increased. The proportion of standing-up events with more than one head lunge decreased with enlargement of the cubicles (P = 0·01). As cubicle size increased, bulls hit the partition rails less on standing up, except at 220 kg weight where the pattern was inverted (interaction: P = 0·001). Partitions were also hit less on lying down as cubicle size increased, except at 220 kg weight with an inverse pattern (interaction: P = 0·01). The number of exploratory head sweeps before lying down did not change with cubicle enlargement (P > 0·5). Bulls slipped more often with cubicle enlargement, except at 380 kg where the difference was inverted (interaction: P = 0·03). They never fell and never turned around in the cubicles. In general, both animals and cubicles were very clean. On average, lying duration decreased (P < 0·01) while the number of lying bouts tended to increase (P = 0·052) with enlargement of the cubicles but the absolute differences were small. Consequently at each point in time, the smaller cubicles still seemed to provide sufficient lying space for the bulls. If the impacts with the partitions were minor and did not represent a serious welfare concern, as suggested by qualitative observations, the cubicle dimensions used could be considered suitable for housing the type of finishing bulls used in this study.