bluuebunny/crossref_metadata_2025 huggingface dataset:
Sojourn times with finite time‐horizon in finite semi‐markov processes
Authors: Csenki Attila
Published: May 2007

Let Y = {Yt:t ≥ 0} be a semi‐Markov process with finite state space S. Assume that Y is either irreducible and S is then partitioned into two classes A and B, or, that Y is absorbing and S is partitioned into A, B and C, where C is the set of all absorbing states of Y. Denote by TA, m(t) the mth sojourn time of Y in A during [0, t]. TA, m(t) is thus defined as the duration in [0, t] of the mth visit of Y to A if A is visited by Y during [0, t] at least m times; TA, m(t) = 0 otherwise. We derive a recurrence relation for the vectors of double Laplace transforms gm**(T1,T2) = {gm**(T1, T2;S):sSC}, m = 1,2,… which are defined by

with T1, T2, Re(T1), Re(T2) > 0. This result is then applied to alternating renewal processes. Symbolic Laplace transform inversion with MAPLE is used to obtain the first two moments of TA, m(t). The assumed holding time distributions are exponential and Erlang respectively. This paper is a continuation of some of the author's recent work on the distribution theory of sojourn times in a subset of the finite state space of a (semi‐)Markov process where the time horizon t = + ∞. The practical importance of considering a finite time horizon for semi‐Markov reliability models has been discussed recently by Jack (1991), Jack and Dagpunar (1992), and Christer and Jack (1991).
On the limiting joint distribution of the extreme order statistics
Authors: Scarf P. A.
Published: May 2007

The connection between extreme values and record‐low values is exploited to derive simply the limiting joint distribution of the r largest order statistics. The use of this distribution in the modelling of corrosion phenomena is considered, and the extrapolation of maxima in space and time is described in this context. There has been recent emphasis on movement away from classical extreme value theory to more efficient estimation procedures. This shift is continued with the illustration of the extra precision of predicted maxima obtained from a model based on extreme order statistics over the classical extreme value approach.
A stochastic system with MMPP input and an access function
Authors: Tralhão Lino , Craveirinha José , Paixão José
Published: May 2007

In classical studies of loss systems with restricted availability, the utilization was suggested of a probabilistic loss function, defining the conditional probability of an incoming call being rejected, as a function of the number of occupations in the destination group of servers. This paper gives an exact analysis of stochastic processes of practical relevance, associated with a system with MMPP (Markov Modulated Poisson Process) input, finite queueing capacity and a general loss function, assuming exponential service times. In addition to the process defining the state of the system at any instant, the analysis of the overflow point process (associated with the rejected arriving customers), the accepted point process (associated with the accepted arriving customers), and of the departure process will be presented. Together with the exact analysis of this system, based on the matrix analytical methodology of Neuts, (1981), we will derive expressions for calculating some key‐parameters of pertinent associated processes, which may also be used for their approximate modelling. Also, examples of applications and of blocking probability calculations in specific models of this class will be presented.
Monitoring a class of discrete point processes
Authors: Chandramouli Y.
Published: May 2007

A discrete, non‐negative integer‐valued, stationary point process was proposed by Neuts and Pearce as a model for teletraffic packet streams. We examine a data‐analytic approach to develop a monitoring scheme for that point process. Monitoring is a procedure of tracking a stochastic process to identity quickly the development of anomalous situations in the evolution of the point process and to detect the assignable causes to account for such conditions. Numerical results are presented to illustrate the performance of the monitoring scheme.
Discovering interesting statements from a database
Authors: Gebhardt F.
Published: May 2007

Knowledge discovery aims at extracting new knowledge from potentially large databases; this may be in the form of interesting statements about the data. Two interrelated classes of problem arise that are treated here: to put the subjective notion of ‘interesting’ into concrete terms and to deal with large numbers of statements that are related to one another (one rendering the other redundant or at least less interesting). Four increasingly subjective facets of ‘interestingness’ are identified: the subject field under consideration, the conspicuousness of a finding, its novelty, and its deviation from prior knowledge. A procedure is proposed, and tried out on two quite different data sets, that allows for specifying interestingness by various means and that ranks the results in a way that takes interestingness (relevance, evidence) as well as mutual relatedness (similarity, affinity) into account—manifestations of the second and third facets of interestingness in the given data environment.
Nested sampling for estimating spatial semivariograms compared to other designs
Authors: Corsten L. C. A. , Stein A.
Published: May 2007

In spatial studies, use is commonly made of nested sampling plans. By applying such plans, one takes observations according to a hierarchical scheme, with decreasing distances between observations. As observed by Miesch (1975), the cumulative sum of variance components provided by the nested sampling plan may be used in some situations to obtain semivariogram values. In this article, proofs are given for both balanced and unbalanced designs. Different estimation procedures for obtaining semivariogram values are compared with each other. The paper is illustrated with two numerical examples, one on actual soil pH data and one on simulated random fields. Mean squared pair differences are shown to be inferior to expected mean squares and restricted maximum likelihood for variance component estimation and several other spatial sampling plans may be superior to the nested sampling plan for estimating the spatial semivariogram.
Reliability analysis of repairable systems from in–service failure count data
Authors: Calabria R. , Guida M. , Pulcini G.
Published: May 2007

Point maximum likelihood estimators for parameters, mean number of failures, and failure rate in a non–homogeneous Poisson process are derived, when only count data from k identical processes are available. Approximate confidence intervals based on the parametric bootstrap technique are considered. The performances of both the point and interval estimation procedures are assessed via Monte Carlo simulation.
Alternative optimality criteria of portfolio selection based upon threshold stopping rule
Authors: Dohi Tadashi , Kitaoka Eiichi , Osaki Shunji
Published: May 2007

This paper proposes two types of alternative criteria of optimality for the continuous time portfolio selection problem. The optimality criteria, the so–called Laplace–Stieltjes transform (LST) criteria, are based on the assumption that the financial agent has a target level for the wealth accumulation process. These criteria are closely related to the so–called threshold stopping investment rule. We analytically derive the LST criteria and numerically compare them with the well–known Kelly criterion. It is shown that the portfolio strategies suggested may overcome the problem that the growth portfolio is often overestimated in several investment situations.
Acceptance sampling in a producer—supplier conflicting environment: Risk neutral case
Authors: Tapiero Charles S.
Published: May 2007

This paper considers a mutual inspection game which follows the signing of a quality delivery contract. The basic strategic decisions considered involve both the supplier and producer acceptance sampling procedure on the same lot. To solve the game, we consider the classical notions of ‘producer’ and ‘consumer’ risks and define a random payoffs game. To simplify our analysis, we assume risk neutrality by both the producer and the supplier. The approach of this paper provides a departure point from traditional acceptance sampling, to an approach which recognizes explicit motivations and the pursuit of self‐interest as well as the cost of information for the parties involved. As a result, the traditional formulation of sampling plans, designed in terms of risk considerations based on Neyman—Pearson theory in hypothesis testing, is deemed limited. For demonstration purposes, an example is solved.
Estimating the instantaneous volatility and covariance of risky assets
Authors: Chesney Marc , Elliott Robert J.
Published: May 2007

Using the Mihlstein approximation for solutions to stochastic differential equations and the stochastic calculus an estimate for the volatility is obtained. The estimate is also valid for stochastic, Markov, volatilities. If the process has jumps, these reduce the previous estimate. The instantaneous covariance of two risky assets is also calculated.
Analytic solution and estimation of parameters on a stochastic exponential model for a technological diffusion process
Authors: Katsamaki A. , Skiadas C. H.
Published: May 2007

In this paper we examine the behaviour of a stochastic model that describes a technological diffusion process (continuously increasing process). Furthermore we obtain a solution for the proposed model through the estimation of the volatility using three different approximations. The adjustment of real data to the final stochastic model confirms its ability of describing and forecasting real cases.
Multiattribute evaluation of greek banking performance
Authors: Zopounidis C. , Despotis D. K. , Stavropoulou E.
Published: May 2007

Ordinal regression analysis is proposed as a means for evaluating banking performance over multiple attributes in the presence of non‐monotonic preferences. First, a multivariate statistical analysis is applied to measure the banking performance on the basis of financial ratios that derive from the study of financial statements of a sample of Greek banks for the period 1989–1992. Then, an additive utility model is assessed to obtain the final ranking of a representative sample of Greek banks.
Daniels's association measures under right censoring
Authors: O'Quigley John
Published: May 2007

This paper considers extensions of the Daniels generalized measures of association (Daniels 1944) to censored data. A number of existing tests for the detection of association in the presence of right‐censoring (Gehan 1965; Efron 1967; Brown, Hollander and Korwar 1974; Weier and Basu 1980) are seen to be special cases of the Daniels coefficient under particular scoring schemes. The Daniels coefficient provides a very general framework for the construction of tests and a number of other scoring schemes, simplifying to give well known tests in the non‐censored case, are considered. In this paper we focus attention on tests which are, in some sense, non‐parametric with respect to both variables, i.e. the explanatory variable as well as the failure time variable, such a property, though, not necessarily implying rank invariance. Parametric tests can be seen to fit in with the same formulation although no exploration of this approach is given here. Moving away from the null hypothesis of no association, it is also possible to obtain population measures of association applicable to right censored data. These will not in general converge to their non‐censored equivalents although, for a large family of cases studied, they do come very close. We illustrate these findings by some simulations.
Estimating a survival function with doubly censored data in a proportional hazard model
Authors: Esteban M. D. , Morales D.
Published: May 2007

This article presents a non‐parametric estimator of a survival function in a proportional hazard model when some of the data are censored on the left and some are censored on the right. The proposed method generalizes the work of Ebrahimi (1985). Uniformly strong consistency and asymptotic normality of the estimator are proved. A computer simulation study is presented to analyse the behaviour of the estimator when model assumptions fit the data and when they do not fit.
A discrete‐time model of failure and repair
Authors: Rocha‐Martinez José M. , Shaked Moshe
Published: May 2007

In this paper the authors introduce and study a model of failures and repairs of units with discrete lifetimes. They suppose that a unit has a sequence of tasks to perform and that its lifetime is measured by the number of tasks performed before its final, fatal failure. Upon a failure the unit may be repaired (with some probability) and then it may attempt again to perform the current task. The unit dies when (with some probability) a repair cannot be completed. We derive some stochastic comparisons of pairs of such models. The stochastic comparisons are then applied for obtaining results regarding the inheritance of several aging properties by the repaired unit. Various examples illustrate the applicability of the model. Some variants of the model of this paper can be viewed as discrete analogues of the notion of imperfect repair.
Computational approaches to estimation in the principal component analysis of a stochastic process
Authors: Aguilera Ana M. , Gutiérrez Ramón , Ocaña Francisco A. , Valderrama Mariano J.
Published: May 2007

After performing a review of the classical procedures for estimation in the principal component analysis (PCA) of a second order stochastic process, two alternative procedures have been developed to approach such estimates. The first is based on the orthogonal projection method and uses cubic interpolating splines when the data are discrete. The second is based on the trapezoidal method. The accuracy of both procedures is tested by simulating approximated sample‐functions of the Brownian motion and the Brownian bridge. The real principal factors of these stochastic processes, which can be evaluated directly, are compared with those estimated by means of the two mentioned algorithms. An application for estimation in the PCA of tourism evolution in Spain from real data is also included.
Allfinanz, bancassurance and the future of banking
Authors: Bergendahl GÖRan
Published: May 2007

The purpose with this paper is first to analyse the strategies of Allfinanz (Bancassurance) in Germany and then to investigate if the German banks have become more efficient during the period since Allfinanz was introduced. Two methods are used to analyse efficiency: ‘financial ratio analysis’ (FRA) and ‘data envelopment analysis’ (DEA). FRA is useful in studying the change in productivity. DEA generates, efficiency scores and alternative and more efficient combinations of banks.
Nanofibers of Fullerene C60 through Interplay of Ball‐and‐Socket Supermolecules
Authors: Hubble Lee J. , Raston Colin L.
Published: May 2007

Mixing solutions of p‐tBu‐calix[5]arene and C60 in toluene results in a 1:1 complex (C60)∩(p‐tBu‐calix[5]arene), which precipitates as nanofibers. The principle structural unit is based on a host–guest ball‐and‐socket nanostructure of the two components, with an extended structure comprising zigzag/helical arrays of fullerenes (powder X‐ray diffraction data coupled with molecular modeling). Under argon at temperatures above 309 °C, the fibers undergo selective volatilization of the calixarenes to afford C60‐core nanostructures encapsulated in a graphitic material sheath, which exhibits a dramatic increase in surface area. Above 650 °C the material exhibits an ohmic conductance response, due to the encapsulation process.
Berufsbildung für produktionsbetreuende Berufe in der chemischen Industrie: Auf völlig neuen Wegen ins nächste Jahrtausend
Authors: Schmidkunz Heinz , Kubik Günther
Published: May 2007

DIE BERUFLICHE AUSBILDUNG erfolgt in Deutschland in Berufsfeldern. Bei der Betreuung von Großanlagen in der chemischen Industrie müssen drei Fachkräfte aus drei Berufsgruppen zusammenarbeiten. Erfahrungsgemäß treten dabei Schwierigkeiten bei der Kommunikation und der erforderlichen Zusammenarbeit auf. Der daraus resultierende Schaden kann beachtlich sein. Um diesen Mißständen abzuhelfen, wurde ein Modellversuch eingerichtet. Auszubildende in den drei betreffenden Berufen (Chemikanten, Industriemechaniker und Prozeßleitelektroniker) wurden zeitweise berufsfeldübergreifend ausgebildet. Die Ergebnisse der Untersuchung werden eingehend erörtert, Konsequenzen werden angedeutet.
Die Bestimmung des Zinnionen‐Gehalts in Ananaskonserven
Authors: Stübs Renate , Heldt Nina
Published: May 2007

QUANTITATIVE ANALYSEN haben im Chemieunterricht der gymnasialen Oberstufe dann eine besondere Wirkung und entwickeln beim Schüler eine nachhaltige Motivation, wenn sie nicht nur Selbstzweck an dafür eigens hergestellten Lösungen sind, sondern wenn damit auch weitergehende Kenntnisse über chemische Aspekte der Lebenswelt gewonnen werden können. Das ist bei der komplexometrischen Bestimmung von Zinnionen in Ananaskonserven der Fall. Der Ratschlag, den Inhalt geöffneter, innen mit Zinn beschichteter Weißblechdosen sofort in Gefäße aus Porzellan oder Glas umzuschütten, erfährt durch die selbst gewonnenen Analysenergebnisse eine einleuchtende Begründung. Die Frage nach der Ursache des schnell steigenden Zinnionen‐Gehalts nach dem Öffnen der Dose findet eine Erklärung in der Sauerstoffkorrosion der Metalle. Das bedeutet, daß anspruchsvolle analytische Aufgaben nicht nur mit Aspekten der Lebenswelt, sondern auch mit einem wichtigen anderen chemischen Gebiet, der Elektrochemie, verknüpft werden können.
Hyperglycemia in patients with acute myeloid leukemia is associated with increased hospital mortality
Authors: Ali Naeem A. , O'Brien James M. , Blum William , Byrd John C. , Klisovic Rebecca B. , Marcucci Guido , Phillips Gary , Marsh Clay B. , Lemeshow Stanley , Grever Michael R.
Published: May 2007

BACKGROUND.

Hyperglycemia is often observed in medically ill patients. Previous studies have shown that patients with hyperglycemia during induction therapy for acute lymphoblastic leukemia develop more infections and have shorter disease‐free survival. The authors hypothesized that hyperglycemia may be associated with adverse outcomes in patients with acute myeloid leukemia (AML) and sought to determine whether this association exists in this population.

METHODS.

The authors performed a retrospective cohort study to examine the relation between hyperglycemia and hospital mortality in patients with the diagnosis of AML. Two hundred eighty‐three adult patients were treated over a 3‐year period. All hospitalizations were reviewed during the study period, and glucose exposure and outcomes were quantified.

RESULTS.

Hyperglycemia during a patient's hospitalization was associated with increased hospital mortality (OR, 1.38; 95% CI, 1.23–1.55; P < .001) after adjusting for covariates, including disease state, treatment type, and response. The rise in mortality was evident at even mild levels (110–150 mg/dL) of glucose elevation. Although the odds of developing severe sepsis (OR, 1.24; 95% CI, 1.13.–1.38; P < .001) or severe sepsis with respiratory failure (OR, 2.04; 95% CI, 1.44–2.91; P < .001) were increased with hyperglycemia, sepsis did not appear to be the main factor responsible for the negative impact of hyperglycemia on hospital mortality.

CONCLUSIONS.

This study demonstrated an association between hospital mortality and even modest levels of hyperglycemia in AML patients. Prospective studies are needed to confirm this association and to discern causal pathways that mediate this effect. Cancer 2007. © 2007 American Cancer Society.
Fabrication of Hexaphenylsilole Nanowires and Their Morphology‐Tunable Photoluminescence
Authors: Heng Liping , Zhai Jin , Qin Anjun , Zhang Yuqi , Dong Yongqiang , Tang Ben Zhong , Jiang Lei
Published: May 2007

Immersion of nanoporous alumina membranes into saturated solutions of hexaphenylsilole with subsequent solvent evaporation affords aligned organic nanowires. The luminescent properties of the hexaphenylsilole nanowires can be manipulated by varying their morphologies, which were controlled by changing the channel sizes of the alumina templates.
Single‐Molecule Studies of a Model Fluorenone
Authors: Odoi Michael Y. , Hammer Nathan I. , Rathnayake Hemali P. , Lahti Paul M. , Barnes Michael D.
Published: May 2007

Single‐molecule fluorescence measurements of 2,7‐bis(3,4,5‐trimethoxyphenylethenyl)fluorenone (OFOPV) reveal narrow emission spectra concentrated around 540 nm, with weak emission at longer wavelengths. The wide scattering of emission‐maximum wavelengths is attributed to varying molecular environments, with dimers or higher‐order aggregates contributing to the low‐energy emission. This spectral distribution indicates that emission from monomers of this model fluorenone is mostly green, which is consistent with contaminant emission (g‐bands) often observed in fluorene‐ and polyfluorene‐based organic light emitting diode (OLED) devices. A histogram of center wavelengths from 118 single‐molecule spectra shows good agreement with the green emission previously observed in thermally stressed 2,7‐bis(3,4,5‐trimethoxyphenylethenyl)‐9,9‐diethylfluorene (OFPV). Whereas bulk OFPV exhibits blue fluorescence at about 480 nm, OFOPV bulk thin film measurements reveal red luminescence shifted to 630 nm. This unexpected peak position for bulk OFOPV shifts to higher energies (ca. 540 nm) upon dilution in a solid‐state matrix, suggesting that the bulk red emission finds its origins in interactions between fluorenone molecules. Explanations for this red emission include aggregate or excimer formation or intermolecular energy transfer between fluorenone molecules.
Noise removal for degraded images with Poisson noise using M‐transformation and BayesShrink method
Authors: Li Yeqiu , Lu Jianming , Wang Ling , Yahagi Takashi
Published: May 2007

Median filters and other nonlinear filters have been investigated for restoration of degraded images with Poisson noise. Recently, subband image restoration using the wavelet transform has been attracting much attention. This method is effective for small‐amplitude noise, but in the case of Poisson noise, large‐amplitude noise exceeds the preset threshold and is not removed. In this study, we propose a new method of noise removal from degraded images with Poisson noise by using a combination of the M‐transformation [5] and the wavelet BayesShrink method. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(11): 11–20, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20357
Antigen presentation and transfer between B cells and macrophages
Authors: Harvey Bohdan P. , Gee Renelle J. , Haberman Ann M. , Shlomchik Mark J. , Mamula Mark J.
Published: May 2007

B cells play an active role in directing immunity against specific proteins in part because of their capacity to sequester antigen via B cell receptor (BCR). Our prior findings indicate that B cells can initiate an immune response in vivo to self proteins independent of other antigen‐presenting cells (APC). However, these studies also demonstrated that both dendritic cells and macrophages are important in the ongoing immune response. The present work illustrates a mechanism by which antigen acquired by B cells through BCR is specifically transferred to other APC, in particular, macrophages. The transfer of antigen is dependent on the specificity of BCR and requires direct contact between the cells, but does not require MHC compatibility between the cells and is independent of the activation state of macrophages. Antigen transfer is functional, in that macrophages, which received B cell derived‐antigen, can activate CD4 T cells. Overall, these results define a novel mechanism by which B cells can focus immunity toward a specific antigen and transfer the ability to activate CD4 T cells to other APC.
Alternative Synthesis, Density Functional Calculations and Proton Reactivity Study of a Trinuclear [NiFe] Hydrogenase Model Compound
Authors: Lauderbach Frank , Prakash Raju , Götz Andreas W. , Munoz Marcela , Heinemann Frank W. , Nickel Ulrich , Hess Bernd A. , Sellmann Dieter
Published: May 2007

The trinuclear complex [(‘S2’){Ni(PMe3)}2Fe(CO)(‘S2’)2] (1) {‘S2’2– = 1,2‐benzenedithiolate(2–)} has been reported as a structural as well as functional model for [NiFe] hydrogenases since it contains key structural features of the [NiFe] hydrogenase active site, and is oxidized by protons to give [1]+ and H2. Complex 1 formed as an unexpected product from the reaction of [Fe(CO)2(‘S3’)]2 {‘S3’2– = bis(2‐mercaptophenyl) sulfide(2–)} and [Ni(PMe3)2(‘S2’)]. Both the iron and nickel centers of 1 are chelated by ‘S2’ donors, but not with any ‘S3’ ligand. In order to understand this reaction, the new precursor [Fe(CO)2(siS3)]2 (2) {siS32– = bis(2‐mercapto‐3‐trimethylsilylphenyl) sulfide(2–)} was synthesized. Compound 2 readily loses its CO ligand to give [Fe(CO)(siS3)]2 (3), which consists of two 16 valence electron fragments and could be isolated in the solid state. Conversion of 3 to 2 is feasible with gentle bubbling of CO gas for about 2 min. Treatment of 2 with [Ni(PMe3)2(‘S2’)] resulted exclusively in the formation of complex 1, which confirms that all three ‘S2’ ligands in 1 originate from [Ni(PMe3)2(‘S2’)]. Therefore, an alternative synthesis of 1, which does not involve any ‘S3’ ligand, has been developed. Density functional theory (DFT) calculations suggest that the oxidation states of the metal centers are FeII and NiII and do not change upon oxidation of 1 to [1]+. The unpaired electron in [1]+ is located to a large extent on the nickel atoms and the adjacent thiolate donor functions. The charge, however, is distributed over the whole cluster, main parts residing on the ‘S2’ ligands. Preliminary constant potential coulometric measurements indicate that 1 mediates the reduction of protons to dihydrogen at a mild potential (–0.48 V vs. NHE). Based upon these experimental and theoretical results, plausible mechanisms for this reduction are briefly discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
The Role of Escherichia coliform in the Biomineralization of Calcium Oxalate Crystals
Authors: Chen Long , Shen Yuhua , Jia Rong , Xie Anjian , Huang Bei , Cheng Xiaobin , Zhang Qingfeng , Guo Ruiyong
Published: May 2007

The influence of the common bacterium Escherichia coliform (E. coli) on the nucleation and growth of calcium oxalate (CaOxa) in aqueous solution is studied in order to determine its role in the biomineralization of urinary stones. The results show that CaOxa crystals obtained in the presence of E. coli transform more quickly from calcium oxalate dihydrate (COD) into calcium oxalate monohydrate (COM), and they become even larger, than in the absence of the bacterium. On decreasing the concentration of chemical reagents, in other words increasing the ratio bacterium/CaOxa, except for the more rapid phase transition from COD to COM, the CaOxa particles obtained become larger and more regular with a hexagonal morphology. This suggests that E. coli accelerates the crystallization of COM, which is the most stable crystal phase of CaOxa and the major component of urinary stones. Transmission electron microscopy (TEM) images, electron diffraction (ED) patterns, and Fourier‐transform IR (FTIR) spectra show that the biomineralization process of CaOxa crystals takes place both inside and outside the bacterium, which implies that it is induced by both intracellular biomolecules and the bioorganic secretions of the bacteria. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) data and UV/Vis spectra show that the proteins bound to the crystal surface with a molecular weight of around 26.5 kDa have tyrosine, tryptophan, or phenylalanine residues. The zeta potential and FTIR spectra are used to investigate the mineralization mechanism of CaOxa with E. coli and show that, the negatively charged biomolecules inside and outside the bacterium interact with Ca2+ ions to provide nucleation sites and then act as modifiers to induce the nucleation, growth, and aggregation of COM crystals. Therefore, we infer that E. coli mineralizes calcium oxalate and plays a role in the formation of urinary stones.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Hypomethylation of PRAME is responsible for its aberrant overexpression in human malignancies
Authors: Schenk Tino , Stengel Sven , Goellner Stefanie , Steinbach Daniel , Saluz Hans Peter
Published: May 2007

The preferentially expressed antigen of melanoma (PRAME) is expressed at high levels in large fractions of human malignancies, e.g., acute myeloid leukemia. Therefore, PRAME is an important marker for diagnosis of various malignant diseases and a relevant parameter for monitoring minimal residual disease. It is supposed to be involved in tumorigenic processes. Because of these important aspects we investigated its transcriptional regulation in detail. Most relevant was a detailed DNA methylation analysis of the PRAME 5′ region by genomic sequencing in correlation with PRAME expression in various human patient samples and cell lines. In combination with DNA‐truncation/transfection experiments with respect to DNA methylation, we show that changes in the methylation pattern in defined parts of the regulatory regions of PRAME are sufficient for its upregulation in cells usually not expressing the gene. © 2007 Wiley‐Liss, Inc.
Water uptake by trees in a riparian hardwood forest (Rhine floodplain, France)
Authors: Sánchez‐Pérez José Miguel , Lucot Eric , Bariac Thierry , Trémolières Michèle
Published: May 2007

Water flow in the soil–root–stem system was studied in a flooded riparian hardwood forest in the upper Rhine floodplain. The study was undertaken to identify the vertical distribution of water uptake by trees in a system where the groundwater is at a depth of less than 1 m. The three dominant ligneous species (Quercus robur, Fraxinus excelsior and Populus alba) were investigated for root structure (vertical extension of root systems), leaf and soil water potential (Ψm), isotopic signal (18O) of soil water and xylem sap. The root density of oak and poplar was maximal at a depth of 20 to 60 cm, whereas the roots of the ash explored the surface horizon between 0 and 30 cm, which suggests a complementary tree root distribution in the hardwood forest. The flow density of oak and poplar was much lower than that of the ash. However, in the three cases the depth of soil explored by the roots reached 1·2 m, i.e. just above a bed of gravel. The oak roots had a large lateral distribution up to a distance of 15 m from the trunk. The water potential of the soil measured at 1 m from the trunk showed a zone of strong water potential between 20 and 60 cm deep. The vertical profile of soil water content varied from 0·40 to 0·50 cm3 cm−3 close to the water table, and 0·20 to 0·30 cm3 cm−3 in the rooting zone. The isotopic signal of stem water was constant over the whole 24‐h cycle, which suggested that the uptake of water by trees occurred at a relatively constant depth. By comparing the isotopic composition of water between soil and plant, it was concluded that the water uptake occurred at a depth of 20 to 60 cm, which was in good agreement with the root and soil water potential distributions. The riparian forest therefore did not take water directly from the water table but from the unsaturated zone through the effect of capillarity. Copyright © 2007 John Wiley & Sons, Ltd.
Neuronal protein synuclein γ predicts poor clinical outcome in breast cancer
Authors: Guo Jianping , Shou Chengchao , Meng Lin , Jiang Beihai , Dong Bin , Yao Lihua , Xie Yuntao , Zhang Jianzhi , Chen Yiding , Budman Daniel R. , Shi Yuenian Eric
Published: May 2007

Synuclein γ (SNCG), previously identified as a breast cancer‐specific gene (BCSG1), is highly expressed in breast carcinomas but not in normal epithelium. SNCG regulates many pathways in growth and progression of breast cancer. To determine if SNCG is a biomarker for clinical prognosis of breast cancer, we generated a panel of murine monoclonal antibodies (mAbs) against human SNCG and correlated SNCG protein expression in 358 clinical breast cancer specimens with clinical outcome. A panel of 14 mAbs was characterized by ELISA, immunoprecipitation (IP), Western blot, immunocytochemistry and immunohistochemistry. SNCG protein expression was determined in 438 clinical breast specimens by immunohistochemical analysis using mAb 5C5. Expression of SNCG was strongly correlated with the stage, lymph node involvement, metastasis, tumor size and Her‐2 status, but its expression was not associated with ER and PR expression status. While 71.4% of advanced breast cancers were positive for SNCG expression, only 26.8% of Stage I/II breast cancers were positive for SNCG expression and 5.2% of benign hyperplasia expressed SNCG. SNCG protein was not detectable in normal tissue adjacent to breast cancer. After a median follow‐up of 64 months, patients with an SNCG‐positive tumor had a significantly shorter disease‐free survival and overall survival and a high probability of death compared no expression of SNCG. Multivariate analysis demonstrated that SNCG was a strong independent prognostic variable. SNCG is a new unfavorable prognostic marker for breast cancer progression and a potential target for breast cancer treatment. © 2007 Wiley‐Liss, Inc.
Inhibition of Wnt‐2 and galectin‐3 synergistically destabilizes β‐catenin and induces apoptosis in human colorectal cancer cells
Authors: Shi Yihui , He Biao , Kuchenbecker Kristopher M. , You Liang , Xu Zhidong , Mikami Iwao , Yagui‐Beltran Adam , Clement Genevieve , Lin Yu‐Ching , Okamoto Junichi , Bravo Dawn T. , Jablons David M.
Published: May 2007

Constitutive activation of the Wnt pathway as a result of APC, AXIN1 or CTNNB1 mutations has been found in most colorectal cancers. For a long time, this aberrant Wnt activation has been thought to be independent of upstream signals. However, recent studies indicate that upstream signals retain their ability to regulate the Wnt pathway even in the presence of downstream mutations. Wnt‐2 is well known for its overexpression in colorectal cancer. Galectin‐3 (Gal‐3), a multifunctional carbohydrate binding protein implicated in a variety of biological functions, has recently been reported to interact with β‐catenin. In this study, we investigated roles of Wnt‐2 and Gal‐3 in the regulation of canonical Wnt/β‐catenin signaling. We found that siRNA silencing of either Wnt‐2 or Gal‐3 expression inhibited TCF‐reporter activity, decreased cytosolic β‐catenin level and induced apoptosis in human colorectal cancer cells containing downstream mutations. More interestingly, we showed that inhibition of both Wnt‐2 and Gal‐3 had synergistic effects on suppressing canonical Wnt signaling and inducing apoptosis, suggesting that aberrant canonical Wnt/β‐catenin signaling in colorectal cancer can be regulated at multiple levels. The combined inhibition of Wnt‐2 and Gal‐3 may be of superior therapeutic advantage to inhibition by either one of them, giving rise to a potential development of novel drugs for the targeted treatment of colorectal cancer. © 2007 Wiley‐Liss, Inc.
Differential DNA methylation associated with hepatitis B virus infection in hepatocellular carcinoma
Authors: Su Pei‐Fen , Lee Te‐Chang , Lin Pei‐Ju , Lee Po‐Huang , Jeng Yung‐Ming , Chen Chien‐Hung , Liang Ja‐Der , Chiou Ling‐Ling , Huang Guan‐Tarn , Lee Hsuan‐Shu
Published: May 2007

Gene inactivation through DNA hypermethylation plays a pivotal role in carcinogenesis. This study aimed to profile aberrant DNA methylation in different stages of liver disease, namely noncirrhosis, cirrhosis and hepatocellular carcinoma (HCC), and also to clarify the influence of hepatitis B virus (HBV) infection on the aberrant DNA methylation in HCCs. Promoter methylation in p14ARF, p16INK4a, O6‐methylguanine‐DNA methyltransferase (MGMT), glutathione S‐transferase pi (GSTP1) and E‐cadherin (E‐Cad) genes of 58 HCCs paired with adjacent nontumorous tissues was assayed by methylation‐specific PCR. HBV infection was determined using a hepatitis B virus surface antigen (HBsAg) serological assay. The frequency of p16INK4a promoter methylation increased from noncirrhotic, cirrhotic, to HCC tissues (noncirrhotic vs. HCC, p < 0.001), while that of GSTP1 promoter methylation increased in cirrhotic tissues compared to noncirrhotic ones (p = 0.029). The frequency of GSTP1 promoter hypermethylation is significantly higher in HCC than in nontumorous tissues (p = 0.022) from HBsAg‐positive patients, but not the HBsAg‐negative controls (p = 0.289). While the frequency of E‐Cad promoter hypermethylation remained high in both nontumorous tissues and HCCs from HBsAg‐positive patients (p = 0.438), it was lower in HCCs than in nontumorous tissues from HBsAg‐negative patients (p = 0.002). In contrast, the frequency of p16INK4a, MGMT and p14ARF promoter hypermethylation in HCCs was unrelated to HBsAg status. In conclusion, aberrant DNA methylation may begin at different stages of liver disease in a gene‐dependent manner. Moreover, HBV infection may enhance or maintain GSTP1 and E‐Cad promoter methylation and thereby affect hepatocarcinogenesis. © 2007 Wiley‐Liss, Inc.
Alcohol and folate consumption and risk of benign proliferative epithelial disorders of the breast
Authors: Cui Yan , Page David L. , Chlebowski Rowan T. , Beresford Shirley A. , Hendrix Susan L. , Lane Dorothy S. , Rohan Thomas E.
Published: May 2007

Alcohol consumption has been associated with increased breast cancer risk and the increase in risk may be attenuated by adequate folate intake. However, their associations with the risk of benign proliferative epithelial disorders (BPEDs) of the breast, possible precursors of breast cancer, are not well understood. To investigate these associations, we conducted a cohort study among 68,132 postmenopausal women participating in the Women's Health Initiative randomized clinical trials. Women were prospectively followed and those reporting a breast procedure (open surgical biopsy or core needle biopsy) had histological sections obtained for central pathology review. A total of 1,792 women with BPED of the breast were identified over an average of 7.8 years of follow‐up. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence limits (CLs) for the associations of interest. Compared to nondrinkers, total current alcohol intake of 30 g/day or more was not associated with BPED risk (HR = 0.98, 95% CL = 0.70, 1.38). The risk of BPED was not associated with folate intake from diet (highest vs. lowest quartile: HR = 1.10, 95% CL = 0.96, 1.26), from supplements (yes vs. no: HR = 1.05, 95% CL = 0.96, 1.16) or from all sources combined (highest vs. lowest quartile: HR = 1.11, 95% CL = 0.96, 1.27). Furthermore, there was no effect modification between alcohol and folate in relation to the risk of BPED. In conclusion, we observed that alcohol consumption and folate intake were not associated with altered risk of BPED, and that there was no effect modification between them in relation to the risk of BPED. © 2007 Wiley‐Liss, Inc.
The falsity of the reconstruction conjecture for tournaments
Authors: Stockmeyer Paul K.
Published: May 2007

The conjecture that for all sufficiently large p any tournament of order p is uniquely reconstructable from its point‐deleted subtournaments is shown to be false. Counterexamples are presented for all orders of the form 2n + 1 and 2n + 2. The largest previously known counterexamples were of order 8.
Graphs with exactly one hamiltonian circuit
Authors: Sheehan John
Published: May 2007

Let h(n) be the largest integer such that there exists a graph with n vertices having exactly one Hamiltonian circuit and exactly h(n) edges. We prove that h(n) = [n2/4]+1 (n ≧ 4) and discuss some related problems.
Definitions of criticality with respect to edge‐coloring
Authors: Helton A. J. W.
Published: May 2007

Here we examine six definitions of criticality concerning the chromatic index (edge chromatic number) of a simple graph. Five of these turn out to be almost always almost equivalent. Some problems arise and some conjectures are posed.
The spanning subgraphs of eulerian graphs
Authors: Boesch F. T. , Suffel C. , Tindell R.
Published: May 2007

It is shown that a connected graph G spans an eulerian graph if and only if G is not spanned by an odd complete bigraph K(2m + 1, 2n + 1). A disconnected graph spans an eulerian graph if and only if it is not the union of the trivial graph with a complete graph of odd order. Exact formulas are obtained for the number of lines which must be added to such graphs in order to get eulerian graphs.
Some small ramsey numbers
Authors: Clancy M.
Published: May 2007

In previous work, the Ramsey numbers have been evaluated for all pairs of graphs with at most four points. In the present note, Ramsey numbers are tabulated for pairs F1, F2 of graphs where F1 has at most four points and F2 has exactly five points. Exact results are listed for almost all of these pairs.
Tree‐complete graph ramsey numbers
Authors: Chvátal V.
Published: May 2007

The ramsey number of any tree of order m and the complete graph of order n is 1 + (m − 1)(n − 1).
Extremal problems in graph theory
Authors: Bollobás Béla
Published: May 2007

The aim of this note is to give an account of some recent results and state a number of conjectures concerning extremal properties of graphs.
The combinatorial map color theorem
Authors: Ringel Gerhard
Published: May 2007

This paper is written in the spirit of the author's book: Map Color Theorem (1974). We try to develop the Map Color Theorem in a combinatorial way, circumventing the unwieldy embedding theory. Similar (but not identical) generalizations have recently and independently been developed by Alpert (in press) and by Stahl (in press). The first nine theorems are one‐dimensional versions of known facts from the theory of two‐dimensional compact manifolds. Theorems 10 to 13 are to my knowledge completely new results.
The number of connected sparsely edged graphs
Authors: Wright E. M.
Published: May 2007

An (n, q) graph has n labeled points, q edges, and no loops or multiple edges. The number of connected (n, q) graphs is f(n, q). Cayley proved that f(n, n‐1) = nn−2 and Renyi found a formula for f(n, n). Here I develop two methods to calculate the exponential generating function of f(n, n + k) for particular k and so to find a formula for f(n, n + k) for general n. The first method is a recurrent one with respect to k and is well adapted for machine computation, but does not itself provide a proof that it can be continued indefinitely. The second (reduction) method is much less efficient and is indeed impracticable for k greater than 2 or 3, but it supplies the missing proof that the generating function is of a particular form and so that the first method can be continued for all k, subject only to the capacity of the machine.
On independent circuits of a digraph
Authors: Kosaraju S. Rao
Published: May 2007

If every three circuits of a digraph have a common vertex, then all the circuits have one.
On the independence ratio of a graph
Authors: Albertson Michael O. , Hutchinson Joan P.
Published: May 2007

This paper presents some recent results on lower bounds for independence ratios of graphs of positive genus and shows that in a limiting sense these graphs have the same independence ratios as do planar graphs. This last result is obtained by an application of Menger's Theorem to show that every triangulation of a surface of positive genus has a short cycle which does not separate the graph and is non‐contractible on that surface.
Nearly acyclic graphs are reconstructible
Authors: Manvel Bennet , Weinstein Joseph M.
Published: May 2007

We prove that a graph G is reconstructible if G has a node v with G‐v acyclic. The proof uses colored graphs and shows how to reconstruct some graphs from pieces which share a common subgraph having few automorphisms.
On cycle—Complete graph ramsey numbers
Authors: Erdös P. , Faudree R. J. , Rousseau C. C. , Schelp R. H.
Published: May 2007

A new upper bound is given for the cycle‐complete graph Ramsey number r(Cm, Kn), the smallest order for a graph which forces it to contain either a cycle of order m or a set of n independent vertices. Then, another cycle‐complete graph Ramsey number is studied, namely r(⩽Cm, Kn) the smallest order for a graph which forces it to contain either a cycle of order / for some / satisfying 3⩽/⩽m or a set of n independent vertices. We obtain the exact value of r(⩽Cm Kn) for all m > n and an upper bound which applies when m is large in comparison with log n.
Ramsey numbers for multiple copies of complete graphs
Authors: Lorimer P. J. , Segedin R. J.
Published: May 2007

The Ramsey numbers r(m1Kp, …, mcK) are calculated to within bounds which are independent of m1, …, mc when c > 2 and p1, …, pc > 2.
Mixed ramsey numbers: Chromatic numbers versus graphs
Authors: Benedict James M. , Chartrand Gary , Lick Don R.
Published: May 2007

For positive integers n1, n2, …, nI and graphs GI+1, GI+2, …, Gk, 1 ≤ / < k, the mixed Ramsey number χ(n1, …, n1, GI+1, …, Gk) is define as the least positive integer p such that for each factorization Kp = F1⊕ … ⊕ F⊕ FI+1⊕ … ⊕ Fk, it it follows that χ(Fi) ≥ ni for some i, 1 ⩽ i ⩽ l, or Gi is a subgraph of Fi for some i, l < i ⩽ k. Formulas are presented for maxed Ramsey numbers in which the graphs GI+1, GI+2, …, Gk are connected, and in which k = I+1 and GI+1 is arbitray.
Some connected ramsey numbers
Authors: Faudree R. J. , Schelp R. H.
Published: May 2007

A graph G is co‐connected if both G and its complement Ḡ are connected and nontrivial. For two graphs A and B, the connected Ramsey number rc(A, B) is the smallest integer n such that there exists a co‐connected graph of order n, and if G is a co‐connected graph on at least n vertices, then A ⩽ G or B ⩽ Ḡ. If neither A or B contains a bridge, then it is known that rc(A, B) = r(A, B), where r(A, B) denotes the usual Ramsey number of A and B. In this paper rc(A, B) is calculated for some pairs (A, B) when r(A, B) is known and at least one of the graphs A or B has a bridge. In particular, rc(A, B) is calculated for A a path and B either a cycle, star, or complete graph, and for A a star and B a complete graph.
When the cartesian product of directed cycles is Hamiltonian
Authors: Trotter William T. , Erdös Paul
Published: May 2007

The cartesian product of two hamiltonian graphs is always hamiltonian. For directed graphs, the analogous statement is false. We show that the cartesian product Cn1 × Cn2 of directed cycles is hamiltonian if and only if the greatest common divisor (g.c.d.) d of n1 and n2 is at least two and there exist positive integers d1, d2 so that d1 + d2 = d and g.c.d. (n1, d1) = g.c.d. (n2, d2) = 1. We also discuss some number‐theoretic problems motivated by this result.
Perfect Elimination and Chordal Bipartite Graphs
Authors: Golumbic Martin Charles , Goss Clinton F.
Published: May 2007

We define two types of bipartite graphs, chordal bipartite graphs and perfect elimination bipartite graphs, and prove theorems analogous to those of Dirac and Rose for chordal graphs (rigid circuit graphs, triangulated graphs). Our results are applicable to Gaussian elimination on sparse matrices where a sequence of pivots preserving zeros is sought. Our work removes the constraint imposed by Haskins and Rose that pivots must be along the main diagonal.