bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vestured pits: their occurrence and systematic importance in eudicots
Authors: Jansen Steven , Baas Pieter , Smets Erik 
Published: April 2006

SummaryJansen, S., Baas, P. & Smets, E.: Vestured pits: their occurrence and systematic importance in eudicots. – Taxon 50: 135–167. 2001. – ISSN 0040–0262.The distribution of vestured pits in secondary xylem reveals interesting patterns that may bear on hypotheses of phylogenetic relationships within eudicots. Vestured pits are found to be relatively widespread at the base of the eurosids I, eurosids II, and euasterids I, but the feature probably has been lost or originated independently in several more derived branches of these clades. Vestured pits characterise ordersMyrtalesandGentianalessensu APG; other large monophyletic taxa that consistently show vestured pits includeMalpighiaceae, Polygonaceae, Brassicaceae,and mostFabaceae.Representatives from euasterids II always show nonvestured pits. The occurrence of the character implies numerous parallel origins in the following divergent, major taxa: (1)Proteaceae,(2)Polygonaceae(Caryophyllales), (3) eurosids I (Zygophyllaceae, Fabales,very fewRosales, Malpighiales), (4) eurosids II (Myrtales, Malvales, Brassicales), and (5) euasterids I (Gentianales, Lamiales, Solanales). It is demonstrated that vestured pits frequently support results from DNA data.
New hypotheses of phylogenetic relationships in Barnadesioideae (Asteraceae) based on morphology
Authors: Urtubey Estrella , Stuessy Tod F. 
Published: April 2006

SummaryUrtubey, E. & Stuessy, T. F.: New hypotheses of phylogenetic relationships in Barnadesioideae (Asteraceae) based on morphology. ‐ Taxon 50: 1043–1066. 2001. — ISSN 0040–0262.Previous molecular sequence and restriction site data have confirmed subfamily Barnadesioideae as basal within Asteraceae. The subfamily consists of 88 species in nine genera: Arnaldoa, Barnadesia, Chuquiraga, Dasyphyllum, Doniophyton, Duseniella, Fulcaldea, Huarpea, and Schlechtendalia. Two morphological cladistic analyses among genera or subgeneric groups within this subfamily have been completed previously, with contrasting results. Because of the importance of understanding relationships in this group of early Asteraceae, especially for insights on character evolution within the family, comprehensive morphological cladistic analyses were conducted at the specific level. Initial investigations utilising 31 characters with all 88 species led eventually to curtailed studies with 52 species. Five different outgroup hypotheses were employed: Acicarpha laxa, A. spathulata, Calycera leucanthema, C. spinulosa (all Calyceraceae), and Schlechtendalia luzulaefolia (Barnadesioideae; as functional outgroup). The results confirm Schlechtendalia as basal within Barnadesioideae. Monophyly is also confirmed for all genera, sections Chuquiraga and Acanthophyllae of Chuquiraga, and subgenus Archidasyphyllum of Dasyphyllum. All cladograms show two major groups (although statistical support values are low): (1) Chuquiraga, Doniophyton and Duseniella; and (2) Arnaldoa, Dasyphyllum, Fulcaldea, Huarpea and Barnadesia. Although bilabiate (4+1) corollas occur in Schlechtendalia, tubular corollas are believed plesiomorphic for the subfamily because they are pervasive in Calyceraceae as well as in all other basal Barnadesioideae. Pollen with no shallow depressions also are hypothesised as plesiomorphic for Barnadesioideae, even though one depression occurs in Schlechtendalia. A southern South American origin of Barnadesioideae (and the entire family) is re‐emphasised. The previously hypothesised ancient lineage of Dasyphyllum subg. Archidasyphyllum, consisting of large trees, appears more derived in the new analyses.
Entodon challengeri (Paris) Cardot, the correct name for E. compress us sensu Mizushima and Cru m and Anderson
Authors: Iwatsuki Zennoske , Tan Benito C. 
Published: April 2006

SummaryIwatsuki, Z. & Tan, B. C: Entodon challengeri (Paris) Cardot, the correct name for E. compressus sensu Mizushima and Crum and Anderson. ‐ Taxon 50: 1125–1128. 2001. – ISSN 0040–0262.Entodon challengeri (Paris) Cardot is demonstrated to be the correct name for the taxon called E. compressus Müll. Hal. by Mizushima and by Crum and Anderson in their revisions and floristic account, respectively. Although validly published, Entodon compressus Müll. Hal. ex Cardot (1899) is shown to be an illegitimate later homonym of E. compressus (Hedw.) Müll. Hal. (1845), itself a synonym of Entodon cladorrhizans (Hedw.) Müll. Hal. (1845).
Lisianthius perkinsiae, a new name for Lisianthius acuminatus Perkins (Gentianaceae: Potalieae)
Authors: Struwe Lena , Weaver Richard E. 
Published: April 2006

SummaryStruwe, L. & Weaver, R. E.; Lisianthius perkinsiae, a new name for Lisianthius acuminatus Perkins (Gentianaceae: Potalieae). – Taxon 50: 1161–1162. 2001. ‐ ISSN 0040–0262.Lisianthius acuminatus Perkins from Veracruz, Mexico is a later homonym of Lisianthius acuminatus Desr., which is a synonym of Wurdackanthus frigidus (Sw.) Maguire & B. M. Boom from the Lesser Antilles. Therefore, Lisianthius acuminatus Perkins is here renamed Lisianthius perkinsiae Struwe & Weaver, nom. nov.
Name changes inPodostemaceae
Authors: Cook Christopher D. K. , Rutishauser Rolf 
Published: April 2006

SummaryCook, C. D. K. & Rutishauser, R.: Name changes inPodostemaceae. –Taxon 50: 1163–1167. 2001.‐ISSN 0040–0262.While preparing a review of the familyPodostemaceae, we have found it necessary to change the name of some species. Following rules of priority,CreniasK. P. J. Sprengel replacesMniopsisMartius. No convincing reasons can be found to maintain the monotypic generaHydrobryopsis, Malaccotristicha, SynstylisandTorrenticola; they are merged in their sister generaZeylanidium, Tristicha, HydrobryumandCladopus, respectively. On morphological groundsPolypleurella micrantherais transferred toHydrobryumandPolypleurum submersais transferred toSaxicolella.
The Species Plantarum Project, an international collaborative initiative for higher plant taxonomy
Authors: Brummitt Richard K. , Castroviejo Santiago , Chikuni Augustine C. , Orchard Anthony E. , Smith Gideon F. , Wagner Warren L. 
Published: April 2006

SummaryBrummitt, R. K., Castroviejo, S., Chikuni, A. C., Orchard A. E., Smith, G. F. & Wagner, W. L.: The Species Plantarum Project, an international collaborative initiative for higher plant taxonomy. – Taxon 50: 1217–1230. 2001. – ISSN 0040–0262.Basic understanding of the higher plant resources of the world for the successful management of biodiversity requires international collaboration and the setting up of a global taxonomic database. Botanists at all levels should be involved in the taxonomic work, and biologists and conservationists need to be actively aware of the need for such work on a global basis. The database must include census, descriptive, and identification aspects. At present, existing available information is haphazardly distributed on library shelves and inadequately organised. Published data on threatened species have been shown to be hopelessly inaccurate. National and regional Floras may often portray a false perspective of the plants they include. The world's botanists have to organise themselves to pool their information, and substantial international funding is needed to support this. The Species Plantarum Project, set up in 1995 under the International Organisation for Plant Information affiliated to the International Union of Biological Sciences (IUBS), aims to overcome “the taxonomic impediment”, and is currently seeking appropriate funding. It responds to the priorities highlighted in the work programme being developed under the Global Taxonomy Initiative of the Convention on Biological Diversity. The project has an international Steering Committee representing all regions of the world, and aims to develop a further network of collaborators. Publication of data will be in both hard copy and electronic form. Instructions to contributors and accounts of five relatively small families have already been published in hard copy, and accounts of two further families totalling nearly 1000 species are in press. Future plans emphasise the need for capacity building in floristic work throughout the world. The project now invites the collaboration of taxonomists throughout the community, but the future of the project is dependent on funding being made available.
Quasi–stationary distributions in Markov population processes
Authors: Barbour Andrew D. 
Published: April 2006

One way of analysing complicated Markov population processes is to approximate them by a diffusion about the deterministic path. This approximation alone may not, however, answer all the questions which might reasonably be asked. Many processes have phases, for example near boundaries, where a different approximation is required; such processes are better described by a succession of diffusion and special approximations alternately.This paper looks at the special treatment required near a point where the deterministic equations are in equilibrium. When the equilibrium is unstable, the process will eventually wander off, and possibly follow a diffusion around another deterministic path. If the equilibrium is stable, the process will behave as if in stable equilibrium about it for a very much longer time, but may at last be trapped away from it, for instance in an absorbing state. The results presented describe the distributions of the time and place of leaving neighbourhoods of the equilibrium point. The neighbourhoods considered are large enough, in the unstable case, to make possible the link with the next phase of motion. In the stable case, exit times are shown to be so long that the possibility of exit can often be ignored in practice, and the quasi-equilibrium distribution treated as a true equilibrium. A more detailed result, showing how closely the normal approximation holds in this situation, is also provided.
Moment formulas for the Markov renewal branching process
Authors: Neuts Marcel F. 
Published: April 2006

There are many queueing models in which there appears a semi-Markov matrix G(·), whose entries are absorption-time distributions in a Markov renewal branching process. The role of G(·) is similar to that of the busy period in the simple M/G/1 model. The computation of various quantities associated with G(·) is however much more complicated. The moment matrices, and particularly the mean matrix of G(·), are essential in the construction of general and mathematically well-justified algorithms for the steady-state distributions of such queues.This paper discusses the moment matrices of G(·) and algorithms for their numerical computation. Its contents are basic to the algorithmic solutions to several queueing models, which are to be presented in follow-up papers.
An age dependent branching process with variable lifetime distribution
Authors: Fildes Robert 
Published: April 2006

A branching process with variable lifetime distribution is defined by a sequence of distribution functions {Gi(t)}, together with a probability generating function, h(s) = Σk∞= 0pksk. An ith generation particle lives a random length of time, determined by Gi(t). At the end of a particle's life it produces children, the number being determined by h(s). These offspring behave like the initial particle except they are (i + 1)th generation particles and have lifetime distribution Gi + 1 (t).Let Zi(t) be the number of particles alive at time t, the initial particle being born into the ith generation. Integral equations are derived for the moments of Zi(t) and it is shown that for some constants Ni, γ, a, Zi (t)/(Nitγ-1eαt) converges in mean square to a proper random variable.
Limit theorems for stochastic growth models. I
Authors: Kesten Harry 
Published: April 2006

We consider d-dimensional stochastic processes which take values in (R+)d. These processes generalize Galton-Watson branching processes, but the main assumption of branching processes, independence between particles, is dropped. Instead, we assume for some Here τ: (R+)d → R+, |x| = Σ1d |x(i)| A = {x ∈ (R+)d: |x| = 1} and T: A → A. Under various assumptions on the maps τ and T it is shown that with probability one there exists a ρ > 1, a fixed point p ∈ A of T and a random variable w such that limn→∞Znρ−n = wp. This result is a generalization of the main limit theorem for super-critical branching processes; note, however, that in the present situation both p and ρ are random as well. The results are applied to a population genetical model for zygotic selection without mutation at one locus.
Limit laws for maxima of a sequence of random variables defined on a Markov chain
Authors: Resnick Sidney I. , Neuts Marcel F. 
Published: April 2006

Consider the bivariate sequence of r.v.'s {(Jn,Xn),n≧ 0} withX0= - ∞ a.s. The marginal sequence {Jn} is an irreducible, aperiodic,m-state M.C.,m< ∞, and the r.v.'sXnare conditionally independent given {Jn}. FurthermoreP{Jn=j, Xn≦x|Jn− 1=i} =pijHi(x) =Qij(x), whereH1(·), · · ·,Hm(·) are c.d.f.'s. SettingMn= max {X1, · · ·,Xn}, we obtainP{Jn=j, Mn≦x|J0=i} = [Qn(x)]i, j, whereQ(x) = {Qij(x)}. The limiting behavior of this probability and the possible limit laws forMnare characterized.Theorem.Let ρ(x) be the Perron-Frobenius eigenvalue ofQ(x) for realx; then:(a)ρ(x) is a c.d.f.;(b) if for a suitable normalization {Qijn(aijnx+bijn)} converges completely to a matrix {Uij(x)} whose entries are non-degenerate distributions thenUij(x) = πjρU(x), where πj= limn→ ∞pijnand ρU(x) is an extreme value distribution;(c) the normalizing constants need not depend oni, j;(d) ρn(anx+bn) converges completely to ρU(x);(e) the maximumMnhas a non-trivial limit law ρU(x) iffQn(x) has a non-trivial limit matrixU(x) = {Uij(x)} = {πjρU(x)} or equivalently iff ρ(x) or the c.d.f. πi= 1mHiπi(x) is in the domain of attraction of one of the extreme value distributions. Hence the only possible limit laws for {Mn} are the extreme value distributions which generalize the results of Gnedenko for the i.i.d. case.
The asymptotic distribution of random molecules
Authors: Rehder Wulf 
Published: April 2006

If n solid spheres Kn of some volume V(Kn) are scattered randomly in the unit cube of euclidean d-space, some of them will overlap to form Ln(s) molecules with exactly s atoms Kn. The random variable Ln(s) has a limit distribution if V(Kn) tends to zero but nV(Kn) tends to infinity at a certain rate: it is shown that for
Ln(s) is asymptotically Poisson.
Two-armed bandits with a goal, I. One arm known
Authors: Berry Donald A. , Fristedt Bert 
Published: April 2006

One of two random variables, X and Y, can be selected at each of a possibly infinite number of stages. Depending on the outcome, one's fortune is either increased or decreased by 1. The probability of increase may not be known for either X or Y. The objective is to increase one's fortune to G before it decreases to g, for some integral g and G; either may be infinite.In the current part of the paper, the distribution of X is unknown and that of Y is known. We characterize the situations in which optimal strategies exist and, for certain kinds of information concerning X and Y, we characterize optimal sequential strategies for choosing to observe X and Y.In Part II (Berry and Fristedt (1980)), it is known that either X or Y has probability α of increasing the current fortune by 1 and the other has probability β of increasing the fortune by 1, where α and β are known, but which goes with X is not known.
Improved bounds for the availability and unavailability in a fixed time interval for systems of maintained, interdependent components
Authors: Natvig B. 
Published: April 2006

In this paper we arrive at a series of bounds for the availability and unavailability in the time interval I = [tA, tB] ⊂ [0, ∞), for a coherent system of maintained, interdependent components. These generalize the minimal cut lower bound for the availability in [0, t] given in Esary and Proschan (1970) and also most bounds for the reliability at time t given in Bodin (1970) and Barlow and Proschan (1975). In the latter special case also some new improved bounds are given. The bounds arrived at are of great interest when trying to predict the performance process of the system. In particular, Lewis et al. (1978) have revealed the great need for adequate tools to treat the dependence between the random variables of interest when considering the safety of nuclear reactors.Satyanarayana and Prabhakar (1978) give a rapid algorithm for computing exact system reliability at time t. This can also be used in cases where some simpler assumptions on the dependence between the components are made. It seems, however, impossible to extend their approach to obtain exact results for the cases treated in the present paper.
Application of Stieltjes theory forS-fractions to birth and death processes
Authors: Bordes G. , Roehner B. 
Published: April 2006

We are interested in obtaining bounds for the spectrum of the infinite Jacobi matrix of a birth and death process or of any process (with nearest-neighbour interactions) defined by a similar Jacobi matrix.To this aim we use some results of Stieltjes theory forS-fractions, after reviewing them. We prove a general theorem giving a lower bound of the spectrum. The theorem also gives sufficient conditions for the spectrum to be discrete.The expression for the lower bound is then worked out explicitly for several, fairly general, classes of birth and death processes. A conjecture about the asymptotic behavior of a special class of birth and death processes is presented.
Well-timed diffusion approximations
Authors: Walsh John B. 
Published: April 2006

Let X be a Markov process on the line. Under certain conditions it is possible to find a diffusion process which is an approximation to X in the following sense:(1) X can be embedded in that is there are stopping times (Tt) such that {Xt, t ≥ 0} and have the same distribution;(2) for each t, E{Tt} = t.We call the well-timed diffusion approximation to X, and suggest that it is useful for approximating quantities like the first-exit probabilities and expected first-exit times of X.We determine the well-timed approximation in several special cases and give an asymptotic approximation for use in cases in which cannot be exactly determined.
Asymptotic exponentiality of the tail of the waiting-time distribution in a Ph/Ph/C queue
Authors: Takahashi Yukio 
Published: April 2006

It is shown that, in a multiserver queue with interarrival and service-time distributions of phase type (PH/PH/c), the waiting-time distribution W(x) has an asymptotically exponential tail, i.e., 1 – W(x) ∽ Ke–ckx. The parameter k is the unique positive number satisfying T*(ck) S*(–k) = 1, where T*(s) and S*(s) are the Laplace–Stieltjes transforms of the interarrival and the service-time distributions. It is also shown that the queue-length distribution has an asymptotically geometric tail with the rate of decay η = T*(ck). The proofs of these results are based on the matrix-geometric form of the state probabilities of the system in the steady state.The equation for k shows interesting relations between single- and multiserver queues in the rates of decay of the tails of the waiting-time and the queue-length distributions.The parameters k and η can be easily computed by solving an algebraic equation. The multiplicative constant K is not so easy to compute. In order to obtain its numerical value we have to solve the balance equations or estimate it from simulation.
A transition density expansion for a multi-allele diffusion model
Authors: Griffiths R. C. 
Published: April 2006

An expansion in orthogonal polynomials is found for the transition density in a neutral multi-allele diffusion model where the mutation rates of allele typesAi→Ajare assumed to beuj(≥ O). The density is found when the mutation rate is positive for all allele types, and when some or all have zero mutation. The asymptotic conditional density is found for a mixture of positive and zero mutation rates.The infinite alleles limit with equal mutation is studied. Eigenfunctions of the process are derived and the frequency spectrum found. An important result is that the first eigenfunction depends only on the homozygosity.A density for the time to fixation with zero mutation is found for theKallele, and infinite alleles model.
Some properties of a branching process with group immigration and emigration
Authors: Pakes Anthony G. 
Published: April 2006

Batches of immigrants arrive in a region at event times of a renewal process and individuals grow according to a Bellman-Harris branching process. Tribal emigration allows the possibility that all descendants of a group of immigrants collectively leave the region at some instant.A number of results are derived giving conditions for the existence of a limiting distribution for the population size. These conditions can be given either in terms of the immigration distribution or in terms of the distribution of emigration times. Some limit theorems are obtained when the latter conditions are not fulfilled.
Generalizations of the Pollaczek-Khinchin integral equation in the theory of queues
Authors: Neuts Marcel F. 
Published: April 2006

A classical result in queueing theory states that in the stable M/G/1 queue, the stationary distribution W(x) of the waiting time of an arriving customer or of the virtual waiting time satisfies a linear Volterra integral equation of the second kind, of convolution type. For many variants of the M/G/1 queue, there are corresponding integral equations, which in most cases differ from the Pollaczek–Khinchin equation only in the form of the inhomogeneous term. This leads to interesting factorizations of the waiting-time distribution and to substantial algorithmic simplifications. In a number of priority queues, the waiting-time distributions satisfy Volterra integral equations whose kernel is a functional of the busy-period distribution in related M/G/1 queues. In other models, such as the M/G/1 queue with Bernoulli feedback or with limited admissions of customers per service, there is a more basic integral equation of Volterra type, which yields a probability distribution in terms of which the waiting-time distributions are conveniently expressed.For several complex queueing models with an embedded Markov renewal process of M/G/1 type, one obtains matrix Volterra integral equations for the waiting-time distributions or for related vectors of mass functions. Such models include the M/SM/1 and the N/G/1 queues, as well as the M/G/1 queue with some forms of bulk service.When the service-time distributions are of phase type, the numerical computation of waiting-time distributions may commonly be reduced to the solution of systems of linear differential equations with constant coefficients.
Induced rare events: analysis via large deviations and time reversal
Authors: Shwartz Adam , Weiss Alan 
Published: April 2006

When a subsystem goes into an infrequent state, how does the remainder of the system behave? We show how to calculate the relevant distributions using the notions of reversed time for Markov processes and large deviations. For ease of exposition, most of the work deals with a specific queueing model due to Flatto, Hahn, and Wright. However, we show how the theorems may be applied to much more general jump-Markov systems.We also show how the tools of time-reversal and large deviations complement each other to yield general theorems. We show that the way a constant coefficient process approaches a rare event is roughly by following the path of another constant coefficient process. We also obtain some properties, including apriori bounds, for the change of measure associated with some large deviations functionals; these are useful for accelerating simulations.