bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical properties and three‐body wear of veneering composites and their matrices
Authors: Reich Sven M. , Petschelt Anselm , Wichmann Manfred , Frankenberger Roland
Published: March 2004

Fatigue as one of the major factors affecting three‐body wear of resin composites is influenced by mechanical properties of the resin matrix. The aim of this in vitro study was to determine three‐body wear (ACTA methodology), fracture strength, and Young's modulus of four veneering composites (Artglass old and new formula, Vita Zeta LC Composite, Targis) and one direct restorative composite (Z 100). Furthermore, three‐body wear of the pure matrices of the materials was tested. The wear results were compared to Amalgam as reference material. It should be computed whether there exists a correlation between the wear results of resin composite and matrix alone. Wear of the veneering composites was significantly higher than of Z100 (13 μm) and Amalgam (14 μm; p < 0.01, Mann‐Whitney U‐test). Mean fracture strengths of indirect composites ranged from 127.5 MPa (Targis) to 71.6 MPa (Vita Zeta LC). The elastic moduli of the composites were between 2.9 and 12.8 GPa. The matrix wear rates did not differ significantly. Three‐body wear results of complex resin composites are highly influenced by their filler content, filler particle size distribution, kind of filler particles, shape, and their silanization to the matrix. Due to this fact, three‐body wear testing is an essential testing method and cannot be replaced by testing single material components. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 65–69, 2004
Control of cell adhesion and detachment using temperature and thermoresponsive copolymer grafted culture surfaces
Authors: Tsuda Yukiko , Kikuchi Akihiko , Yamato Masayuki , Sakurai Yasuhisa , Umezu Mitsuo , Okano Teruo
Published: March 2004

The hydrophobic monomer, n‐butyl methacrylate (BMA) has been incorporated into thermoresponsive poly(N‐isopropylacrylamide) (PIPAAm) to lower PIPAAm phase transition temperatures necessary for systematically regulating cell adhesion on and detachment from culture dishes at controlled temperatures. Poly(IPAAm‐co‐BMA)‐grafted dishes were prepared by electron beam irradiation methods, systematically changing BMA content in the feed. Copolymer‐grafted surfaces decreased grafted polymer transition temperatures with increasing BMA content as shown by water wettabilities compared to homopolymer PIPAAm‐grafted surfaces. Bovine endothelial cells readily adhered and proliferated on copolymer‐grafted surfaces above collapse temperature at 37°C, finally reaching confluence. Cell sheet detachment behavior from copolymer‐grafted surfaces depended on the culture temperature and BMA content. In conclusion, cell attachment/detachment can be controlled to an arbitrary temperature by varying the content of hydrophobic monomer incorporated into PIPAAm grafted to culture surfaces. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 70–78, 2004
Delayed fracture of Ni‐Ti superelastic alloys in acidic and neutral fluoride solutions
Authors: Yokoyama Ken'ichi , Kaneko Kazuyuki , Moriyama Keiji , Asaoka Kenzo , Sakai Jun'ichi , Nagumo Michihiko
Published: March 2004

Hydrogen‐related degradation of the mechanical properties of a Ni‐Ti superelastic alloy has been examined by means of delayed fracture tests in acidic and neutral fluoride solutions and hydrogen thermal desorption analysis. Delayed fracture took place in both solutions; the time to fracture was shorter in the acidic solutions than in the neutral solutions with the same fluoride concentration. The time to fracture was reduced in both solutions when applied stress exceeded the critical stress for martensite transformation. In the acidic solutions, Ni‐Ti superelastic alloy underwent general corrosion and absorbed substantial amounts of hydrogen. Fractographic features suggested that the delayed fracture in the acidic solutions was attributable to hydrogen embrittlement, whereas in the neutral solutions, a different fracture mode appeared associated with localized corrosion only in the vicinity of the fracture initiation area. In the neutral solutions, the amount of absorbed hydrogen was much less than that in the acidic solutions, and the delayed fracture was likely to be induced by active path corrosion accompanying hydrogen absorption. The results of the present study imply that the hydrogen‐related degradation of performance of Ni‐Ti superelastic alloys occurs in the presence of fluoride. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 105–113, 2004
Stretch‐mediated responses of osteoblast‐like cells cultured on titanium‐coated substrates in vitro
Authors: Walboomers X. F. , Habraken W. J. E. M. , Feddes B. , Winter L. C. , Bumgardner J. D. , Jansen J. A.
Published: March 2004

Cyclic stretching experiments on osteoblast‐like cells have proven to be a useful tool in understanding the underlying mechanisms of load transduction at the bone–implant surface. However, most experimental setups use silicone rubber substrates, which are atypical for orthopedic and dental implant materials. Therefore, we investigated the responses of osteoblast‐like cells to loading on titanium (Ti)‐coated versus plain silicone substrates. Ti‐coated substrates were made by a radio‐frequency magnetron sputtering process, and characterized using Rutherford backscattering spectrometry, X‐ray photoelectron spectroscopy, and contact‐angle measurements. Osteoblast‐like cells cultured from rat bone marrow were seeded on both types of substrates and stretched for 1 h continuously. Subsequently, cell proliferation, alkaline phosphatase activity, and calcium content were measured for up to 24 days after seeding. In addition light‐, scanning electron‐, and confocal laser scanning micrographs were made. The results showed that our Ti coating had a thickness of 50 nm and contained Ti/oxygen as 1:1. However, further characterization proved that the silicone material had a tendency to resurface through the coating. Osteoblast‐like cells proliferated faster on the Ti‐coated substrates, but differentiation was slower compared with the silicone substrates. It was concluded that that there was a definitive influence of the substrate material in mechanical stress models. Therefore, extrapolation of results obtained using silicone substrates cannot be translated directly toward the situation of metallic implant materials. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 131–139, 2004
Apparent viscoelastic anisotropy as measured from nondestructive oscillatory tests can reflect the presence of a flaw in cortical bone
Authors: Yeni Yener N. , Christopherson Gregory T. , Turner A. Simon , Les Clifford M. , Fyhrie David P.
Published: March 2004

There is evidence that damage, viscoelastic stiffness properties, and postyield mechanical properties are related in bone tissue. Our objective was to test whether presence of a flaw would have an influence on the apparent viscoelastic properties of bone. Examining the effect of flaw orientation on apparent viscoelastic properties and utilization of dynamic mechanical analysis (DMA) as a nondestructive means for detection of damage were our secondary objectives. Cortical bone beams (2 × 2 × 19 mm) machined from the cranial cortex of the radii of six Warhill sheep were used. The specimens were placed in a DMA machine and baseline measurements of storage modulus (E1) and loss factor (tan δ), once for loads in the craniocaudal and once in the mediolateral directions, were performed using a three‐point bending configuration for a frequency range of 1–10 Hz. Craniocaudal/mediolateral measurement ratio was calculated as a measure of anisotropy for tan δ and E1. After cutting a thin through‐thickness macroscopic notch on the caudal surface at the center of each beam, oscillatory tests were repeated. Two‐way repeated measures analysis of variance followed by Tukey's test was used with group (craniocaudal, mediolateral, notched craniocaudal, and notched mediolateral measurements) and frequency as factors. Regression analysis and analysis of covariance were used for examining the relationship between viscoelastic parameters and frequency. Tan δ and E1 were not different between craniocaudal and mediolateral measurements before the flaw was introduced (p > 0.8 and p = 1, respectively). In the presence of the flaw, tan δ was significantly increased (p < 0.003) whereas E1 was significantly reduced (p < 0.001) for craniocaudal measurements. Tan δ and E1 were nearly isotropic in the tested directions before the introduction of a flaw into the bone tissue. Introduction of a flaw resulted in increased tan δ and E1 anisotropy. Presence of a notch resulted in a significant increase in tan δ anisotropy with increasing frequency. In conclusion, we have demonstrated that cortical bone tissue exhibits a different apparent viscoelastic behavior in the presence of a flaw and depending on the flaw's orientation. Our finding that the presence of a notch and its orientation can be detected by nondestructive DMA suggests that in vivo techniques may be developed for detection of cortical bone damage. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 124–130, 2004
BETWEEN TWO CULTURES: A CONVERSATION WITH SHULAMIT RAN
Authors: Miller Malcolm
Published: March 2004

Although Israeli performers are widely recognized in the international arena, serious music composed by Israeli composers is far less well known. Yet, throughout Israel's 55-year history to date, contemporary music has attained a remarkably dynamic, thriving impetus despite (and perhaps partly as a consequence of) the harsh realities of daily life. The works of four generations (and a rising fifth generation) of composers in all genres and instrumental combinations may still be known far less than they deserve across the world, yet the amount of new recordings, published studies and performances is encouraging evidence of increasing interest. This article-interview is intended to deepen appreciation of an important repertoire through an introduction to the music and ideas of one of the foremost Israeli composers, the Chicago-based Shulamit Ran, whose unique outlook is influenced by two cultures, those of Israel and America.
A correction
Authors: McCALL SMITH JAMES
Published: March 2004

In my article ‘WTO Dispute Settlement: the Politics of Procedure in Appellate body Rulings’ (March 2003), I linked the resignation of Debra Steger, former Director of the Appellate Body Secretariat, to the political controversy regarding amicus curiae submissions. This erroneous conclusion was based on two interviews in Geneva and implicitly supportive evidence from a WTO Reporter article.
The BAR‐domain family of proteins: a case of bending and binding?
Authors: Habermann Bianca
Published: March 2004

BAR‐domains recently took centre stage in science through a report on the crystal structure of this domain in Drosophila Amphiphysin. Though only weakly conserved at the sequence level, the structure of the BAR domain shows striking similarity to the GTPase‐binding domain of Arfaptin 2, an effector of Rho‐ and Arf‐ GTPases. On the basis of this sequence and structural similarity, these two proteins have been classified as belonging to the same family, the BAR‐domain family, and they probably also have similar functional characteristics. Presented here are the results of a database search for the sequence of the BAR domain of Amphiphysin and Arfaptin 2. This search identified a variety of related proteins, most of which are involved in intracellular transport and especially in endocytosis. For example, the BAR‐domain family includes Endophilins, GTPase‐activating proteins of the Centaurinβ family and Oligophrenins, the adaptor proteins APPL1 and APPL2 that were recently shown to interact with the small GTPase Rab5, as well as members of the Sorting nexin family. On the basis of the structures of Amphiphysin and Arfaptin 2 and the cellular role of Amphiphysins in the early steps of endocytosis, the functions of the BAR domain have been defined as a dimerization motif and as sensing and inducing membrane curvature. However, data on Arfaptin 2 and now also on the Adaptor proteins APPL1 and 2 suggest that another function of the BAR domain is to bind to small GTPases.
Whole Genome Sequence Comparisons and “Full-Length” cDNA Sequences: A Combined Approach to Evaluate and Improve Arabidopsis Genome Annotation
Authors: Castelli Vanina , Aury Jean-Marc , Jaillon Olivier , Wincker Patrick , Clepet Christian , Menard Manuella , Cruaud Corinne , Quétier Francis , Scarpelli Claude , Schächter Vincent , Temple Gary , Caboche Michel , Weissenbach Jean , Salanoubat Marcel
Published: March 2004

To evaluate the existing annotation of the Arabidopsis genome further, we generated a collection of evolutionary conserved regions (ecores) between Arabidopsis and rice. The ecore analysis provides evidence that the gene catalog of Arabidopsis is not yet complete, and that a number of these annotations require re-examination. To improve the Arabidopsis genome annotation further, we used a novel “full-length” enriched cDNA collection prepared from several tissues. An additional 1931 genes were covered by new “full-length” cDNA sequences, raising the number of annotated genes with a corresponding “full-length” cDNA sequence to about 14,000. Detailed comparisons between these “full-length” cDNA sequences and annotated genes show that this resource is very helpful in determining the correct structure of genes, in particular, those not yet supported by “full-length” cDNAs. In addition, a total of 326 genomic regions not included previously in the Arabidopsis genome annotation were detected by this cDNA resource, providing clues for new gene discovery. Because, as expected, the two data sets only partially overlap, their combination produces very useful information for improving the Arabidopsis genome annotation.
Comparative Analysis of Protein Domain Organization
Authors: Ye Yuzhen , Godzik Adam
Published: March 2004

We have developed a set of graph theory-based tools, which we call Comparative Analysis of Protein Domain Organization (CADO), to survey and compare protein domain organizations of different organisms. In the language of CADO, the organization of protein domains in a given organism is shown as a domain graph in which protein domains are represented as vertices, and domain combinations, defined as instances of two domains found in one protein, are represented as edges. CADO provides a new way to analyze and compare whole proteomes, including identifying the consensus and difference of domain organization between organisms. CADO was used to analyze and compare >50 bacterial, archaeal, and eukaryotic genomes. Examples and overviews presented here include the analysis of the modularity of domain graphs and the functional study of domains based on the graph topology. We also report on the results of comparing domain graphs of two organisms,Pyrococcus horikoshii(an extremophile) andHaemophilus influenzae(a parasite with reduced genome) with other organisms. Our comparison provides new insights into the genome organization of these organisms. Finally, we report on the specific domain combinations characterizing the three kingdoms of life, and the kingdom “signature” domain organizations derived from those specific domain combinations.
Quantifying Modularity in the Evolution of Biomolecular Systems
Authors: Snel Berend , Huynen Martijn A.
Published: March 2004

Functional modules are considered the primary building blocks of biomolecular systems. Here we study to what extent functional modules behave cohesively across genomes:That is, are functional modules also evolutionary modules? We probe this question by analyzing for a large collection of functional modules the phyletic patterns of their genes across 110 genomes. The majority of functional modules display limited evolutionary modularity. This result confirms certain comparative genome analyses, but is in contrast to implicit assumptions in the systems analysis of functional genomics data. We show that this apparent interspecies flexibility in the organization of functional modules depends more on functional differentiation within orthologous groups of genes, than on noise in the functional module definitions. When filtering out these sources of nonmodularity, even though very few functional modules behave perfectly modular in evolution, about half behave at least significantly more modular than a random set of genes. There are substantial differences in the evolutionary modularity between individual functional modules as well as between collections of functional modules, partly corresponding to conceptual differences in the functional module definition, which make comparisons between functional module collections biologically difficult to interpret. Analysis within one collection does not suffer from such differences, and we show that within the EcoCyc metabolic pathway database, biosynthetic pathways are evolutionarily more modular than catabolic pathways.
Parallel Genotyping of Over 10,000 SNPs Using a One-Primer Assay on a High-Density Oligonucleotide Array
Authors: Matsuzaki Hajime , Loi Halina , Dong Shoulian , Tsai Ya-Yu , Fang Joy , Law Jane , Di Xiaojun , Liu Wei-Min , Yang Geoffrey , Liu Guoying , Huang Jing , Kennedy Giulia C. , Ryder Thomas B. , Marcus Gregory A. , Walsh P. Sean , Shriver Mark D. , Puck Jennifer M. , Jones Keith W. , Mei Rui
Published: March 2004

The analysis of single nucleotide polymorphisms (SNPs) is increasingly utilizedto investigate the genetic causes of complex human diseases. Here we present a high-throughput genotyping platform that uses a one-primer assay to genotype over 10,000 SNPs per individual on a single oligonucleotide array. This approach uses restriction digestion to fractionate the genome, followed by amplification of a specific fractionated subset of the genome. The resulting reduction in genome complexity enables allele-specific hybridization to the array. The selection of SNPs was primarily determined by computer-predicted lengths of restriction fragments containing the SNPs, andwas further driven by strict empirical measurements of accuracy, reproducibility, andaverage call rate, which we estimate to be >9.5%, >99.9%, and>95%, respectively. With average heterozygosity of 0.38 andgenome scan resolution of 0.31 cM, the SNP array is a viable alternative to panels of microsatellites (STRs). As a demonstration of the utility of the genotyping platform in whole-genome scans, we have replicated and refined a linkage region on chromosome 2p for chronic mucocutaneous candidiasis and thyroid disease, previously identified using a panel of microsatellite (STR) markers.
zPicture: Dynamic Alignment and Visualization Tool for Analyzing Conservation Profiles
Authors: Ovcharenko Ivan , Loots Gabriela G. , Hardison Ross C. , Miller Webb , Stubbs Lisa
Published: March 2004

Comparative sequence analysis has evolved as an essential technique for identifying functional coding and noncoding elements conserved throughout evolution. Here, we introduce zPicture, an interactive Web-based sequence alignment and visualization tool for dynamically generating conservation profiles and identifying evolutionarily conserved regions (ECRs). zPicture is highly flexible, because critical parameters can be modified interactively, allowing users to differentially predict ECRs in comparisons of sequences of different phylogenetic distances and evolutionary rates. We demonstrate the application of this module to identify a known regulatory element in the HOXD locus, in which functional ECRs are difficult to discern against the highly conserved genomic background. zPicture also facilitates transcription factor binding-site analysis via the rVista tool portal. We present an example of the HBB complex when zPicture/rVista combination specifically pinpoints to two ECRs containing GATA-1, NF-E2, and TAL1/E47 binding sites that were identified previously as transcriptional enhancers. In addition, zPicture is linked to the UCSC Genome Browser, allowing users to automatically extract sequences and gene annotations for any recorded locus. Finally, we describe howthis tool can be efficiently applied to the analysis of nonvertebrate genomes, including those of microbial organisms.
Towards a knowledge‐sharing scaffolding environment based on learners’ questions
Authors: Ng’ambi Dick , Hardman Joanne
Published: March 2004

This article describes a web‐based communicative space (a Dynamic Frequently Asked Questions environment—DFAQ) in which learners consult one another using questions, and in which both the flow of interaction and its artefacts become a resource available to a community of learners. Anecdotal evidence suggests that learners embarking on their first year of university study enter a world that is essentially text‐based and are inclined to view text as an authority, as something fixed that closes rather than opens up enquiry. Motivated by the need to scaffold learners’ engagement with academic text, we developed the DFAQ in which learners asked questions and other learners responded. The article discusses the learning activity that led to student consultation and provides a critical review of the environment based on student interviews. Our conclusion is that the environment provides learners with a unique ‘space’ in which to access questions and responses that they might not have generated themselves. Furthermore, given the environment's capacity to recruit, hold and focus attention as well as model appropriate questioning behaviour, we think that it does indeed provide a space that scaffolds learners’ engagement with the text.
From peripheral to full participation in a blended trade bargaining simulation
Authors: Carr Tony , Cox Lenda , Eden Ndrea , Hanslo Monique
Published: March 2004

This article considers the extent and nature of student participation in a trade bargaining simulation from a community of practice perspective. This third‐year economics module included a blend of online communication (through email, online chats and online discussions) and face‐to‐face meetings, both in smaller bargaining groups and in whole class plenary meetings. Our method of analysis includes the use of Exchange Structure Analysis of text chats and face‐to‐face learning conversations, triangulated by observation, survey and interview data. The focus on community of practice enables us to offer a nuanced interpretation of differences in crude participation data derived from the online chats. Superficially, the data may suggest marginalisation of participants, but Wenger's (1988) notion of peripheral participation with a trajectory towards full participation reframes the disparities in terms of an active community of practice. Some members are fully engaged with the practices of trade bargaining from the early stages of the simulation, while others move towards full participation over the duration of the simulation. Our results suggest that the laboratory‐based online text chats did provide opportunities for student participation in the simulation, and that male and female students exhibited different patterns of participation in the chats.
Demography of fluctuating populations: temporal and phase‐related changes in vital rates of Microtus ochrogaster
Authors: Ozgul Arpat , Getz Lowell L. , Oli Madan K.
Published: March 2004

Small mammal population fluctuations, cyclic or not, have been an ecological puzzle and a source of heated debate among ecologists. Identifying the demographic parameters that covary closely with density changes can help elucidate the underlying causes of population fluctuations, but few studies have reported rigorous estimates of these parameters.

We applied capture–mark–recapture analysis to twice‐weekly trapping data from a long‐term study of a fluctuating Microtus ochrogaster (prairie vole) population in Illinois, USA to estimate stage‐specific apparent survival and maturation rates. We also estimated population density, fecundity rate, age at maturity and life span on a weekly basis.

Survival, maturation and fecundity rates exhibited phase‐related changes during major density fluctuations, but they showed density‐independent temporal variations during the prolonged low‐density phases. Among these variables, maturation and juvenile survival rates covaried most closely with population density.

These results suggest that phase‐related changes in maturation and juvenile survival rates are likely to be the main demographic factors driving the dynamics of our study population.

Phase‐related changes in maturation rates provide a plausible demographic explanation of density fluctuations in our study population. Our results suggest that direct predation may not be necessary for large‐scale fluctuations in M. ochrogaster abundance.
Life history and fitness consequences of ectoparasites
Authors: Fitze Patrick S. , Tschirren Barbara , Richner Heinz
Published: March 2004

For iteroparous organisms life‐history theory predicts a trade‐off between current and future reproduction, and therefore the evolution of host responses to current parasite infestation that will maximize lifetime reproductive success. The parasite‐induced variation in reproductive success is thus not the net result of parasite infestation alone, but the parasite‐mediated outcome of optimal resource allocation among current and future reproductive events. Understanding the importance of parasites for the evolution of host life history therefore requires an experimental investigation of the effects of parasites over the host's life span. Such studies are currently scant.

We manipulated the load of an ectoparasite, the hen flea (Ceratophyllus gallinae), in the nests of its most common host, the great tit (Parus major), over a period of 4 years and recorded, the components of current and future reproductive success including survival, divorce, breeding dispersal and various reproductive parameters. Finally we assessed, for females only as paternity of males was unknown, the lifetime reproductive success as a close correlate of Darwinian fitness.

For current reproduction, our experiment demonstrates that parasites reduce current reproductive success via an increase in the probability of nest failure during incubation and the nestling period. In the presence of fleas, clutch size and the number of fledglings were reduced while the incubation and the nestling period were prolonged. Thus parasitism led to an increase in parental effort but nevertheless reduced current reproductive success.

For future reproduction, the experiment shows that females breeding in infested nests dispersed over longer distances between breeding attempts. The divorce rate following infestation, the probability of breeding locally in the future and residual reproductive success were not affected significantly by ectoparasites. The study thus suggests that hen fleas play a minor role in shaping the trade‐off between current and future reproduction.

Lifetime reproductive success of females, measured as the total number of locally recruiting offspring over the 4 experimental years, was reduced significantly by ectoparasites. The negative effect of parasites arose by a reduction of the number of fledglings per breeding attempt rather than by a reduction of the number of breeding attempts.
Altitudinal variation in the relationship between growth and maturation rate in salmon parr
Authors: Baum Diane , Laughton Robert , Armstrong John D. , Metcalfe Neil B.
Published: March 2004

It is well established that the likelihood of an individual animal becoming mature is influenced strongly by its previous growth. However, with few exceptions, it is not known whether common relationships between the two parameters apply within and among populations.

Using data collected from tributaries of a single river, we investigate the relationship between size and maturation in Atlantic salmon parr, and whether spatial variation in the incidence of parr maturation can be explained by variation in growth rates.

There was spatial variation in the size of parr, a large proportion of which was attributable to altitude. However, this did not explain the variation between sites in the maturation rate of parr. In contrast to earlier findings, there was no relationship between the mean size of parr at a site and the percentage of males that matured there for the age class in which most mature males were found.

Within a site size at age was a good predictor of maturation, but across sites this relationship was modified by altitude. For a given age and size a parr was more likely to become sexually mature if it came from a high‐altitude site.

Spatial variation in the incidence of male parr maturity is not simply the result of variation in growth rates. The size threshold above which parr male parr matured depended on altitude, which could serve as a proxy for growth opportunity.

We suggest adaptive explanations for variation in the relationship between growth and maturation, particularly the importance of relative, as opposed to absolute body size.

Our study suggests a high level of complexity in the proximate mechanisms governing life‐history strategies in order to bring about adaptive strategy choice.
Generalized linear models for means and variances applied to movement of tiger beetles along corridor roads
Authors: Van Dooren Tom J. M. , Matthysen E.
Published: March 2004

Movement is often conditional on environmental parameters and behavioural phenotype. A reasonable assumption is that individuals behave as random walkers, when environment and behaviour are fixed.

Based on this assumption, observations of movements can be analysed with a set of generalized linear models. Such models can predict the occurrence of behaviour and movement distance distributions resulting from different behavioural or environmental parameters.

This method was applied to study short‐range movement of tiger beetles (Cicindela hybrida) along corridor roads.

Logistic regression was used to estimate probabilities of behaviour types occurring during 5‐min observation intervals.

Movement distances were investigated with a pair of generalized regression models for both the mean and the variance of the distances covered during observations. The models estimate mean and variance of a normal distribution per set of environmental conditions and per combination of behaviour types observed in the observation interval.

Flying behaviour, the number of interactions with other beetles and the amount of food items handled differed between spring and summer season.

Advective movement was demonstrated, and it occurred in the direction of the sun. The advection effect is more pronounced when beetles fly. We propose that this advection occurs as a side effect of thermoregulatory behaviour.

Diffusion or spread of displacements increased with the occurrence of flying and decreased when beetles spent time sheltering in shade or handling food.

Simulations were used to generate movement distributions over longer time spans, assuming that the selected model applies per time step. Such distributions can be used to generate null hypotheses for different types of experiments, and for extrapolation.

The simulations show that only when there is little advection do distance distributions remain normal. Mean predicted displacement distances reach up to around 100 meter after 2 h.
Contrasting dynamics in two subpopulations of a leech metapopulation over 25 year‐classes in a small stream
Authors: Elliott J. M.
Published: March 2004

The leech,Erpobdella octoculata(L.), occurred as two local populations at sites A (deep section with macrophytes) and B (shallow stony section) in a small stream. A June census estimated densities of young leeches (R1 m−2) and mature leeches (R2 m−2) towards the end of the first and second years of the life cycle, respectively. An August census estimated the density of cocoons laid by the mature leeches before they died in autumn. Cocoon density multiplied by the mean number of young per cocoon estimated the density of young produced at the end of each year‐class (R3 m−2) and also the density at the start of the next year‐class (Sm−2). Information was obtained for 25 year‐classes (1966–90).

The spatial distribution of the leeches and their cocoons was aggregated and similar at both sites in spite of the marked differences in habitat. Survivor density at three life stages (R1,R2,R3) was related to the density of young at the start of each year‐class (S), the density‐dependent relationship being described by a dome‐shaped Ricker curve that differed markedly between sites. A few year‐classes were excluded from the analyses because their density was reduced by a severe spate and three summer droughts. A stability analysis showed that the subpopulation at site A was essentially stable around the equilibrium density, whereas that at site B was strongly cyclic and was approaching chaotic behaviour.

Loss‐rates were fairly constant in the second year of the life cycle, but those in the first year were very variable and related positively to the density of mature leeches. The latter ate newly hatched leeches, even those still in cocoons. Cannibalism appeared to be the most obvious mechanism responsible for the density‐dependent relationships, its impact being greatest at site B. Loss‐rates were not dependent on the density of the young leeches themselves (i.e. direct density dependence) but on the density of mature leeches that ate them (i.e. delayed density dependence). This case study illustrates how subpopulations in a metapopulation can have both similar (spatial distribution) and contrasting (density fluctuations) dynamics.
Seasonal dynamics of mycoplasmal conjunctivitis in eastern North American house finches
Authors: Altizer Sonia , Hochachka Wesley M. , Dhondt André A.
Published: March 2004

Mycoplasma gallisepticumis an emerging eye disease that spread rapidly among wild house finches (Carpodacus mexicanus) in the eastern United States following initial reports of infected birds in 1994. The hallmark signs of infection have allowed systematic monitoring of disease at both local and continent‐wide scales for more than 7 years since the onset of the epidemic.

Using data collected by a network of citizen science volunteers, we examined both long‐term trends and seasonal dynamics of mycoplasmal conjunctivitis in three different climatic regions in eastern North America over a 77‐month period (November 1994–March 2001).

Time‐series prevalence data from all three regions suggest that following establishment, marked seasonal fluctuations in prevalence each year were characterized by autumn–winter epidemics (in October and February) and consistent summer declines (with prevalence falling close to zero from May to July).

The maximum peak, annual rates of increase and timing of epidemics varied among three geographical locations that were delineated by minimum winter temperatures. Annual autumn prevalence in the South increased more rapidly, and maximum prevalence was nearly three times greater in the South than in the colder North and Central regions.

Longer‐term trends showed evidence for multiyear fluctuations in prevalence that were characterized by greater amplitude in the southern region.

Finally, monthly estimates of house finch flock sizes derived from a similar citizen science data set showed that winter flock sizes were associated positively with average monthly prevalence in the northern and central regions, although regional differences in flock sizes did not correspond to regional differences in maximum prevalence.

This study represents the first evidence of multiyear fluctuations, regional differences and highly predictable annual outbreaks of this recently emerged wildlife pathogen. Several factors associated with house finch life history and behaviour are likely to contribute to temporal and spatial variation in prevalence, including annual changes in host reproduction, social behaviour and environmental effects on host stress or immunocompetence.
Emerging associations on marine rocky shores: specialist herbivores on introduced macroalgae
Authors: Trowbridge Cynthia D.
Published: March 2004

Sacoglossan sea slugs (Gastropoda: Opisthobranchia) can change their highly specialized algal host associations in response to introduced hosts.

Adult sacoglossans (Placida dendritica) collected from the introduced green macroalga Codium fragile ssp. tomentosoides in west‐coast Scottish sea lochs tended to associate with and consume introduced hosts over the native C. tomentosum in pairwise‐choice feeding trials.

On west‐coast Irish shores, where native congeneric hosts were more common, significantly more P. dendritica attacked C. tomentosum on the shore whereas Elysia viridis disproportionately attacked the exotics. In Lough Hyne, Co. Cork, Ireland, juvenile E. viridis attacked both C. fragile ssp. tomentosoides and the native, sympatric C. vermilara; in pairwise‐choice feeding trials, sacoglossans preferred the host species from which they were collected.

In the Channel Islands, adult E. viridis were common on C. tomentosum on Guernsey shores. In pairwise‐choice feeding trials adults exhibited no preference between native and introduced hosts, indicating that the stenophagous herbivores could change their associations.

On temperate Australian shores, the native sacoglossan Placida aoteana attacked the recently introduced C. fragile ssp. tomentosoides as well as native congeners and conspecifics. P. aoteana was common and its herbivory evident in Victoria and Tasmania. Slugs collected from native C. fragile exhibited no preference between algal subspecies in Victoria but a strong preference for the introduced subspecies in Tasmania.

Flexibility in host use enables stenophagous marine herbivores to respond within years to the presence of recently introduced hosts. The implicit peril of the host‐specificity paradigm − that specialists could change their associations − does occur in stenophagous sacoglossans, and there is considerable intra‐ and interspecific variation in response.

Biological control of invasive green algae using sacoglossan herbivores is fraught with several risks, including taxonomic uncertainty of species’ boundaries, ecological flexibility of feeding, unexplored role of host susceptibility and insufficient evolutionary–developmental information to establish coevolutionary associations.
Low‐temperature‐driven early spawning migration of a temperate marine fish
Authors: Sims David W. , Wearmouth Victoria J. , Genner Martin J. , Southward Alan J. , Hawkins Stephen J.
Published: March 2004

It is often assumed that the timing of annual migrations of marine fish to spawning grounds occurs with very little change over time. However, it is unclear how much migration is influenced by climate change in marine species that spawn at sea but spend most time in estuarine conditions, especially as thermal regimes in estuaries may differ significantly from those in the open sea.

Migration phenology was studied in a population of flounder, Platichthys flesus (L.) off south‐west England using high‐temporal resolution trawling data over a 13‐year period.

Flounder migrated from their estuarine habitat to spawning grounds at sea some 1–2 months earlier in years that were up to 2 °C cooler. Flounder arrived on the spawning grounds over a shorter time period (2–6 days) when colder than normal conditions prevailed in the estuary, compared to warmer years (12–15 days). This suggests that they were responding to low temperatures by exhibiting a more synchronous, population‐level early migration.

The timing of migration was earlier when the largest differences in temperatures between near‐estuary and offshore environments occurred, differences that were related significantly to cold, negative phases of the North Atlantic Oscillation (NAO).

Flounder migration phenology appears to be driven to a large extent by short‐term, climate‐induced changes in the thermal resources of their overwintering habitat. This suggests that climate fluctuations characterizing the NAO may have significant effects on the timing of the peak abundance of fish populations generally, which, in turn, may have implications for fisheries management.
Year‐ and sex‐dependent effects of experimental brood sex ratio manipulation on fledging condition of Eurasian kestrels
Authors: Laaksonen Toni , Fargallo Juan A. , Korpimäki Erkki , Lyytinen Sami , Valkama Jari , Pöyri Ville
Published: March 2004

Offspring sex ratio may be an unpredictable component of life history that might select for behavioural plasticity in parental care. If the parents do not have such plasticity and the two sexes of offspring differ in size, individuals in a brood or litter biased towards the larger sex offspring may suffer from food shortage. Sibling sex ratio could also affect the young through asymmetric sex‐related sibling competition.

We created single‐sex broods of sexually size‐dimorphic Eurasian kestrels (Falco tinnunculusL.) with mixed‐sex control broods in order to test whether parents have behavioural plasticity to respond to the sex ratio of their brood and whether smaller male chicks suffer from reduced health status because their larger female siblings outrival them in sibling competition. The experiment was conducted during two years (2000 and 2001) that differed in the abundance of voles, the main natural prey of kestrels.

No obvious effects of the brood sex ratio manipulation on parental effort were detected, as there were no differences in prey delivery rate, biomass of prey brought to the nest, body mass or heterophile/lymphocyte ratio of the parents.

Female chicks in all‐female broods had lower haematocrit levels than those in mixed‐sex broods in a year of low vole abundance. As haematocrit is an index of nutritional condition and health state, this result indicates that in the year of low vole abundance the female chicks in all‐female broods fledged in poorer condition than those in mixed‐sex broods.

These results indicate that when the parents do not alter their level of parental effort in response to the sex ratio of their brood, the young in a brood biased towards the larger sex offspring can be reared successfully when food is abundant, while they may suffer under food shortage situations.

Kestrel chicks of both sexes had low haematocrit levels and T cell‐mediated immune responses in the year of low vole abundance. This result indicates that poor health state at fledging may provide a causal link for low recruitment of kestrels hatched in years of low vole abundance.
Competition for breeding sites and site‐dependent population regulation in a highly colonial seabird, the common guillemot Uria aalge
Authors: Kokko Hanna , Harris Michael P. , Wanless Sarah
Published: March 2004

The hypothesis of site‐dependent population regulation predicts that birds utilize available nesting sites in a pre‐emptive (ideal despotic) manner, leading to density dependence in heterogeneous habitats as poorer sites are used at higher population densities. At small population sizes adaptive site choice protects populations against fluctuations (the buffer effect).

Common guillemots Uria aalge (Pontoppidan) breed at high density on sea‐cliffs. The population breeding on the Isle of May, Scotland increased by 60% between 1981 and 2000. A good nest‐site is a prerequisite for successful breeding and there is much competition for the best sites. Throughout this period, site use correlated with two measures of site quality, and photographs taken in 1936 show that this pattern has been extremely stable.

The data indicate declining quality of sites that remain available as the population has increased. Site‐dependent regulation was evident in that average breeding success declined over the years, but no declining trend was detected in the best (and most preferred) sites.

An individual guillemot generally uses the same nest‐site from year to year, but a minority move, usually less than 2 m, between breeding seasons. These movements can be involuntary or voluntary. Involuntarily moving birds that had occupied very good sites before moving often spent several years as non‐breeders (floaters) close to their previous site before breeding again, and then occupied poorer sites. Voluntarily moving birds significantly improved their site quality by moving.

Birds responded both to the physical site characteristics and to their own experience (breeding failure) when abandoning a site. Their behaviour thus combined aspects of the ‘win‐stay, lose‐switch’ strategy with direct assessment of site quality. Our data set is inconclusive with respect to the public information hypothesis, i.e. whether birds use conspecific cues of breeding success when settling in a new site.
Endodontic treatment of dens invaginatus type III with three root canals and open apical foramen
Authors: Jung M.
Published: March 2004

Aim  To describe the conservative endodontic treatment and the 1‐year follow‐up of a permanent maxillary lateral incisor with dens invaginatus.

Summary  Frequently, the root canal treatment of invaginated teeth is challenging because of problems associated with gaining access to the root canals and with variations of canal morphology associated with this type of malformation. The present case describes the complex root canal treatment of dens invaginatus in a maxillary lateral incisor with three root canals (Oehler type III), incomplete apex formation, necrotic pulp and abscess formation. After gaining access to two root canals and the invagination with the help of a dental operating‐microscope, the canals and the invagination were instrumented and calcium hydroxide dressing was applied for 6 months. Apexification and osseous bone repair were achieved, and the canals were filled with gutta‐percha. A follow‐up after 1 year showed that the tooth was free of any clinical symptoms and the periapical condition was normal.

Key learning points 

The present case demonstrates that conservative root canal treatment can be performed successfully even in severe cases of dens invaginatus.

The use of a dental operating microscope can help in the management of complicated cases of invaginated teeth through conventional root canal treatment.
Role of substance P and calcitonin gene‐related peptide in the regulation of interleukin‐8 and monocyte chemotactic protein‐1 expression in human dental pulp
Authors: Park S. H. , Hsiao G. Y.‐W. , Huang G. T.‐J.
Published: March 2004

Aim  To determine whether leucocyte infiltration during neurogenic inflammation in the pulp is regulated by neuropeptides via inducing the release of proinflammatory chemokines interleukin‐8 (IL‐8) and monocyte chemotactic protein‐1 (MCP‐1) from human dental pulp.

Methodology  Cultured primary pulp cells and pulp tissue explants were stimulated with substance P (SP) and/or calcitonin gene‐related peptide (CGRP). IL‐8 or MCP‐1, secreted from cultured cells or produced in pulp explants, was analysed by enzyme‐linked immunosorbent assay.

Results  Substance P induced IL‐8 secretion from cultured pulp cells (approximately threefold increase over control, P < 0.05) and from pulp tissue explants (two‐ to three fold). SP only minimally to moderately induced MCP‐1 (approximately two fold) in cultured pulp cells. While MCP‐1 induction in cultured pulp cells was detected after 24 h of SP stimulation, no induction was observed in pulp tissue. CGRP did not induce IL‐8, but moderately increased MCP‐1 production (approximately three fold) in cultured pulp cells. There was no synergistic induction of MCP‐1 by SP plus CGRP stimulation of pulp cells.

Conclusions  Substance P is a stronger inducer of IL‐8 production in dental pulp than CGRP. IL‐8 is more strongly induced than MCP‐1 by SP, suggesting a more important role for IL‐8 than MCP‐1 in leucocyte infiltration during neurogenic inflammation in dental pulp.