bluuebunny/crossref_metadata_2025 huggingface dataset:
On up- and downcrossings
Authors: Cohen J. W.
Published: April 2006

For the sample functions of the stationary virtual waiting-time process vt of the GI/G/1 queueing system some properties of the number of up- and downcrossings of level v by the vt-process during a busy cycle are investigated. It turns out that the simple fact that this number of upcrossings is equal to that of downcrossings leads in a rather easy way to basic relations for the waiting-time distributions. This approach to the study of the vt-process of the GI/G/1 system seems to be applicable to many other types of stochastic processes. As another example of this approach the infinite dam with non-constant release rate is briefly discussed.
Availability measures for a two-state system
Authors: Baxter Laurence A.
Published: April 2006

The use of alternating renewal processes to model the behaviour of a repairable system is discussed, and properties of two measures of availability are reviewed. It is shown how the introduction of forward recurrence times to failure enables these measures to be generalised.
The application of the Hankel transformation to spherically symmetric coverage problems
Authors: Schroeter Gerhard
Published: April 2006

We derive an integral expression for the expected coverage of an n-dimensional target when the value density function of the target, the damage function, and the distribution of the damage function center around the target center are spherically symmetric. This integral expression is transformed by means of Parseval's theorem for Hankel transforms to an integral of the product of the Hankel transforms of order ½n − 1 of all underlying functions.
Diffusion approximations to linear stochastic difference equations with stationary coefficients
Authors: Guess Harry A. , Gillespie John H.
Published: April 2006

It is shown that solutions to linear first-order stochastic difference equations with stationary autocorrelated coefficients converge weakly inD[0,1] to an Ito stochastic integral plus a correction term when the time scale is shifted so that the means, variances, and covariances of the coefficients all approach zero at the same rate. Other limit theorems applicable to different time scale shifts are also given. These results yield two different continuous time limits to a recent model of Roughgarden (1975) for population growth in stationary random environments. One limit, an Ornstein-Uhlenbeck process, is applicable in the presence of rapidly fluctuating autocorrelated environments; the other limit, which is not a diffusion process, applies to the case of slowly varying, highly autocorrelated environments. Other applications in population biology and genetics are discussed.
Optimality of the shortest line discipline
Authors: Winston Wayne
Published: April 2006

We consider a queuing system consisting of a finite number of identical exponential servers. Each server has its own queue, and upon arrival each customer must be assigned to some server's queue. Under the assumption that no jockeying between queues is permitted, it is shown that the intuitively satisfying rule of assigning each arrival to the shortest line maximizes, with respect to stochastic order, the discounted number of customers to complete their service in any time t.
A generalization of a result of Erdös and Rényi
Authors: Kaplan Norman
Published: April 2006

Consider a finite urn scheme with balls uniformly distributed amongst the urns. Using a technique of Karlin, the asymptotic behavior of the number of throws necessary to obtain at least m (m ≧ 1) balls in a given fraction of the urns is studied.
Regenerative sets and subordinators
Authors: Gzyl Cristina
Published: April 2006

It has been shown that the probabilistic structure of a regular regenerative set can be described in terms of the exponent of an appropriate subordinator. We give a relation which expresses the distribution of two Markov processes associated with a regenerative set in terms of this exponent.
Evaluation of the first-passage time probability to a square root boundary for the Wiener process
Authors: Sato Shunsuke
Published: April 2006

This paper gives an asymptotic evaluation of the probability that the Wiener path first crosses a square root boundary. The result is applied to estimate the moments of the first-passage time distribution of the Ornstein–Uhlenbeck process to a constant boundary.
On the random coverage of the circle
Authors: Holst L. , Hüsler J.
Published: April 2006

Place n arcs of equal length a uniformly at random on the circumference of a circle. We discuss the joint limit distributions of the number of gaps, the uncovered proportion of the circle and the lengths of the largest gap and of the smallest gap, depending on how a → 0 as n →∞.

We show that the results may be proved in a unified and simple way by using a result of Le Cam.
Evolutionarily stable strategies of diploid populations with semi-dominant inheritance patterns
Authors: Cressman R. , Hines W. G. S.
Published: April 2006

The assumption of arbitrary and biologically implausible inheritance patterns in sexual diploid populations can yield population models in which convergence of a population's mean strategy to an evolutionarily stable strategy will not occur, even though this strategy is attainable with the correct choice of gametic frequencies. The present paper investigates the effect of imposing a simplifying and biologically reasonable restriction on the assumed inheritance patterns; namely, that dominance or underdominance occurs.
The queue GI/Hm/s in continuous time
Authors: De smit Jos H. A.
Published: April 2006

This is an extension of our previous paper [4] on the queue GI/Hm/s. In that paper we have derived results for the actual waiting time, the number of customers in the system at arrival epochs and the number of customers during a busy cycle. Here we obtain results for the virtual waiting time and the number of customers in the system at arbitrary times.
Coupling methods and the storage equation
Authors: Kendall Wilfrid S.
Published: April 2006

Coupling methods are applied to the study of the storage equation with stationary input. Results on the existence of statistical equilibria are obtained. Means of obtaining rate-of-convergence estimates are indicated.
The variance of discounted Markov decision processes
Authors: Sobel Matthew J.
Published: April 2006

Formulae are presented for the variance and higher moments of the present value of single-stage rewards in a finite Markov decision process. Similar formulae are exhibited for a semi-Markov decision process. There is a short discussion of the obstacles to using the variance formula in algorithms to maximize the mean minus a multiple of the standard deviation.
Estimating volumes from systematic hyperplane sections
Authors: Cruz-Orive Luis-M.
Published: April 2006

A theory for volume estimation from independent, unbounded plane probes is available. In practice, however, probes cannot be unbounded and independent at the same time, hence the interest of systematic sectioning. Previous empirical studies on real specimens showed that the mean square error of a volume ratio estimator obtained from m systematic sections behaved roughly as m–3 for small m. This drastic increase in efficiency with respect to independent sectioning prompted us to develop some theoretical models in this paper. We study specimens consisting of two ellipsoids in Rn. In virtue of an invariance result, an ellipsoid–ellipsoid model can be studied via a simple model consisting of two concentric n-balls. Explicit results are obtained for n = 1 and n = 3. In the latter case the bias and the mean square error of the relevant volume ratio estimator are both shown to be of O (m–4).
The optimal value of markov stopping problems with one-step look ahead policy
Authors: Yasuda Masami
Published: April 2006

This paper treats stopping problems on Markov chains in which the OLA (one-step look ahead) policy is optimal. Its associated optimal value can be explicitly expressed by a potential for a charge function of the difference between the immediate reward and the one-step-after reward. As an application to the best choice problem, we shall obtain the value of three problems: the classical secretary problem, a problem with a refusal probability and a problem with a random number of objects.
Remarks on the maxima of a martingale sequence with application to the simple critical branching process
Authors: Pakes Anthony G.
Published: April 2006

Let where {Zn, ℱn} is a non-negative submartingale satisfying Ei(Zn log Zn) →∞. It is shown that

When {Zn} is a simple critical Galton–Watson process and is slowly varying at∞, conditions are given ensuring that

This gives an alternative proof of a result recently established by Kammerle and Schuh.
The waiting-time process of a queueing system with gamma-type input and blocking
Authors: Langaris C.
Published: April 2006

In this work the first-come-first-served waiting-time process of a customer in a two-stage queueing network without intermediate waiting space is analysed. We assume that the arrivals follow the gamma distribution, the service times in the first stage are arbitrarily distributed, and the service times in the second stage are again of gamma type.

Connecting the waiting time of the (n + 1)th customer with that of the nth and locating the zeros of a certain function we derive expressions for the Laplace transform of the waiting-time distribution both in the transient and the steady state.
Stochastic models in cell kinetics
Authors: Brockwell Peter J.
Published: April 2006

We discuss the role of stochastic processes in modelling the life-cycle of a biological cell and the growth of cell populations. Results for multiphase age-dependent branching processes have proved invaluable for the interpretation of many of the basic experimental studies of the life-cycle. Moreover problems from cell kinetics, in particular those related to diurnal rhythm in cell-growth, have stimulated research into ‘periodic' renewal theory, and the asymptotic behaviour of populations of cells with periodic death rate.
Some discrete distributions associated with orthogonal polynomials
Authors: Watson Geoffrey S.
Published: April 2006

Five distributions on the non-negative integers are given which use the orthogonal polynomials of Hermite, Legendre, Laguerre and Chebyshev.
First-passage-time density and moments of the ornstein-uhlenbeck process
Authors: Ricciardi Luigi M. , Sato Shunsuke
Published: April 2006

A detailed study of the asymptotic behavior of the first-passage-time p.d.f. and its moments is carried out for an unrestricted conditional Ornstein-Uhlenbeck process and for a constant boundary. Explicit expressions are determined which include those earlier discussed by Sato [15] and by Nobile et al. [9]. In particular, it is shown that the first-passage-time p.d.f. can be expressed as the sum of exponential functions with negative exponents and that the latter reduces to a single exponential density as time increases, irrespective of the chosen boundary. The explicit expressions obtained for the first-passage-time moments of any order appear to be particularly suitable for computation purposes.
The steady-state distribution of spent service times present in theM/G/1 foreground–background processor-sharing queue
Authors: Schassberger R.
Published: April 2006

The steady-state distribution of spent service times present in theM/G/1 foreground-background processor-sharing queue is described by a random measure, whose generating functional is obtained.
Rates of Poisson convergence for some coverage and urn problems using coupling
Authors: Holst L. , Kennedy J. E. , Quine M. P.
Published: April 2006

Bounds on the rate of convergence measured by the variation distance are obtained for the number of large spacings and for two occupancy problems connected with multinomial and Pólya sampling. The bounds are derived by imbedding techniques together with the elementary coupling inequality.
On some statistics connected with runs in Markov chains
Authors: Banjević Dragan
Published: April 2006

We consider a class of statistics connected with the history of a Markov chain before the first occurrence of certain runs. Methods for deriving generating functions, distributions and moments of the statistics considered are given. In the case of i.i.d. random variables, explicit formulas are derived.
A random allocation model for carrier-borne epidemics
Authors: Daley D. J. , Gani J.
Published: April 2006

A carrier-borne epidemic is considered in which the carriers, subject to a death process, infect susceptibles by random allocation rather than the classical homogeneous mixing process. An explicit solution for the probability generating function (p.g.f.) of the process is obtained, and a probabilistic analysis of carrier models provided. The sizes and durations of the random allocation and classical carrier epidemics are compared. The strongest comparisons concern sample path results based on the probabilistic analysis; this also gives a sounder basis for computational work.
A new approach to (s, S) inventory systems
Authors: Hu Jian-Qiang , Nananukul Soracha , Gong Wei-Bo
Published: April 2006

In this paper, we consider period review (s, S) inventory systems with independent and identically distributed continuous demands and full backlogging. Using an approach recently proposed by Gong and Hu (1992), we derive an infinite system of linear equations for all moments of inventory level. Based on this infinite system, we develop two algorithms to calculate the moments of the inventory level. In the first one, we solve a finite system of linear equations whose solution converges to the moments as its dimension goes to infinity. In the second one, we in fact obtain the power series of the moments with respect to s and S. Both algorithms are based on some very simple recursive procedures. To show their efficiency and speed, we provide some numerical examples for the first algorithm.

(s, S) INVENTORY SYSTEMS; DYNAMIC RECURSIVE EQUATIONS; INFINITE LINEAR EQUATIONS; MACLAURIN SERIES
Geometric bounds on iterative approximations for nearly completely decomposable Markov chains
Authors: Louchard Guy , Latouche Guy
Published: April 2006

We consider a finite Markov chain with nearly-completely decomposable stochastic matrix. We determine bounds for the error, when the stationary probability vector is approximated via a perturbation analysis.
A construction for multi-modal processes, and a potential memory device
Authors: Whittle P.
Published: April 2006

It is shown that if parameters occurring linearly in the transition intensity of a Markov process are replaced by their respective ‘Bayesian estimates' then the new process thus generated has an equilibrium distribution which is a mixture (over parameter values) of the original parametrised equilibrium distribution.

One effectively then has an extra state dependence in that one selects from a given class of transition rules those rules which are most consistent with the value of current state. The effect of this is thus to preserve the status quo, in that unlikely transitions are made even less likely. By this means one can construct processes which show several distinct and metastable modes of behaviour, and which can serve as models for memory devices.
Some estimates of the rate of convergence for birth and death processes
Authors: Zeifman A. I.
Published: April 2006

The ergodic properties of birth and death processes are studied. We obtain some explicit estimates for the rate of convergence by the methods of theory of differential equations.
A stochastic ordering of partial sums of independent random variables and of some random processes
Authors: Boland Philip J. , Proschan Frank , Tong Y. L.
Published: April 2006

In this paper we first prove an arrangement-decreasing property of partial sums of independent random variables when they are partially ordered through the likelihood ratio ordering. We then apply a similar argument to obtain a stochastic ordering of random processes via a comparison of their parameter functions, with special applications to Poisson and Wiener processes. Finally, in Section 4 we present some applications in reliability theory, queueing, and first-passage problems.
The mean waiting time of a GI/G/1 queue in light traffic via random thinning
Authors: Nananukul Soracha , Gong Wei-Bo
Published: April 2006

In this paper, we derive the MacLaurin series of the mean waiting time in light traffic for a GI/G/1 queue. The light traffic is defined by random thinning of the arrival process. The MacLaurin series is derived with respect to the admission probability, and we prove that it has a positive radius of convergence. In the numerical examples, we use the MacLaurin series to approximate the mean waiting time beyond light traffic by means of Padé approximation.
On the solution of Kac-type partial differential equations
Authors: Arató Mátyás
Published: April 2006

The Cauchy problem in the form of (1.11) with linear and constant coefficients is discussed. The solution (1.10) can be given in explicit form when the stochastic process is a multidimensional autoregression (AR) type, or Ornstein–Uhlenbeck process. Functionals of (1.10) form were studied by Kac in the Brownian motion case. The solutions are obtained with the help of the Radon–Nikodym transformation, proposed by Novikov [12].
On a random vibration model
Authors: Huang Dawei , Spencer N. M.
Published: April 2006

A random vibration model is investigated in this paper. The model is formulated as a cosine function with a constant frequency and a random walk phase. We show that this model is second-order stationary and can be rewritten as a vector-valued AR(1) model as well as a scalar ARMA(2, 1) model. The linear innovation sequence of the AR(1) model is shown to be a martingale difference sequence while the linear innovation sequence of the ARMA(2, 1) model is only an uncorrelated sequence. A non-linear predictor is derived from the AR(1) model while a linear predictor is derived from the ARMA(2, 1) model. We deduce that the non-linear predictor of this model has less mean square error than that of the linear predictor. This has significance, for example, for predicting seasonal phenomena with this model. In addition, the limit distributions of the sample mean, the finite Fourier transforms and the autocovariance functions are derived using a martingale approach. The limit distribution of autocovariance functions differs from the classical result given by Bartlett's formula.
An infinite variance solidarity theorem for Markov renewal functions
Authors: Sgibnev M. S.
Published: April 2006

Let , be a recurrent Markov renewal process and Mik(t) be the expected value of Nk(t) provided that at the initial moment the system is in state i. It is shown that when the mean recurrence times μ ii are finite, the differences μ ij Mki (t) – t behave asymptotically the same for all states i and k.
On simulation of random vectors by given densities in regions and on their boundaries
Authors: Borovkov K. A.
Published: April 2006

We suggest a new universal method of stochastic simulation, allowing us to generate rather efficiently random vectors with arbitrary densities in a connected open region or on its boundary. Our method belongs to the class of dynamic Monte Carlo procedures and is based on a special construction of a Markov chain on the boundary of the region. Its remarkable feature is that this chain admits a simple simulation, based on a universal (depending only on the dimensionality of the space) stochastic driver.
Time series models with univariate margins in the convolution-closed infinitely divisible class
Authors: Joe Harry
Published: April 2006

A unified way of obtaining stationary time series models with the univariate margins in the convolution-closed infinitely divisible class is presented. Special cases include gamma, inverse Gaussian, Poisson, negative binomial, and generalized Poisson margins. ARMA time series models obtain in the special case of normal margins, sometimes in a different stochastic representation. For the gamma and Poisson margins, some previously defined time series models are included, but for the negative binomial margin, the time series models are different and, in several ways, better than previously defined time series models. The models are related to multivariate distributions that extend a univariate distribution in the convolution-closed infinitely divisible class. Extensions to the non-stationary case and possible applications to modelling longitudinal data are mentioned.
Receptors as Drug Targets
Authors: Williams Michael , Raddatz Rita
Published: April 2006

Receptors, located on both the cell surface and within the cell, are the molecular targets through which drugs produce their beneficial effects in various disease states. Receptors were initially conceptualized at the beginning of the 20th century by the parallel efforts of Ehrlich and Langley. The concepts of the receptor and receptor theory, based on the Law of Mass Action, have undergone continuous refinement as they have been characterized in terms of their molecular structure, association with ancillary proteins (e.g., G proteins, arrestins, RAMPs), and functional characteristics in normal and diseased tissues. The concepts describing ligand interactions with receptors have also been refined from the simple binary concept of competitive agonists and antagonists to partial agonists, allosteric modulators and inverse agonists. Concepts such as receptor constitutive activity, internalization and dimerization add additional complexity to the role of receptors in tissue function and in precisely characterizing their role in homeostasis and disease.
Testing for Inverse Agonism with Constitutive Receptor Systems
Authors: Kenakin Terry
Published: April 2006

This unit discusses the use of constitutive 7‐transmembrane/G protein coupled receptor (7TM/GPCR) activity for screening new drug entities. Following an introduction to constitutive 7TM/GPCR activity, the unit centers on the three basic components of a constitutive screening system: the receptor, the receptor coupling components (G protein), and the response reporting system. The design of specific assays to detect inverse agonism and the application of such systems to drug screening are also discussed. Finally, the relative advantages and disadvantages of inverse agonists as therapeutic agents are considered.
Isolation of GLUT4 Storage Vesicles
Authors: Kandror Konstantin V. , Pilch Paul F.
Published: April 2006

The immunoisolation of GLUT4‐containing vesicles from adipocytes is described in this unit. The methods involve homogenization of cells followed by differential centrifugation to provide the intracellular membranes that contain GLUT4. Subsequently, an immobilized monoclonal antibody is used for the isolation of vesicles of very high purity. The various protocols are applicable to cultured and primary adipocytes as well as skeletal muscle, the major insulin target cells expressing GLUT4.
Analyzing FAK and Pyk2 in Early Integrin Signaling Events
Authors: Bernard‐Trifilo Joie A. , Lim Ssang‐Taek , Hou Shihe , Schlaepfer David D. , Ilic Dusko
Published: April 2006

Integrins are a family of heterodimeric α/β transmembrane cell adhesion receptors that play important roles in the regulation of cell migration, proliferation, and survival. Integrins do not possess intrinsic catalytic activity, and signaling events are mediated by their lateral association with other cell surface receptors or clustering of their cytoplasmic domains with signaling proteins. Rapid activation of protein‐tyrosine kinases is one of the first signaling events associated with integrin binding to the extracellular matrix protein fibronectin. The intracellular focal adhesion kinase (FAK) is recruited to sites of integrin clustering, and this unit describes the methods with which to analyze FAK phosphorylation, activity, and localization within fibroblasts. Additional methods on how to grow primary FAK+/+ and FAK−/− fibroblasts and measure integrin‐stimulated cell motility are described as well as methods for evaluating the activity of the FAK‐related kinase, Pyk2, which is expressed in FAK−/− cells.
Anthracene
Authors: Collin Gerd , Höke Hartmut , Talbiersky Jörg
Published: April 2006

The article contains sections titled:1.Physical Properties2.Chemical Properties3.Production4.Analysis5.Uses6.Toxicology and Environmental Aspects
Spray Forming of Metals
Authors: Fritsching Udo , Bauckhage Klaus
Published: April 2006

Spray forming is an advanced process route to produce near‐net‐shaped preforms from metallic materials. As it combines the main advantages of the classical processes of metal casting and powder metallurgy, its products are characterized by extraordinary material properties. Since the 1970s this process has been developed and it is now in its commercialization state in several applications, e.g., in the automotive and aerospace industry. Though essentially a metallurgical process, understanding and optimization is based on principles of process and chemical engineering. This is reflected by means of the three process stages as: melt atomization, spray evolution, and droplet deposition. In this contribution these three subprocesses will be introduced and basic features of the process will be discussed.

The article contains sections titled:

1.Background and Potential of the Process2.Atomization3.Spraying4.Deposition5.Integral Modeling
Nanostructured Vanadium Oxide Electrodes for Enhanced Lithium‐Ion Intercalation
Authors: Wang Y. , Takahashi K. , Lee K. H. , Cao G. Z.
Published: April 2006

This article summarizes our most recent studies on improved Li+‐intercalation properties in vanadium oxides by engineering the nanostructure and interlayer structure. The intercalation capacity and rate are enhanced by almost two orders of magnitude with appropriately fabricated nanostructures. Processing methods for single‐crystal V2O5 nanorod arrays, V2O5·n H2O nanotube arrays, and Ni/V2O5·n H2O core/shell nanocable arrays are presented; the morphologies, structures, and growth mechanisms of these nanostructures are discussed. Electrochemical analysis demonstrates that the intercalation properties of all three types of nanostructure exhibit significantly enhanced storage capacity and rate performance compared to the film electrode of vanadium pentoxide. Addition of TiO2 to orthorhombic V2O5 is found to affect the crystallinity, microstructure, and possible interaction force between adjacent layers in V2O5, and subsequently leads to enhanced Li+‐intercalation properties in V2O5. The amount of water intercalated in V2O5 is found to have a significant influence on the interlayer spacing and electrochemical performance of V2O5·n H2O. A systematic electrochemical study has demonstrated that the V2O5·0.3 H2O film has the optimal water content and exhibits the best Li+‐intercalation performance.
Oto‐spondylo‐megaepiphyseal dysplasia (OSMED): Clinical and radiological findings in sibs homozygous for premature stop codon mutation in the COL11A2 gene
Authors: Temtamy Samia A. , Männikkö Minna , Abdel‐Salam Ghada M.H. , Hassan Nihal A. , Ala‐Kokko Leena , Afifi Hanan H.
Published: April 2006

Oto‐spondylo‐megaepiphyseal dysplasia (OSMED) is a very rare disorder due to mutation of type XI collagen. Less than 30 patients have been reported in the literature so far. It could be either of autosomal dominant (OMIM 154780) or recessive (OMIM 215150) etiology. Two sibs with OSMED are presented. They had disproportionate short stature and short limbs, distinct face with midface hypoplasia, short nose, depressed nasal bridge, long philtrum, and non‐progressive sensorineural deafness. Radiological findings showed short long bones and large epiphyses with metaphyseal flaring and mild platyspondyly and coronal clefting. Homozygosity of a single nucleotide deletion in exon 55 causing a premature stop codon in exon 56 of COL11A2 was detected in the affected sibs. Parents were heterozygotes for the same mutation and interestingly, the father had mild unilateral non‐progressive sensorineural deafness. This finding adds more weight that the type of mutation and location in COL11A2 are crucial in determining the phenotype. The purpose of this study is to report clinical and radiological findings in two molecularly proven Egyptian sibs with autosomal recessive OSMED. © 2006 Wiley‐Liss, Inc.
Dynamic ligand‐exchange chiral stationary phase from S‐benzyl‐(R)‐cysteine
Authors: Natalini B. , Sardella R. , Macchiarulo A. , Pellicciari R.
Published: April 2006

S‐Benzyl‐(R)‐cysteine (R‐SBC) is a new chiral ligand‐exchange stationary phase which has proved to be effective in the analytical separation of some natural and unnatural underivatized amino acids with fair to good separation and resolution factors. The dynamic coating of the RP‐18 solid support with S‐Benzyl‐(R)‐cysteine (R‐SBC) gives rise to a stable and efficient chiral stationary phase (CSP) that has been successfully employed. The mechanism of chiral recognition is discussed and a molecular modeling study aimed at identifying molecular descriptors responsible for observed different behaviours of analytes upon different albeit closely related selectors is discussed. Chirality 18:509–518, 2006. © 2006 Wiley‐Liss, Inc.
Synthesis of new enantiomerically pure macrocycles containing phenanthroline subunits
Authors: Colombo Federica , Annunziata Rita , Raimondi Laura , Benaglia Maurizio
Published: April 2006

New enantiomerically pure macrocycles have been prepared by combining 1,10‐phenanthroline 2,9‐dicarboxylic acid and two α‐amino‐acids linked through spacers. Different diamine linkers have been employed in order to modify the dimensions and the properties of the macrocycles whose structures have been studied by 1H and 13C NMR spectroscopy. The ability of the (L)‐valine containing macrocycles to bind metal ions and phenolic molecules has been investigated by 1H NMR experiments and Molecular Mechanics calculations. Chirality, 2006. © 2006 Wiley‐Liss, Inc.
Patterns and predictors of mammography utilization among breast cancer survivors
Authors: Doubeni Chyke A. , Field Terry S. , Ulcickas Yood Marianne , Rolnick Sharon J. , Quessenberry Charles P. , Fouayzi Hassan , Gurwitz Jerry H. , Wei Feifei
Published: April 2006

BACKGROUND

Improvements in cancer detection and treatment have resulted in increasing numbers of breast cancer survivors. Information regarding the use of mammography by breast cancer survivors is limited.

METHODS

The use of surveillance mammography was examined over a 5‐year period in a retrospective cohort of women age ≥ 55 years who were diagnosed with incident primary breast cancer (1996–1997) while enrolled in 1 of 4 geographically diverse integrated health systems.

RESULTS

Of the 797 women included in the study, 80% (n = 636) underwent mammograms during the first year after treatment for breast cancer. The percentage of women having mammograms during each yearly period decreased significantly over time. In multivariable analyses, older women with comorbid illnesses or those with late‐stage disease were less likely to undergo mammograms, whereas those who underwent breast‐conserving therapy (adjusted odds ratio [OR] of 1.38 [95% confidence interval (95% CI), 1.09–1.75]) were more likely to have mammograms. Women who had outpatient visits with a gynecologist (adjusted OR of 3.49 [95% CI, 2.55–4.79]), or a primary care physician (adjusted OR of 2.21 [95% CI, 1.73–2.82]) during the year were more likely to undergo mammograms in that year.

CONCLUSIONS

The use of mammography among breast cancer survivors declines over time. Efforts are needed to increase awareness among healthcare providers and breast cancer survivors of the value of follow‐up mammography. The current findings highlight the importance of maintaining ongoing contact with primary care physicians and gynecologists. Cancer 2006. © 2006 American Cancer Society.
Cholesterol oxides as biomarkers of oxidative stress in type 1 and type 2 diabetes mellitus
Authors: Ferderbar S. , Pereira E. C. , Apolinário E. , Bertolami M. C. , Faludi A. , Monte O. , Calliari L. E. , Sales J. E. , Gagliardi A. R. , Xavier H. T. , Abdalla D. S. P.
Published: April 2006

Background

Oxidative stress plays an important role in the pathophysiology of diabetes mellitus. The aim of this study was to evaluate the formation of cholesterol oxides (ChOx) as biomarkers of oxidative stress in subjects with impaired glucose tolerance (IGT) and diabetes.

Methods

Blood plasma levels of cholesterol oxidation products were determined in the following groups: type 1 diabetes mellitus (DM1), type 2 diabetes (DM2), impaired glucose tolerance (IGT), children without diabetes (C1) and adults without diabetes (C2). The serum levels of cholest‐5‐ene‐3α,7α‐diol (7α‐hydroxycholesterol, 7α‐OH), cholest‐5‐ene‐3β,7β‐diol (7β‐hydroxycholesterol, 7β‐OH), 3β‐hydroxycholest‐5‐7‐one (7‐ketocholesterol, 7‐K), 5α‐cholestane‐3β,5,6β‐triol (cholestanetriol), 5,6α‐epoxy‐5α‐cholestan‐3α‐ol (cholesterol‐5α,6α‐epoxide,), 5,6β‐epoxy‐5β‐cholestan‐3β‐ol (cholesterol‐5β,6β‐epoxide) and cholest‐5‐eno‐3β,25‐diol (25‐hydroxycholesterol, 25‐OH) (trivial name and abbreviations indicated in parentheses) were quantified by gas chromatography using flame ionization detection.

Results

The levels of total ChOx were elevated in the DM1 and DM2 groups compared to age‐matched subjects without diabetes (p< 0.05). The concentrations of 7β‐hydroxycholesterol, cholesterol‐α‐epoxide and cholesterol‐β‐epoxide were higher in the blood plasma of subjects in the DM2 group than in the blood plasma of subjects in the C2 and IGT groups (p< 0.05). Treatment of type 2 diabetic patients with oral hypoglycemic drugs associated with insulin resulted in lower concentrations of nitrotyrosine in the blood plasma without significant changes in the concentrations of glucose and glycated hemoglobin. Moreover, combination with statins in both treatments decreased the concentrations of ChOx.

Conclusions

ChOx are suitable biomarkers of oxidative stress and may be useful in clinical studies to follow drug effects on lipid oxidative modifications in diabetic patients. Copyright © 2006 John Wiley & Sons, Ltd.
Features associated with excessive exercise in women with eating disorders
Authors: Shroff Hemal , Reba Lauren , Thornton Laura M. , Tozzi Federica , Klump Kelly L. , Berrettini Wade H. , Brandt Harry , Crawford Steven , Crow Scott , Fichter Manfred M. , Goldman David , Halmi Katherine A. , Johnson Craig , Kaplan Allan S. , Keel Pamela , LaVia Maria , Mitchell James , Rotondo Alessandro , Strober Michael , Treasure Janet , Blake Woodside D. , Kaye Walter H. , Bulik Cynthia M.
Published: April 2006

Objective:

Excessive exercise and motor restlessness are observed in a substantial number of patients with eating disorders. This trait has been studied extensively among animal models of activity anorexia nervosa (AN) and may hold particular interest as an endophenotype for AN. We explored features associated with excessive exercise across subtypes of eating disorders.

Method:

Participants were female probands and affected female relatives from the multi‐site international Price Foundation Genetic Studies with diagnoses of AN, bulimia nervosa (BN), and both AN and BN or eating disorder not otherwise specified (ED‐NOS) (N = 1,857). Excessive exercise was defined based on responses to the Structured Interview for Anorexic and Bulimic Disorders (SIAB).

Results:

Among the eating disorder diagnostic groups, excessive exercise was most common among the purging subtype of AN. Individuals who reported excessive exercise also reported lower minimum BMI, younger age at interview, higher scores on anxiety, perfectionism, and eating disorder symptom measures, more obsessions and compulsions, and greater persistence.

Conclusion:

Excessive exercise may be associated particularly with the purging subtype of AN as well as with a constellation of anxious/obsessional temperament and personality characteristics among women with eating disorders. © 2006 by Wiley Periodicals, Inc. Int J Eat Disord 2006
Normal responses to specific NOD1‐activating peptidoglycan agonists in the presence of the NOD2 frameshift and other mutations in Crohn's disease
Authors: van Heel David A. , Hunt Karen A. , Ghosh Subrata , Hervé Mireille , Playford Raymond J.
Published: April 2006

Both NOD2/CARD15 alleles are mutated in ∼10% of Crohn's disease patients, causing loss of functional responses to low‐dose muropeptide agonists. We hypothesized that NOD2 mutations may also impair NOD1/CARD4 responses, supported by data suggesting NOD2 1007fs/1007fs patients had reduced responses to a putative NOD1 agonist, diaminopimelic acid‐containing muramyl tripeptide (M‐TriDAP). We measured peripheral blood mononuclear cell (n = 8 NOD2 wild type, n = 4 1007fs/1007fs, n = 6 702Trp/1007fs, n = 5 702Trp/702Trp, n = 3 908Arg/1007fs) responses to NOD1 agonists alone (IL‐8/TNF‐α), and agonist enhancement of lipopolysaccharide (LPS) responses (IL‐1β). Significant responses were seen with M‐TriDAP at 10 nM (as with NOD2 agonists), but only at ⩾100 nM with FK565/TriDAP. M‐TriDAP induced IL‐8/TNF‐α secretion, and enhancement of LPS IL‐1β responses was significantly reduced between NOD2 double mutation carriers versus healthy controls, whereas there was no difference with FK565 or TriDAP stimulation, or between 1007fs/1007fs cells and other genotypes. M‐TriDAP contains both NOD1 (γ‐D‐Glu‐mesoDAP) and NOD2 (MurNAc‐L‐Ala‐D‐Glu) minimal structures whereas FK565/TriDAP contain only NOD1 activating structures. M‐TriDAP has dual NOD1/NOD2 agonist activity in primary cells, possibly due to different intracellular peptidoglycan processing compared to the HEK293 cell system typically used for agonist specificity studies. Responses to specific NOD1 agonists are unaffected by NOD2 genotype, suggesting independent action of the NOD1 and NOD2 pathways.
Recent applications of capillary electrophoresis‐electrospray ionisation‐mass spectrometry in drug analysis
Authors: Smyth W. Franklin
Published: April 2006

This review considers applications in 2004–2005 of capillary electrophoresis‐electrospray ionisation‐mass spectrometry (CE‐ESI‐MS) to the detection and determination of small molecular mass drug molecules, taken from the Web of Knowledge database. The molecules of small molecular mass less than 1000 Da are chosen according to selected structural classes in which they give ESI signals primarily as [M+H]+ ions. These structural classes are drugs with amine‐containing side chains, drugs with N‐containing saturated ring structures, 1,4‐benzodiazepines, other heterocyclic hypnotics, steroids, bioactive compounds containing phenolic groups, and miscellaneous molecules. Details are given on the fragmentations, where available, that these ionic species exhibit in‐source and in ion‐trap, triple quadrupole and time‐of flight mass spectrometers. The review then gives a critical evaluation of these recent CE‐ESI‐MS analytical methods for the detection and determination of these small molecular mass drug molecules. Analytical information on, for example, sample concentration techniques, CE separation conditions, recoveries from biological media and limits of detection are provided.
Conservation laryngeal surgery versus total laryngectomy for radiation failure in laryngeal cancer
Authors: Holsinger F. Christopher , Funk Etai , Roberts Dianna B. , Diaz Eduardo M.
Published: April 2006

Background.

Total laryngectomy is the standard of care for surgical salvage of radiation failure in laryngeal cancer. However, the role of conservation laryngeal surgery in this setting remains unclear. The objective was to compare the efficacy of conservation versus total laryngectomy for salvage of radiation failure in patients who initially presented with T1 or T2 squamous cancer of the larynx.

Methods.

A 21‐year retrospective analysis of patients who received surgery at a single comprehensive cancer center after definitive radiation therapy is reported. At recurrence, the patients were reevaluated and then underwent a total laryngectomy or, if possible, a conservation laryngeal procedure. The charts of 105 patients who failed radiation treatment for primary laryngeal cancer and who subsequently underwent surgical salvage were reviewed for this study. Eighty‐nine were male (84.8%). The mean age was 60.3 years. The median follow‐up time after surgery was 69.4 months. Most patients with recurrence after radiotherapy required total laryngectomy (69.5%; 73/105). Conservation laryngeal surgery was performed for 32 patients (31.5%). Concomitant neck dissections were performed on 45 patients (45.5%).

Results.

In 14 patients, local or regional recurrence developed after salvage surgery: 9 patients after total laryngectomy (12.3%; 9/73), and 5 patients (15.6%; 5/32) after conservation laryngeal surgery. This difference was not statistically significant, nor was there a difference in disease‐free interval for the two procedures (p = .634, by log‐rank test). Distant metastasis developed in 13 patients. Most developed in the setting of local and/or regional recurrence, but distant metastasis occurred as the only site of failure in 6 of the patients who had undergone total laryngectomy but in 1 of the conservation surgery patients treated for a supraglottic laryngeal cancer. The overall mortality for patients who underwent total laryngectomy was also higher: 73.74% (54/73) versus 59.4% (19/32) for patients who underwent a conservation approach (p = .011 by log‐rank test).

Conclusions.

Although conservation laryngeal surgery was possible in a few patients with local failure after radiotherapy, conservation laryngeal surgery is an oncologically sound alternative to total laryngectomy for these patients. © 2006 Wiley Periodicals, Inc. Head Neck, 2006
Use of multi‐platform, multi‐temporal remote‐sensing data for calibration of a distributed hydrological model: an application in the Arno basin, Italy
Authors: Campo Lorenzo , Caparrini Francesca , Castelli Fabio
Published: April 2006

Images from satellite platforms are a valid aid in order to obtain distributed information about hydrological surface states and parameters needed in calibration and validation of the water balance and flood forecasting. Remotely sensed data are easily available on large areas and with a frequency compatible with land cover changes. In this paper, remotely sensed images from different types of sensor have been utilized as a support to the calibration of the distributed hydrological model MOBIDIC, currently used in the experimental system of flood forecasting of the Arno River Basin Authority. Six radar images from ERS‐2 synthetic aperture radar (SAR) sensors (three for summer 2002 and three for spring–summer 2003) have been utilized and a relationship between soil saturation indexes and backscatter coefficient from SAR images has been investigated. Analysis has been performed only on pixels with meagre or no vegetation cover, in order to legitimize the assumption that water content of the soil is the main variable that influences the backscatter coefficient. Such pixels have been obtained by considering vegetation indexes (NDVI) and land cover maps produced by optical sensors (Landsat‐ETM). In order to calibrate the soil moisture model based on information provided by SAR images, an optimization algorithm has been utilized to minimize the regression error between saturation indexes from model and SAR data and error between measured and modelled discharge flows. Utilizing this procedure, model parameters that rule soil moisture fluxes have been calibrated, obtaining not only a good match with remotely sensed data, but also an enhancement of model performance in flow prediction with respect to a previous calibration with river discharge data only. Copyright © 2006 John Wiley & Sons, Ltd.
Hydrological processes controlling ground and surface water flow from a hypermaritime forest–peatland complex, Diana Lake Provincial Park, British Columbia, Canada
Authors: Emili Lisa A. , Price Jonathan S.
Published: April 2006

The proposed harvesting of previously undeveloped forests in north coastal British Columbia requires an understanding of hydrological responses. Hydrometric and isotopic techniques were used to examine the hydrological linkages between meteoric inputs to the surface‐groundwater system and runoff response patterns of a forest‐peatland complex. Quickflow accounted for 72–91% of peak storm discharge. The runoff ratio was lowest for open peatland areas with thick organic horizons (0·02–0·05) due to low topographic gradients and many surface depressions capable of retaining surface water. Runoff ratio increased comparatively for ephemeral surface seep flows (0·06–0·40) and was greatest in steeply sloping forest communities with more permeable soils (0·33–0·69). The dominant mechanism for runoff generation was saturated shallow subsurface flow. Groundwater fluxes from the organic horizon of seeps (1·70–1·72 m3 day−1 m−1) were an important component of quickflow. The homogeneous δ2Hδ18O composition of groundwater indicated attenuation of the seasonal rainfall signal by mixing during recharge. The positive correlation (r2 = 0·64 and 0·38, α = 0·05) between slope index and δ18O values in groundwater suggests that the spatial pattern in the δ18O composition along the forest‐peatland complex is influenced by topography and provides evidence that topographic indices may be used to predict groundwater residence time. Copyright © 2006 John Wiley & Sons, Ltd.
A process‐based transfer function approach to model tile‐drain hydrographs
Authors: Arabi Mazdak , Stillman Jennifer S. , Govindaraju Rao S.
Published: April 2006

Tile‐drain response to rainfall events is determined by unsaturated vertical flow to the water table, followed by horizontal saturated water movement. In this study, unsaturated vertical movement from the redistribution of water is modelled using a sharp‐front approximation, and the saturated horizontal flow is modelled by an approximate solution to the Boussinesq equation. The unsaturated flow component models the fast response that is associated with the presence of preferential flow paths. By convoluting the responses of the two components, a transfer function is developed that predicts tile‐drain response to unit amounts of infiltrated water. It is observed that the unsaturated flow component can be cast in a form that is linear in a power function of the infiltrated depth. Since the approach is process based, model parameter definitions are easily identified with soil properties at the field scale. Furthermore, it is demonstrated that the transfer function model parameters can be estimated from moment analysis. Using superposition, the transient tile‐drain response to arbitrary amounts of infiltrated water can be constructed. Comparison with data measured from the Water Quality Field Station show that this approach provides a promising method for generating tile‐drain response to rainfall events. Copyright © 2006 John Wiley & Sons, Ltd.