bluuebunny/crossref_metadata_2025_split huggingface dataset:
The multi-type Galton-Watson process with immigration
Authors: Quine M. P. 
Published: April 2006

SummaryWe consider the limiting behaviour of ak-type (k< ∞) Galton-Watson process which is augmented at each generation by a stochastic immigration component. In Section 2, conditions for ergodicity are found for a subclass of such processes. In Section 3, expressions are derived for the first two moments of thenth generation (by way of a recurrence relation) and for the first two asymptotic moments, in a manner which to some extent generalises previous results.
Demographic effects on the rate of genetic evolution I. constant size populations with two genotypes
Authors: Chia A.B. , Watterson G. A. 
Published: April 2006

SummaryA model is constructed to describe the evolution of a monoecious haploid population in which the population of adults remains of constant size, but for which generations may be overlapping, family size distributions are to a considerable degree arbitrary, and differential survival rates may apply with respect to adult and young individuals. The eigenvalues of the transition probability matrix are obtained, and those which determine the rate of evolution are found as simple functions of mutation rates, the mean lifetime of an individual, and the variance of his viable offspring number. The model builds on, and includes as special cases, certain non-overlapping generation models of Wright (1931), Karlin and McGregor (1965), and an overlapping generation model of Moran (1958).One of the secondary conclusions of the study is that for some models, when evolutionary rates are measured on a mean-lifetime scale, the more offspring that are produced at a mating season may slow down evolution when mutation is absent, but may speed it up if mutation is present.
Random secants of a convex body
Authors: Kingman J. F. C. 
Published: April 2006

SummaryLet two points be taken at random in an n-dimensional convex body K, and let σ be the line joining them. The distribution of σ is found and compared with other distributions for random secants of K. More generally, if r + 1 ≦ npoints are taken in K, the distribution of the r-dimensional affine subspace containing them is computed. The results find application to the n-dimensional case of a problem of Sylvester.
Distribution of the branching-process population among generations
Authors: Samuels M. L. 
Published: April 2006

SummaryIn a standard age-dependent branching process, let Rn(t) denote the proportion of the population belonging to the nth generation at time t. It is shown that in the supercritical case the distribution {Rn(t); n = 0, 1, …} has asymptotically, for large t, a (non-random) normal form, and that the mean ΣnRn(t) is asymptotically linear in t. Further, it is found that, for large n, Rn(t) has the shape of a normal density function (of t).Two other random functions are also considered: (a) the proportion of the nth generation which is alive at time t, and (b) the proportion of the nth generation which has been born by time t. These functions are also found to have asymptotically a normal form, but with parameters different from those relevant for {Rn(t)}.For the critical and subcritical processes, analogous results hold with the random variables replaced by their expectations.
Interconnected birth and death processes
Authors: Puri Prem S. 
Published: April 2006

SummaryTwo cases of multiple linearly interconnected linear birth and death processes are considered. It is found that in general the solution of the Kolmogorov differential equations for the probability generating function (p.g.f)gof the random variables involved is not obtainable by standard methods, although one can obtain moments of the random variables from these equations. A method is considered for obtaining an approximate solution forg.This is based on the introduction of a sequence of stochastic processes such that the sequence {f(n)} of their p.g.f.'s tends togasn → ∞in an appropriate manner. The method is applied to the simple case of two birth and death processes with birth and death rates λiandμi, i =1,2, interconnected linearly with transition rates v andδ(see Figure 2). For this case some limit theorems are established and the probability of ultimate extinction of both the processes is considered. In addition, for the special cases (i) λ1=δ= 0, with the remaining rates time dependent and (ii) λ2=δ= 0, with the remaining rates constant, explicit solutions forgare obtained and studied.
Characterizations of the normal distribution by suitable transformations
Authors: Beer S. , Lukacs E. 
Published: April 2006

Yu. V. Linnik showed that certain transformations, given by Formulae (1.1), (1.6) and (1.7) transform a normal sample into itself. The transformations (1.1) and (1.7) apply to samples of size 2 while (1.6) admits an arbitrary sample size. It is also assumed that the population mean is zero.In the present paper the converse theorems are proven so that characterizations of the normal distribution are obtained. The problem leads to the functional equations (2.3) and (2.13) whose solution yields the desired results.
Conditional moments in a critical age-dependent branching process
Authors: Weiner Howard J. 
Published: April 2006

Let X(t), N(t) respectively denote the number of cells alive at t and the total number of cells born by t in a critical age-dependent Bellman-Harris branching process.The asymptotic behavior of the conditional moments, for 0 < α ≦ 1, E(Nn(αt) | X(t) > 0), E(Nn(t) |X(αt) > 0), is obtained.
Some new integral geometric formulae, with stochastic applications
Authors: Miles R. E. 
Published: April 2006

Alternative forms of the integral geometric density of an r-subspace [r-flat] containing q[q + 1] points in euclidean n-space Rn are given Stochastic applications in R3 include formulae for(i) the mean area of intersection of a domain by an isotropic plane through the origin; and(ii) the variance of the area of intersection of a domain by an isotropic uniform plane.
Extremal properties of the FIFO discipline in queueing networks
Authors: Righter Rhonda , Shanthikumar J. George 
Published: April 2006

We show that using the FIFO service discipline at single server stations with ILR (increasing likelihood ratio) service time distributions in networks of monotone queues results in stochastically earlier departures throughout the network. The converse is true at stations with DLR (decreasing likelihood ratio) service time distributions. We use these results to establish the validity of the following comparisons:(i) The throughput of a closed network of FIFO single-server queues will be larger (smaller) when the service times are ILR (DLR) rather than exponential with the same means.(ii) The total stationary number of customers in an open network of FIFO single-server queues with Poisson external arrivals will be stochastically smaller (larger) when the service times are ILR (DLR) rather than exponential with the same means.We also give a surprising counterexample to show that although FIFO stochastically maximizes the number of departures by any time t from an isolated single-server queue with IHR (increasing hazard rate, which is weaker than ILR) service times, this is no longer true for networks of more than one queue. Thus the ILR assumption cannot be relaxed to IHR.Finally, we consider multiclass networks of exponential single-server queues, where the class of a customer at a particular station determines its service rate at that station, and show that serving the customer with the highest service rate (which is SEPT — shortest expected processing time first) results in stochastically earlier departures throughout the network, among all preemptive work-conserving policies. We also show that a cµ rule stochastically maximizes the number of non-defective service completions by any time t when there are random, agreeable, yields.
Forward and backward processes in bisexual models with fixed population sizes
Authors: Möhle M. 
Published: April 2006

This paper introduces exchangeable bisexual models with fixed population sizes and non-overlapping generations. In each generation there are N pairs of individuals consisting of a female and a male. The N pairs of a generation produce N daughters and N sons altogether, and these 2N children form the N pairs of the next generation at random.First the extinction of the lines of descendants of a fixed number of pairs is studied, when the population size becomes large. Under suitable conditions this structure can be approximately treated in the framework of a Galton-Watson process. In particular it is shown for the Wright-Fisher model that the discrepancy between the extinction probabilities in the model and in the approximating Galton-Watson process is of order N.Next, the process of the number of ancestor-pairs of all pairs of a generation is analysed. Under suitable conditions this process, properly normed, has a weak limit as N becomes large. For the Wright-Fisher model this limit is an Ornstein–Uhlenbeck process (restricted to a discrete time-set). The corresponding stationary distributions of the backward processes converge to the normal distribution, as expected.
Stochastic vector difference equations with stationary coefficients
Authors: Glasserman Paul , Yao David D. 
Published: April 2006

We give a unified presentation of stability results for stochastic vector difference equationsbased on various choices of binary operationsand, assuming thatare stationary and ergodic. In the scalar case, under standard addition and multiplication, the key condition for stability isE[log |A0|] < 0. In the generalizations, the condition takes the form γ< 0, where γis the limit of a subadditive process associated with. Under this and mild additional conditions, the processhas a unique finite stationary distribution to which it converges from all initial conditions.The variants of standard matrix algebra we consider replace the operations + and × with (max, +), (max,×), (min, +), or (min,×). In each case, the appropriate stability condition parallels that for the standard recursions, involving certain subadditive limits. Since these limits are difficult to evaluate, we provide bounds, thus giving alternative, computable conditions for stability.
Super-extremal processes and the argmax process
Authors: Resnick Sidney I. , Roy Rishin 
Published: April 2006

In this paper, we develop the probabilistic foundations of the dynamic continuous choice problem. The underlying choice set is a compact metric space E such as the unit interval or the unit square. At each time point t, utilities for alternatives are given by a random function . To achieve a model of dynamic continuous choice, the theory of classical vector-valued extremal processes is extended to super-extremal processesY= {Yt, t > 0}. At any t > 0, Yt is a random upper semicontinuous function on a locally compact, separable, metric space E. General path properties of Y are discussed and it is shown that Y is Markov with state-space US(E). For each t > 0, Yt is associated.For a compact metric E, we consider the argmax process M = {Mt, t > 0}, where . In the dynamic continuous choice application, the argmax process M represents the evolution of the set of random utility maximizing alternatives. M is a closed set-valued random process, and its path properties are investigated.
Disulfide Conjugation of Peptides to Oligonucleotides and Their Analogs
Authors: Turner John J. , Williams Donna , Owen David , Gait Michael J. 
Published: April 2006

AbstractPeptide conjugation of oligonucleotides and their analogs is being studied widely towards improving the delivery of oligonucleotides into cells. Amongst the many possible routes of conjugation, the disulfide linkage has proved to be the most popular. This reversible linkage may have advantages for cell delivery, since it is likely to be cleaved within cells, thus releasing the oligonucleotide cargo. It is straightforward to introduce thiol functionalities into both oligonucleotide and peptide components suitable for disulfide conjugation. However, severe difficulties have been encountered in carrying out conjugations between highly cationic peptides and negatively charged oligonucleotides because of aggregation and precipitation. Presented here are reliable protocols for disulfide conjugation that have been verified for both cationic and hydrophobic peptides as well as oligonucleotides containing deoxyribonucleosides, ribonucleosides, 2′‐O‐methylribonucleosides, locked nucleic acid (LNA) units, as well as phosphorothioate backbones. Also presented are reliable protocols for disulfide conjugation of peptide nucleic acids (PNAs) with peptides.
Using the Structure‐Function Linkage Database to Characterize Functional Domains in Enzymes
Authors: Brown Shoshana , Babbitt Patricia 
Published: April 2006

AbstractThe Structure‐Function Linkage Database (SFLD; http://sfld.rbvi.ucsf.edu/) is a Web‐accessible database designed to link enzyme sequence, structure, and functional information. This unit describes the protocols by which a user may query the database to predict the function of newly sequenced enzymes and to correct misannotated functional assignments for enzymes currently in public databases. It is especially useful in helping a user discriminate functional capabilities of a sequence that is only distantly related to characterized sequences in publicly available databases.
Using Pharmabase to Perform Pharmacological Analyses of Cell Function
Authors: Smith Peter J. S. , Remsen David 
Published: April 2006

AbstractPharmabase is designed to form a bridge between the molecular dimension of cell transport processes and the functional manipulation of the protein players. It has as its emphasis membrane transport and related pharmacology. Several search and navigation options are available, including membrane transport, disease, and a graphic interface arranged by pathway and cell type. The level of entry to the database can be tailored to the investigator's level of expertise. The final product of Pharmabase is a Compound Record detailing the use and targets of individual compounds. Navigation routes generally fall into hierarchical keys and are cross‐referenced. Pharmabase encourages input from its user community. It is maintained by the BioCurrents Research Center, an NIH resource funded through the National Center for Research Resources (NCRR).
Do surrogates describe patterns in marine macroalgal diversity in the Recherche Archipelago, temperate Australia?
Authors: Goldberg Nisse A. , Kendrick Gary A. , Walker Diana I. 
Published: April 2006

Abstract
Surrogates aim to predict species diversity and to minimize sampling effort. Here the value of surrogates for marine macroalgae is tested.
Higher taxonomic levels and dominant taxa were evaluated as surrogates for detecting patterns in macroalgal species diversity (derived from species‐level biomass data) in the Recherche Archipelago, Western Australia.
Data were stratified by two island groups (inshore and offshore), three depth intervals (<10 m, 10–20 m, >20 m), and two exposures to wave energy. Correlations between similarity matrices from surrogate and species diversity data matrices were analysed using a modified Spearman rank correlation (rs). The ability of surrogates to detect differences between exposures to wave energy was also investigated using analysis of similarity. Species diversity data were aggregated to higher taxonomic levels and were either fourth‐root or presence/absence (richness) transformed.
Species richness was the most consistent surrogate (rs‐values>0.69, P=0.001). Genus‐level richness was also strongly correlated to species diversity in the Recherche Archipelago, except in depths <10 m where patterns in diversity were characterized by species turnover.
At offshore islands in depths 10–20 m and >20 m, family‐ and order‐level biomass data were suitable surrogates owing to the abundance of Alariaceae (Order Laminariales) represented by a single genus and species. Surrogates using biomass data from the orders Laminariales, Ceramiales, Dictyotales and Fucales were also successful at offshore islands in middle to deeper depths.
At inshore islands in depths 10–20 m and >20 m, genera from the orders Gigartinales, Fucales and Ceramiales were strongly correlated to species biomass data.
Surrogates, like species richness, that were strongly correlated to species biomass data were also able to distinguish between exposures to wave energy, based on analysis of similarity tests.
Sampling effort would be reduced if collecting richness data in species‐rich macroalgal assemblages such as those found in temperate Australia.
Copyright © 2006 John Wiley & Sons, Ltd.
Altered thymocyte migration during experimental acute Trypanosoma cruzi infection: combined role of fibronectin and the chemokines CXCL12 and CCL4
Authors: Mendes‐da‐Cruz Daniella Arêas , Silva João Santana , Cotta‐de‐Almeida Vinícius , Savino Wilson 
Published: April 2006

AbstractWe previously showed migration disturbances in the thymus during experimental infection with Trypanosoma cruzi, the causative agent of Chagas disease. These changes were related to the enhanced expression of extracellular matrix ligands and receptors, leading to the escape of immature cells to the periphery. Here, we analyzed the expression and role of selected chemokines (CXCL12 and CCL4) and their receptors (CXCR4 and CCR5) in regulating thymocyte migration in conjunction with extracellular matrix during acute T. cruzi infection. We found increased chemokine deposition in the thymus of infected mice when compared to controls, accompanied by enhanced co‐localization with fibronectin as well as up‐regulated surface expression of CXCR4 and CCR5 in thymocytes. We also noticed altered thymocyte migration towards the chemokines analyzed. Such an enhancement was even more prominent when fibronectin was added as a haptotatic stimulus in combination with a given chemokine. Our findings suggest that thymocyte migration results from a combined action of chemokines and extracellular matrix (ECM), which can be altered during pathological conditions such as T. cruzi infection, and may be at the origin of the changes in the T cell repertoire seen in this pathological process.
Toward high sequence coverage of proteins in human breast cancer cells using on‐line monolith‐based HPLC‐ESI‐TOF MS compared to CE MS
Authors: Yoo Chul , Pal Manoj , Miller Fred R. , Barder Timothy J. , Huber Christian , Lubman David M. 
Published: April 2006

AbstractA method is developed toward high sequence coverage of proteins isolated from human breast cancer MCF10 cell lines using a 2‐D liquid separations. Monolithic‐capillary columns prepared by copolymerizing styrene with divinylbenzene are used to achieve high‐resolution separation of peptides from protein digests. This separation is performed with minimal sample preparation directly from the 2‐D liquid fractionation of the cell lysate. The monolithic column separation is directly interfaced to ESI‐TOF MS to obtain a peptide map. The protein digests were also analyzed by MALDI‐TOF MS and an accurate Mr of the intact protein was obtained using an HPLC‐ESI‐TOF MS. The result is that these techniques provide complementary information where nearly complete sequence coverage of the protein is obtained and can be compared to the experimental Mr value. The high sequence coverage provides information on isoforms and other post‐translational modifications that would not be available from methods that result in low sequence coverage. The results from the use of monolithic columns are compared to that obtained by CE‐MS. The monolithic column separations provide a rugged and highly reproducible method for separating protein digests prior to MS analysis and is suited to confidently identify biomarkers associated with cancer progression.
Analysis of choline and atropine in hairy root cultures of Cannabis sativa L. by capillary electrophoresis‐electrospray mass spectrometry
Authors: Wahby Imane , Arráez‐Román David , Segura‐Carretero Antonio , Ligero Francisco , Caba Juan Manuel , Fernández‐Gutiérrez Alberto 
Published: April 2006

AbstractWe describe a capillary zone electrophoresis method coupled to electrospray ionization (ion trap) mass spectrometry (CZE‐ESI‐MS) for the identification and determination of choline and atropine compounds in hairy root extracts from Cannabis sativa L. Fused‐silica capillary and an alkaline solution of 20 mM ammonium acetate at pH 8.5 are used being the most suitable for the analysis of choline and atropine in less than 10 min. Under the optimized conditions, including CE and ESI‐MS parameters, the method resolved both compounds with very high sensitivity. The system exhibited good linear response in the range of 25–500 mg/L and 500–1000 μg/L for choline and atropine, respectively. The detection limit of choline was 18 mg/L and 320 μg/L for atropine. Finally, the developed method was applied to the analysis of these compounds in transgenic root cultures of Cannabis sativa L.
Laser‐deposited Ti‐Nb‐Zr‐Ta orthopedic alloys
Authors: Banerjee R. , Nag S. , Samuel S. , Fraser H.L. 
Published: April 2006

AbstractThe complex quaternary Ti‐35Nb‐7Zr‐5Ta orthopedic alloy has been successfully deposited from a powder feedstock consisting of a blend of elemental titanium, niobium, zirconium, and tantalum powders, using the laser engineered net‐shaping (LENS™) process. In the as laser‐deposited form, these alloys exhibit a substantially higher tensile strength as compared with more conventionally processed counterparts of similar composition, while maintaining excellent ductility and a low modulus. Furthermore, the as‐deposited alloys appear to exhibit a <001> texture, with a substantially large number of grains of the β phase aligning one of their <001> axes nearly normal to the substrate or parallel to the growth direction. The microstructure of the as‐deposited as well as tensile‐tested alloys have been characterized in detail using scanning electron microscopy (SEM), orientation microscopy (OM), and transmission electron microscopy (TEM). Formation of a high density of shear bands, possibly arising from slip localization due to precipitates of the ω phase in the β matrix, is clearly evident in the tensile‐tested sample. The enhanced tensile strength and low modulus in these laser‐deposited alloys coupled with the ability to form near‐net shape components makes LENS an attractive processing technology for orthopedic implants. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Comparison of conventional and highly crosslinked UHMWPE patellae evaluated by a new in vitro patellofemoral joint simulator
Authors: Burroughs Brian R. , Rubash Harry E. , Estok Daniel , Jasty Murali , Krevolin Janet , Muratoglu Orhun K. 
Published: April 2006

AbstractA series of in vitro patella damage tests were developed using a knee simulator to investigate electron‐beam‐irradiated and ‐melted ultra‐high molecular weight polyethylene and conventional ultra‐high molecular weight polyethylene at the patellofemoral articulation. Three different simulations were created: (i) normal gait with optimal component alignment, (ii) stair climbing with optimal component alignment, and (iii) stair climbing with 4° of femoral component internal rotation to simulate a component malalignment condition. In the last two simulations, all patellae were artificially aged. In normal gait, the unaged conventional and highly crosslinked patellae demonstrated similar behavior. In both stair climbing tests, unlike the aged highly crosslinked components, the aged conventional patellae developed cracks by 2 million cycles. These results demonstrate the potential advantage of highly crosslinked polyethylene for the patella. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006