bluuebunny/crossref_metadata_2025 huggingface dataset:
A Class of Permutation Tests for Stratified Survival Data
Authors: Shih Joanna H. , Fay Michael P.
Published: May 2004

Summary.We propose a class of permutation tests for stratified survival data. The tests are derived using the framework of Fay and Shih (1998,Journal of the American Statistical Association93, 387–396), which creates tests by permuting scores based on a functional of estimated distribution functions. Here the estimated distribution function for each possibly right‐, left‐, or interval‐censored observation is based on a shrinkage estimator similar to the nonparametric empirical estimator of Ghosh, Lahiri, and Tiwari (1989,Communications in Statistics—Theory and Methods18, 121–146), and permutation is carried out within strata. The proposed test with a weighted Mann‐Whitney functional is similar to the permutation form of the stratified log‐rank test when there is a large strata effect or the sample size in each stratum is large and is similar to the permutation form of the ordinary log‐rank test when there is little strata effect. Thus, the proposed test unifies the advantages of both the stratified and ordinary log‐rank tests. By changing the functional, we may obtain a stratified Prentice–Wilcoxon test or a difference in means test with similar unifying properties. We show through simulations the advantage of the proposed test over existing tests for uncensored and right‐censored data.
Polyhazard Models for Lifetime Data
Authors: Louzada‐Neto Francisco
Published: May 2004

Summary.We propose a polyhazard model to deal with lifetime data associated with latent competing risks. The causes of failure are assumed unobserved and affecting individuals independently. The general framework allows a broad class of hazard models that includes the most common hazard‐based models. The model accommodates bathtub and multimodal hazards, keeping enough flexibility for common lifetime data that cannot be accommodated by usual hazard‐based models. Maximum likelihood estimation is discussed, and parametric simulation is used for hypothesis testing.
Small‐Sample Confidence Regions in Exponential Families
Authors: Kolassa John E. , Tanner Martin A.
Published: May 2004

Summary.This article presents an algorithm for small‐sample conditional confidence regions for two or more parameters foranydiscrete regression model in the generalized linear interactive model family. Regions are constructed by careful inversion of conditional hypothesis tests. This method presupposes the use of approximate or exact techniques for enumerating the sample space for some components of the vector of sufficient statistics conditional on other components. Such enumeration may be performed exactly or by exact or approximate Monte Carlo, including the algorithms of Kolassa and Tanner (1994,Journal of the American Statistical Association89, 697–702; 1999,Biometrics55, 246–251). This method also assumes that one can compute certain conditional probabilities for a fixed value of the parameter vector. Because of a property of exponential families, one can use this set of conditional probabilities to directly compute the conditional probabilities associated with any other value of the vector of the parameters of interest. This observation dramatically reduces the computational effort required to invert the hypothesis test to obtain the confidence region. To construct a region with confidence level 1 –α, the algorithm begins with a grid of values for the parameters of interest. For each parameter vector on the grid (corresponding to the current null hypothesis), one transforms the initial set of conditional probabilities using exponential tilting and then calculates thepvalue for this current null hypothesis. The confidence region is the set of parameter values for which thepvalue is at least α.
Accounting for Variability in the Use of Permutation Testing to Detect Quantitative Trait Loci
Authors: Nettleton Dan , Doerge R. W.
Published: May 2004

Summary. Locating quantitative trait loci (QTL), or genomic regions associated with known molecular markers, is of increasing interest in a wide variety of applications ranging from human genetics to agricultural genetics. The hope of locating QTL (or genes) affecting a quantitative trait is that it will lead to characterization and possible manipulations of these genes. However, the complexity of both statistical and genetic issues surrounding the location of these regions calls into question the asymptotic statistical results supplying the distribution of the test statistics employed. Coupled with the power of current‐day computing, permutation theory was reintroduced for the purpose of estimating the distribution of any test statistic used to test for the location of QTL. Permutation techniques have offered an attractive alternative to significance measures based on asymptotic theory. The ideas of permutation testing are extended in this application to include confidence intervals for the thresholds and p‐values estimated in permutation testing procedures. The confidence intervals developed account for the Monte Carlo error associated with practical applications of permutation testing and lead to an effective method of determining an efficient permutation sample size.
Random Effects Modeling of Multiple Binomial Responses Using the Multivariate Binomial Logit‐Normal Distribution
Authors: Coull Brent A. , Agresti Alan
Published: May 2004

Summary. The multivariate binomial logit‐normal distribution is a mixture distribution for which, (i) conditional on a set of success probabilities and sample size indices, a vector of counts is independent binomial variates, and (ii) the vector of logits of the parameters has a multivariate normal distribution. We use this distribution to model multivariate binomial‐type responses using a vector of random effects. The vector of logits of parameters has a mean that is a linear function of explanatory variables and has an unspecified or partly specified covariance matrix. The model generalizes and provides greater flexibility than the univariate model that uses a normal random effect to account for positive correlations in clustered data. The multivariate model is useful when different elements of the response vector refer to different characteristics, each of which may naturally have its own random effect. It is also useful for repeated binary measurement of a single response when there is a nonexchangeable association structure, such as one often expects with longitudinal data or when negative association exists for at least one pair of responses. We apply the model to an influenza study with repeated responses in which some pairs are negatively associated and to a developmental toxicity study with continuation‐ratio logits applied to an ordinal response with clustered observations.
A Graphical Method for Finding Maximin Efficiency Designs
Authors: Imhof Lorens , Wong Weng Kee
Published: May 2004

Summary.We consider the problem of designing an experiment when there are two competing optimality criteria. Designs that maximize the minimum efficiencies under the two criteria are proposed along with a graphical method for finding these maximin designs.
Substantial Gains in Bias Reduction from Matching with a Variable Number of Controls
Authors: Ming Kewei , Rosenbaum Paul R.
Published: May 2004

Summary.In observational studies that match several controls to each treated subject, substantially greater bias reduction is possible if the number of controls is not fixed but rather is allowed to vary from one matched set to another. In certain cases, matching with a fixed number of controls may remove only 50% of the bias in a covariate, whereas matching with a variable number of controls may remove 90% of the bias, even though both control groups have the same number of controls in total. An example of matching in a study of surgical mortality is discussed in detail.
A Homogeneity Test in Overviews with Group Sequentially Monitored Clinical Trials
Authors: Li Zhengqing , Li Yan
Published: May 2004

Summary. It is known that using statistical stopping rules in clinical trials can create an artificial heterogeneity of treatment effects in overviews of related trials (Hughes, Preedman, and Pocock, 1992, Biometrics48, 41–53). If the true treatment effect being tested is small, as is often the case, the homogeneity test by DerSimonian and Laird (1986, Controlled Clinical Trials7, 177–188) violates the size of the test very severely. This paper provides a new homogeneity test, which preserves the size of the test more accurately. The operating characteristics of the new test are examined through simulations.
Negative Binomial Additive Models
Authors: Thurston Sally W. , Wand M. P. , Wiencke John K.
Published: May 2004

Summary.The generalized additive model is extended to handle negative binomial responses. The extension is complicated by the fact that the negative binomial distribution has two parameters and is not in the exponential family. The methodology is applied to data involving DNA adduct counts and smoking variables among ex‐smokers with lung cancer. A more detailed investigation is made of the parametric relationship between the number of adducts and years since quitting while retaining a smooth relationship between adducts and the other covariates.
Testing Equality of Survival Functions Based on Both Paired and Unpaired Censored Data
Authors: Dallas Michael J. , Rao P. V.
Published: May 2004

Summary. We introduce two test procedures for comparing two survival distributions on the basis of randomly right‐censored data consisting of both paired and unpaired observations. Our procedures are based on generalizations of a pooled rank test statistic previously proposed for uncensored data. One generalization adapts the Prentice–Wilcoxon score, while the other adapts the Akritas score. The use of these particular scoring systems in pooled rank tests with randomly right‐censored paired data has been advocated by several researchers. Our test procedures utilize the permutation distributions of the test statistics based on a novel manner of permuting the scores. Permutation versions of tests for right‐censored paired data and for two independent right‐censored samples that use the proposed scoring systems are obtained as special cases of our test procedures. Simulation results show that our test procedures have high power for detecting scale and location shifts in exponential and log‐logistic distributions for the survival times. We also demonstrate the advantages of our test procedures in terms of utilizing randomly occurring unpaired observations that are discarded in test procedures for paired data. The tests are applied to skin graft data previously reported elsewhere.
A Linear Mixed‐Effects Model for Multivariate Censored Data
Authors: Pan Wei , Louis Thomas A.
Published: May 2004

Summary.We apply a linear mixed‐effects model to multivariate failure time data. Computation of the regression parameters involves the Buckley‐James method in an iterated Monte Carlo expectation‐maximization algorithm, wherein the Monte Carlo E‐step is implemented using the Metropolis‐Hastings algorithm. From simulation studies, this approach compares favorably with the marginal independence approach, especially when there is a strong within‐cluster correlation.
Estimation of Sojourn Time in Chronic Disease Screening Without Data on Interval Cases
Authors: Chen Tony H. H. , Kuo H. S. , Yen M. F. , Lai M. S. , Tabar L. , Duffy S. W.
Published: May 2004

Summary. Estimation of the sojourn time on the preclinical detectable period in disease screening or transition rates for the natural history of chronic disease usually rely on interval cases (diagnosed between screens). However, to ascertain such cases might be difficult in developing countries due to incomplete registration systems and difficulties in follow‐up. To overcome this problem, we propose three Markov models to estimate parameters without using interval cases. A three‐state Markov model, a five‐state Markov model related to regional lymph node spread, and a five‐state Markov model pertaining to tumor size are applied to data on breast cancer screening in female relatives of breast cancer cases in Taiwan. Results based on a three‐state Markov model give mean sojourn time (MST) 1.90 (95% CI: 1.18–4.86) years for this high‐risk group. Validation of these models on the basis of data on breast cancer screening in the age groups 50–59 and 60–69 years from the Swedish Two‐County Trial shows the estimates from a three‐state Markov model that does not use interval cases are very close to those from previous Markov models taking interval cancers into account. For the five‐state Markov model, a reparameterized procedure using auxiliary information on clinically detected cancers is performed to estimate relevant parameters. A good fit of internal and external validation demonstrates the feasibility of using these models to estimate parameters that have previously required interval cancers. This method can be applied to other screening data in which there are no data on interval cases.
Analysis of a Two‐Stage Case–Control Study with Cluster Sampling of Controls: Application to Nonmelanoma Skin Cancer
Authors: Fears Thomas R. , Gail Mitchell H.
Published: May 2004

Summary.We present a pseudolikelihood approach for analyzing a two‐stage population‐based case‐control study with cluster sampling of controls. These methods were developed to analyze data from a study of nonmelanoma skin cancer (NMSC). This study was designed to evaluate the role of ultraviolet radiation (UVB) on NMSC risk while adjusting for age group, which is known for all subjects, and for other individual‐level factors, such as susceptibility to sunburn, which are known only for participants in the case‐control study. The methods presented yield estimates of relative and absolute risk, with standard errors, while accounting naturally for the two‐stage sampling of the cohort and cluster sampling of controls.
A Multiple Imputation Approach to Cox Regression with Interval‐Censored Data
Authors: Pan Wei
Published: May 2004

Summary.We propose a general semiparametric method based on multiple imputation for Cox regression with interval‐censored data. The method consists of iterating the following two steps. First, from finite‐interval‐censored (but not right‐censored) data, exact failure times are imputed using Tanner and Wei's poor man's or asymptotic normal data augmentation scheme based on the current estimates of the regression coefficient and the baseline survival curve. Second, a standard statistical procedure for right‐censored data, such as the Cox partial likelihood method, is applied to imputed data to update the estimates. Through simulation, we demonstrate that the resulting estimate of the regression coefficient and its associated standard error provide a promising alternative to the nonparametric maximum likelihood estimate. Our proposal is easily implemented by taking advantage of existing computer programs for right–censored data.
Approximate Bayesian Evaluation of Multiple Treatment Effects
Authors: Thall Peter F. , Simon Richard M. , Shen Yu
Published: May 2004

Summary.We propose an approximate Bayesian method for comparing an experimental treatment to a control based on a randomized clinical trial with multivariate patient outcomes. Overall treatment effect is characterized by a vector of parameters corresponding to effects on the individual patient outcomes. We partition the parameter space into four sets where, respectively, the experimental treatment is superior to the control, the control is superior to the experimental, the two treatments are equivalent, and the treatment effects are discordant. We compute posterior probabilities of the parameter sets by treating an estimator of the parameter vector like a random variable in the Bayesian paradigm. The approximation may be used in any setting where a consistent, asymptotically normal estimator of the parameter vector is available. The method is illustrated by application to a breast cancer data set consisting of multiple time‐to‐event outcomes with covariates and to count data arising from a cross‐classification of response, infection, and treatment in an acute leukemia trial.
Morphometric and immunohistochemical study of the rumen of red deer during prenatal development
Authors: Franco A. J. , Masot A. J. , Aguado Ma C. , Gómez L. , Redondo E.
Published: May 2004

A detailed study of the ontogenesis of deer stomach has not been undertaken to date, and our aim was to sequence several histological phenomena that occur during the ontogenesis of one of the gastric compartments, the rumen. Histomorphometric and immunohistochemical analyses were carried out on 50 embryos and fetuses of deer from the initial stages of prenatal life until birth. For the purposes of testing, the animals were divided into five experimental groups: group I, 1.4–3.6 cm crown–rump length, 30–60 days, 1–25% of gestation; group II, 4.5–7.2 cm crown–rump length, 67–90 days, 25–35% of gestation; group III, 8–19 cm crown–rump length, 97–135 days, 35–50% of gestation; group IV, 21–33 cm crown–rump length, 142–191 days, 45–70% of gestation; and group V, 36–40 cm crown–rump length, 205–235 days, 75–100% of gestation. The rumen of the primitive gastric tube was observed at approximately 60 days. At 67 days the rumen consisted of three layers: internal or mucosal, middle or muscular, and external or serosal layer. The stratification of the epithelial layer was accompanied by changes in its structure with the appearance of ruminal pillars and papillae. The outline of the ruminal papillae began to appear at 142 days of prenatal development as evaginations of the basal zone toward the ruminal lumen, pulling with it in its configuration the stratum basale, the lamina propria and the submucosa. From the pluripotential blastemic tissue at 60 days we witnessed the histodifferentiation of the primitive tunica muscularis, composed of two layers of myoblasts with a defined arrangement. It was also from the pluripotential blastemic tissue, at 97 days, that the lamina propria and the submucosa were differentiated. The serosa showed continuity in growth as well as differentiation, already detected in the undifferentiated outline phase. The tegumentary mucosa of deer rumen was shown without secretory capacity in the initial embryonic phases; neutral mucopolysaccharides appeared from 67 days. The presence of neuroendocrine cells (non‐neuronal enolase) in the ruminal wall of deer during development was not detected until 97 days. The glial cells were detected at 142 days for glial fibrillary acidic protein and at 67 days for vimentin. The immunodetection of neuropeptides vasointestinal peptide and neuropeptide Y progressively increased with gestation period, starting from 97 days. In terms of the structure of the rumen of the primitive gastric tube, our observations revealed that the deer is less precocious than small and large domestic ruminants. Thus its secretory capacity, detected by the presence of neutral mucopolysaccharides, and its neuroendocrine nature, determined by the presence of positive non‐neuronal enolase cells, were evident in more advanced stages of prenatal development than those detected in the sheep, goat and cow.
Research and Development in Computable Production Functions
Authors: Luna Francesco
Published: May 2004

In this paper, transmissibility and replicability of blueprints confine production functions to computable processes. The immediate consequence is that research and development and the emergence of technological innovations are naturally embedded in computable production functions. There is no need to introduce ad hoc probability distributions to model the arrival of innovations as the uncertain result of research and development activity. Rather, in this approach, well‐known results like the halting problem or Rice theorem harness production theory so as to encompass product and process innovation.
Emergence and Universal Computation
Authors: Lee Cassey
Published: May 2004

Emergence refers to the spontaneous formation of higher level (macro) structures or patterns in complex systems. Attempts to formalize the notion of emergence via algorithmic complexity theory runs into the problem that the Kolmogorov complexity function is not computable. The reason for this motivates a closer examination of the link between emergence and universal computation. Following Wolfram's pioneering work in the classification of cellular automata behavior, the research programs of Langton and Crutchfield, while incomplete, provide important insights to economists seeking to understand the relevance of emergence and universal computation to their discipline. They lead to questions on the emergence of institutions and the concomitant changes in rule‐based behavior on the part of economic agents.
Rights and Decentralized Computation
Authors: Holm Håkan J.
Published: May 2004

This paper emphasizes that rights facilitate decentralized use of information and computation. A dynamically efficient adjustment process that solves a private information linear resource allocation problem by a sequential auction of production and trading rights is presented. It is shown that in equilibrium the sequential auction mimics the simplex algorithm in a decentralized way and thereby gives it an institutional economic interpretation, where the structure of rights imposes restrictions on the problem sequentially.
Oviposition preference and larval performance within a diverging lineage of lycaenid butterflies
Authors: Forister Matthew L.
Published: May 2004

Abstract.1. The butterfly genusMitourain Northern California includes three nominal species associated with four host plants having parapatric or interdigitated ranges. Genetic analyses have shown the taxa to be very closely related, and adults from all host backgrounds will mate and produce viable offspring in the laboratory. Oviposition preference and larval performance were investigated with the aim of testing the hypothesis that variation in these traits can exist in a system in which non‐ecological barriers to gene flow (i.e. geographic barriers and genetic incompatibilities) appear to be minimal.

2. Females were sampled from 12 locations throughout Northern California, including sympatric and parapatric populations associated with the four different host‐plant species. Oviposition preference was assayed by confining wild‐caught females with branches of all four host species and counting the number of eggs laid on each. Offspring were reared on the same host species and two measures of larval success were taken: per cent survival and pupal weight.

3. For populations associated with one of the hosts, incense cedar, the preference–performance relationship is simple: the host that females chose is the plant which results in the highest pupal weights for offspring. The preference–performance relationship for populations associated with the other hosts is more complex and may reflect different levels of local adaptation. The variation in preference and performance reported here suggests that these traits can evolve when non‐ecological barriers to gene flow are low, and that differences in these traits may be important for the evolution of reproductive isolation withinMitoura.
Aerial dispersal and host plant selection by neonate Thyridopteryx ephemeraeformis (Lepidoptera: Psychidae)
Authors: Moore Robert G. , Hanks Lawrence M.
Published: May 2004

Abstract.  1. Neonate evergreen bagworms, Thyridopteryx ephemeraeformis (Haworth) (Lepidoptera: Psychidae), disperse by dropping on a strand of silk, termed silking, and ballooning on the wind. Larvae construct silken bags with fragments of plant foliage. This species is highly polyphagous, feeding on more than 125 species of woody plants of 45 families. The larvae commonly infests juniper (Juniperus spp.) and arborvitae (Thuja spp.), but rarely feed on deciduous hosts such as maples. The hypothesis is proposed that polyphagy in T. ephemeraeformis is maintained by variation among larvae in dispersal behaviour, and time constraints on the opportunity to disperse, but patterns of host species preference result from a predisposition for larvae to settle on arborvitae and juniper but disperse from other hosts.

2. Consistent with that hypothesis, laboratory experiments revealed: (a) starved larvae varied in their tendency to disperse from paper leaf models; (b) starved larvae readily silked only during their first day; (c) larvae became increasingly sedentary the longer they were exposed to plant foliage; (d) when provided with several opportunities to silk, larvae became sedentary after exposure to arborvitae foliage, but repeatedly silked after exposure to maple (Acer species) foliage or paper; and (e) larvae were less inclined to silk from foliage of arborvitae than from maple.

3. Field experiments supported the hypothesis by demonstrating that: (a) neonates tended to disperse from maple leaves while larvae older than 1 day tended to settle and remain; and (b) neonates were less likely to disperse from arborvitae and juniper trees than from maples.
Incomplete Information, Trading Costs and Cross‐autocorrelations in Stock Returns
Authors: Chordia Tarun , Swaminathan Bhaskaran
Published: May 2004

This paper provides an economic rationale for the cross‐autocorrelation patterns in stock returns in the context of a microstructure model in which investors have incomplete information. The paper shows that in a market in which investors are informed about only a sub‐set of stocks, the emergence of lead‐lag, cross‐autocorrelations is a function of the cost of trading in other stocks based on information about the sub‐set of stocks. If cross‐trading costs are high, informed investors will trade only in the sub‐set of stocks they are informed about; if cross‐trading costs are moderate, informed investors will randomize between trading and not trading in other stocks; and if cross‐trading costs are low, they will trade in all stocks. When informed investors trade only in a sub‐set of stocks, prices of stocks with more informed trading will adjust to common factor information faster than the prices of stocks with less informed trading giving rise to asymmetric lead‐lag cross‐autocorrelations. When informed investors trade in all stocks, asymmetric lead‐lag cross‐autocorrelations will disappear as a result of their cross‐market arbitrage trading. These results provide a number of testable implications for lead‐lag cross‐autocorrelation patterns. The data is consistent with the empirical predictions.

(J.E.L.G12, G14).
A market without the ‘right’ property rights
Authors: Kim Annette M.
Published: May 2004

While Vietnam's reforms provided some of the weakest legal private property rights amongst the transitions countries, cities like Ho Chi Minh City have booming domestic real estate markets. Interestingly, while most properties in 2001 did not have legal title, those on the market did advertise a variety of property rights claims. Employing a hedonic price model to analyse the pattern of prices at which sellers offer properties in Ho Chi Minh City, this study examines how this market values property rights. The findings show that multiple forms of property rights, enforced by highly decentralized state institutions, are operational in this market. Furthermore, legal title itself is not the most valuable form of property right. These findings suggest that the value of property rights emanates from where it is enforced within the particular institutional context of a market.
Prognosis of large cyst‐like periapical lesions following nonsurgical root canal treatment: a clinical review
Authors: Çalışkan M. K.
Published: May 2004

Aim  To evaluate clinically and radiographically the long‐term clinical outcome of nonsurgical root canal treatment using calcium hydroxide in teeth with large cyst‐like periapical lesions.

Summary  A total of 42 mature anterior teeth with large periapical lesions ranging in size from 7 to 18 mm in diameter were included in this study. Fluid samples from the lesions contained cholesterol crystals, which were identified by light microscopy. After adequate draining, the teeth were treated endodontically using calcium hydroxide as the intracanal medicament. All cases were followed up for a period of 2–10 years. Complete healing was observed in 73.8% and incomplete healing in a further 9.5% of cases.

Key learning points

• Root canal treatment using calcium hydroxide as an antibacterial dressing was successful in healing large cyst‐like periapical lesions.

• This study suggests that the size of a periapical lesion is not a major determining factor in the decision to perform conventional root canal treatment or surgical removal of the lesion. Even large cyst‐like periapical lesions containing cholesterol crystals can heal following nonsurgical root canal treatment.
An evaluation of the use of tooth temperature to assess human pulp vitality
Authors: Smith E. , Dickson M. , Evans A. L. , Smith D. , Murray C. A.
Published: May 2004

Aim  To evaluate change in tooth surface temperature following a thermal stimulus as a simple and reliable method to assess the presence and the extent of blood flow through teeth.

Methodology  Miniature thermometers were used to measure the relationship between surface temperature of teeth and internal flow of 37 °C water (in vitro) or blood (in vivo). In addition, thermal stimuli were applied to the external surface of the teeth, and the rate of temperature recovery was related to internal flow.

Results  Under in vitro conditions, the surface temperature of teeth and rate of temperature recovery were related to the rate of internal water flow. However, in vivo neither standing surface temperature (P = 0.47) nor rate of temperature recovery (P = 0.19) were significantly related to evidential pulp vitality.

Conclusion  Change in the surface temperature of teeth is not suitable as a simple clinical means to assess pulp vitality.
Prevalence of and factors affecting post‐obturation pain in patients undergoing root canal treatment
Authors: Ng Y.‐L. , Glennon J. P. , Setchell D. J. , Gulabivala K.
Published: May 2004

Aim  This longitudinal, prospective study (1) investigated the prevalence of post‐obturation pain after root canal treatment and (2) evaluated the influence of factors affecting the pain experience.

Methodology  Twenty practitioners, comprising general dental practitioners, MSc graduates and Endodontists, participated in this study. The patient sample (n = 415) was derived from consecutive patients attending the practitioners’ surgeries for root canal treatment on a single tooth. Demographic, medical history, preoperative and intra‐operative data as well as pain experience on day 1 and day 2 after root canal obturation were recorded. Intensity of pain experienced was recorded on a visual analogue scale (VAS) of 0–5. The data were analysed using logistic regression models.

Results  The prevalence of post‐obturation pain within 48 h after treatment was 40.2% (n = 167) but less than 12% of patients experienced severe pain (VAS 4 or 5) on either day 1 or day 2. The factors that significantly influenced post‐obturation pain experience were: gender (OR = 0.434, P < 0.001), tooth type (OR = 1.733, P = 0.007), size of periapical lesion (OR = 0.493, P = 0.004), history of post‐preparation pain (OR = 4.110, P = <0.001) or generalized swelling (OR = 3.435, P = 0.005) and number of treatment visits (OR = 2.604, P < 0.001).

Conclusions  The prevalence of post‐obturation pain was high (40.2%). The important prognostic determinants of post‐obturation pain were female, molar tooth, size of periapical lesion smaller than 3 mm, history of post‐preparation pain or generalized swelling and single‐visit treatment.
The Synechococcus elongatus PII signal transduction protein controls arginine synthesis by complex formation with N‐acetyl‐l‐glutamate kinase
Authors: Heinrich Annette , Maheswaran Mani , Ruppert Ulrike , Forchhammer Karl
Published: May 2004

This communication identifies, for the first time, a receptor protein for signal perception from the PII signal transduction protein in the cyanobacterium Synechococcus elongatus. PII, a phosphoprotein that signals the carbon/nitrogen status of the cells, forms a tight complex with the key enzyme of the arginine biosynthetic pathway, N‐acetylglutamate (NAG) kinase. In complex with PII, the catalytic activity of NAG kinase is strongly enhanced. Complex formation does not require the effector molecules of PII, 2‐oxoglutarate and ATP, but it is highly susceptible to modifications at the phosphorylation site of PII, Ser‐49. Stable complexes were only formed with the non‐phosphorylated form of PII but not with Ser‐49 mutants. In accordance with these data, NAG kinase activity in S. elongatus extracts correlated with the phosphorylation state of PII, with high NAG kinase activities corresponding to non‐phosphorylated PII (nitrogen‐excess conditions) and low activities to increased levels of PII phosphorylation (nitrogen‐poor conditions), thus subjecting the key enzyme of arginine biosynthesis to global nitrogen control.
Structure, function and evolution of microbial adenylyl and guanylyl cyclases
Authors: Baker David A. , Kelly John M.
Published: May 2004

Cells respond to signals of both environmental and biological origin. Responses are often receptor mediated and result in the synthesis of so‐called second messengers that then provide a link between extracellular signals and downstream events, including changes in gene expression. Cyclic nucleotides (cAMP and cGMP) are among the most widely studied of this class of molecule. Research on their function and mode of action has been a paradigm for signal transduction systems and has shaped our understanding of this important area of biology. Cyclic nucleotides have diverse regulatory roles in both unicellular and multicellular organisms, highlighting the utility and success of this system of molecular communication. This review will examine the structural diversity of microbial adenylyl and guanylyl cyclases, the enzymes that synthesize cAMP and cGMP respectively. We will address the relationship of structure to biological function and speculate on the complex origin of these crucial regulatory molecules. A review is timely because the explosion of data from the various genome projects is providing new and exciting insights into protein function and evolution.
Excision of the high‐pathogenicity island of Yersinia pseudotuberculosis requires the combined actions of its cognate integrase and Hef, a new recombination directionality factor
Authors: Lesic Biliana , Bach Sandrine , Ghigo Jean‐Marc , Dobrindt Ulrich , Hacker Jörg , Carniel Elisabeth
Published: May 2004

Summary The Yersinia high‐pathogenicity island (HPI) encodes the siderophore yersiniabactin‐mediated iron uptake system. The HPI of Yersinia pseudotuberculosis I has previously been shown to be able to excise precisely from the bacterial chromosome by recombination between the attB‐R and attB‐L sites flanking the island. However, the nature of the Y. pseudotuberculosis HPI excision machinery remained unknown. We show here that, upon excision, the HPI forms an episomal circular molecule. The island thus has the ability to excise from the chromosome, circularize and reintegrate itself, either in the same location or in another asn tRNA copy. We also demonstrate that the HPI‐encoded bacteriophage P4‐like integrase (Int) plays a critical role in HPI excision and that, like phage integrases, it acts as a site‐specific recombinase that catalyses both excision and integration reactions. However, Int alone cannot efficiently promote recombination between the attB‐R and attB‐L sites, and we demonstrate that a newly identified HPI‐borne factor, designated Hef (for HPI excision factor) is also required for this activity. Hef belongs to a family of recombination directionality factors. Like the other members of this family, Hef probably plays an architectural rather than a catalytic role and promotes HPI excision from the chromosome by driving the function of Int towards an excisionase activity. The fact that the HPI, and probably several other pathogenicity islands, carry a machinery of integration/excision highly similar to those of bacteriophages argues for a phage‐mediated acquisition and transfer of these elements.
MONETARY POLICY IN ECONOMIES WITH LITTLE OR NO MONEY
Authors: McCallum Bennett T.
Published: May 2004

Abstract.  (1) Medium‐of‐exchange money will not entirely disappear in the foreseeable future. (2) In economies with no currency but settlement balances at the central bank, policy can be conducted much as at present by activist adjustment of overnight interest rates. (3) In economies without any money there can be no monetary policy. Liabilities of some official entity might serve as the medium of account, but there could be rivals. (4) A broad commodity‐bundle monetary standard could be viable, even with a redemption medium, and there is scope for quantitative analysis of such systems. (5) The number of distinct national currencies may decline sharply.
Effects of Changes in Family Composition and Employment Patterns on the Distribution of Income in Australia: 1981–1982 to 1997–1998
Authors: Johnson David , Wilkins Roger
Published: May 2004

We examine income distributions over the last two decades, presenting both non‐parametric kernel density estimates and summary measures. Standard errors of summary measures are also reported to facilitate statistical inference. We find a significant increase in private income inequality, but only a modest increase in disposable income inequality, implying an increase in the inequality‐reducing effects of income taxes and transfers. Using a semi‐parametric procedure developed by DiNardo et al. (1996), we then examine the effects of changes in family characteristics on the distribution of private income, finding that half the increase in inequality is explained by changes in the distribution of employment.
Exchanging access goods for access: A comparative study of business lobbying in the European Union institutions
Authors: BOUWEN PIETER
Published: May 2004

Abstract. The aim of this article is to test empirically a theory of access that investigates the logic behind the apparentad hoclobbying behavior of business interests in the European Union (EU) multi‐level system. First, a theoretical framework is set out that attempts to explain the access of different organizational forms of business interest representation – companies, associations and consultants – to the European Commission, the European Parliament and the Council of Ministers. The degree of access to these institutions is explained in terms of a theory of the supply and demand of access goods. Access goods concern information that is crucial in the EU policy‐making process. In return for access to an EU institution, business interests have to provide the access good(s) demanded by that institution. A number of specific hypotheses about access are analyzed in an extensive empirical study of the EU financial services sector. On the basis of 126 exploratory and semi‐structured interviews, the hypotheses are checked across the three EU institutions.
Tolerance, protest and democratic transition: Survey evidence from 13 post‐communist countries
Authors: GUÉRIN DANIEL , PETRY FRANÇOIS , CRÊTE JEAN
Published: May 2004

Abstract. Based on survey evidence in 13 post‐communist countries of Central and Eastern Europe, we show that citizens who engage in protest activities are more tolerant than those who do not take part in such activities. We argue that these ‘protesters’ have the potential to play a pivotal role in the democratic consolidation process currently under way in post‐communist countries. Our findings are compatible with earlier results that suggest that the remaking of political culture, in societies where radical social and political changes have been taking place, might be accomplished through concrete experience with the democratic process rather than through adherence to abstract democratic norms.
Veto players and the structure of budgets in advanced industrialized countries
Authors: TSEBELIS GEORGE , CHANG ERIC C. C.
Published: May 2004

Abstract.  This article tests expectations generated by the veto players theory with respect to the over time composition of budgets in a multidimensional policy space. The theory predicts that countries with many veto players (i.e., coalition governments, bicameral political systems, presidents with veto) will have difficulty altering the budget structures. In addition, countries that tend to make significant shifts in government composition will have commensurate modifications of the budget. Data collected from 19 advanced industrialized countries from 1973 to 1995 confirm these expectations, even when one introduces socioeconomic controls for budget adjustments like unemployment variations, size of retired population and types of government (minimum winning coalitions, minority or oversized governments). The methodological innovation of the article is the use of empirical indicators to operationalize the multidimensional policy spaces underlying the structure of budgets. The results are consistent with other analyses of macroeconomic outcomes like inflation, budget deficits and taxation that are changed at a slower pace by multiparty governments.
Politicisation, economic development and political interest in Europe
Authors: VAN DETH JAN W. , ELFF MARTIN
Published: May 2004

Abstract.  Political interest is usually depicted as an individual attribute that can be explained by referring to the resources and skills of citizens. The analyses presented here are based on a critical assessment of the explanatory power of these approaches in cross‐national and longitudinal comparisons. A contextual model is presented emphasising the relevance of distinct degrees of politicisation and economic development in different societies in addition to traditional sociodemographic factors (education, date of birth and gender) at the microlevel. The resulting multilevel model combines both individual and contextual factors to explain the cross‐national differences and changes in political involvement and apathy in Europe in the last three decades. The politicisation thesis, which states that the level of political interest among citizens is an increasing function of the relevance of societal and political arrangements in a society, is not supported by the empirical findings presented here. The most noteworthy conclusion is the remarkable disappearance of the impact of societal politicisation when the level of economic development of each country is included in multilevel models. The level of political interest, then, clearly depends on the level of economic development.
Use of a Sterile, Disposable, Radiation‐Absorbing Shield Reduces Occupational Exposure to Scatter Radiation During Pectoral Device Implantation
Authors: SIMONS GRANT R. , ORRISON WILLIAM W.
Published: May 2004

The aim of this study was to demonstrate the effectiveness of a radiation‐absorbing shield in reducing physicians' occupational radiation exposure during pectoral device implantation. A sterile, disposable, lead‐free radiation‐absorbing surgical drape containing x‐ray attenuation material was evaluated. Twenty procedures used the radiation absorbing drape, and 20 were performed without the shielding. Radiation exposure was measured using thermoluminescent dosimetry collar badges. Use of the protective shield was associated with a time adjusted 80% reduction in radiation dose (0.009 mrem/s with shielding vs 0.047 mrem/s without shielding, P < 0.05) to the physician performing the procedures. The radiation‐absorbing surgical drape did not interfere with technical performance nor add procedural time, and all procedures were successfully completed. This study demonstrates that a sterile, disposable, radiation‐absorbing drape provides a convenient means of augmenting conventional radiation shielding. Use of this protective shielding greatly reduces operators' occupational exposure to scatter radiation during pectoral device implantation without compromising sterility or procedural technique. (PACE 2004; 27[Pt. I]:726–729)
Technical Aspects of Implantation of LV Lead for Cardiac Resynchronization Therapy in Chronic Heart Failure
Authors: KAUTZNER JOSEF , RIEDLBAUCHOVÁ LUCIE , C̆IHÁK ROBERT , BYTEŠNÍK JAN , VANC̆URA VLASTIMIL
Published: May 2004

The goal of this study was to analyze total procedural and fluoroscopic time during initial experience with implantation of LV lead in a single center, and to assess the performance of electrophysiologically‐guided approach for cannulation of the coronary sinus (CS) in a subsequent period. Over an initial period of 29 months, a total of 46 attempts to implant biventricular pacing system were revised. During the first phase, only one type of LV electrode was available for three implanters (11 attempts). The second phase covered their early experience with other stylet‐controlled LV leads (10 attempts). Additional LV leads including the over‐the‐wire design were available in the third phase and 25 attempts were done by he most experienced implanter. In a period of advanced experience, 92 implant procedures performed by four implanters using an electrophysiologically‐guided approach to CS cannulation were revised. In the first period, success rates for different phases reached 70%, 90%, and 96%, respectively. Significant decrease in both procedural and fluoroscopic times was achieved with increased experience (Phase I: 247.1 ± 104.5 minutes and 31.2 ± 34.3 minutes, Phase II: 219.4 ± 85.6 minutes, and 22.9 ± 19.1 minutes, Phase III: 116.4 ± 89.9 minutes and 6.6 ± 4.4 minutes, respectively, P < 0.05). Advanced experience with electrophysiologically‐guided approach to CS cannulation allowed achievement of this target within a reasonable amount of time (15.4 ± 16.3 minutes) and with minimum fluoroscopic time (2.1 ± 2.9 minutes). In conclusion, both individual learning curve and technical advances significantly influence success rate, procedural, and fluoroscopic times for biventricular system implantation. Electrophysiologically‐guided approach makes cannulation of the CS a highly reproducible procedure that requires minimum fluoroscopic time. (PACE 2004; 27[Pt. I]:783–790)
Radiofrequency Catheter Ablation of a Macroreentrant Ventricular Tachycardia Late After Surgical Repair of Tetralogy of Fallot Using the Electroanatomic Mapping (CARTO)
Authors: ROSTOCK THOMAS , WILLEMS STEPHAN , VENTURA RODOLFO , WEISS CHRISTIAN , RISIUS TIM , MEINERTZ THOMAS
Published: May 2004

This case report describes a patient with a sustained monomorphic VT after surgical repair of a tetralogy of Fallot (TOF). In combination with the three‐dimensional electroanatomic mapping system, CARTO, and conventional mapping techniques the VT was identified as a macro‐reentrant tachycardia circling around the border between pulmonary graft and right ventricular outflow tract (RVOT). A y‐shaped ablation line crossing this zone was created. The VT terminated during RF application and was not inducible again. This case underlines the use of a combined conventional and three‐dimensional electroanatomic mapping technique can be helpful for catheter ablation of ventricular arrhythmias in TOF patients. (PACE 2004; 27[Pt. I]:801–804)
Inferolateral Myocardial Perfusion Defect Caused by Right Ventricular Outflow Tract Pacing
Authors: ERDOGAN OKAN , ALTUN ARMAGAN , DURMUS‐ALTUN GULAY , OZBAY GULTAC
Published: May 2004

This case report describes a patient who was free of coronary artery disease and showed reversible inferolateral myocardial perfusion defect after having undergone a permanent dual chamber pacemaker implantation and an active‐fixation ventricular lead insertion in the right ventricular outflow tract. (PACE 2004; 27[Pt. I]:808–811)
QT Dynamics and the Risk of Sudden Arrhythmic Cardiac Death in Ischemic Heart Disease
Authors: SREDNIAWA BEATA , JARSKI PIOTR , MUSIALIK‐LYDKA AGATA , KALARUS ZBIGNIEW , POLONSKI LECH
Published: May 2004

The relationship between altered QT dynamics and the risk of sudden arrhythmic death has not been established so far. This article describes the behavior of QT dynamics assessed in a patient with ischemic heart disease after two documented cardiac arrests due to sustained ventricular arrhythmia. (PACE 2004; 27[Pt. I]:827–828)