bluuebunny/crossref_metadata_2025 huggingface dataset:
Floating mats: their occurrence and influence on shoreline distribution of emergent vegetation
Authors: AZZA NICHOLAS , DENNY PATRICK , VAN DE KOPPEL JOHAN , KANSIIME FRANK
Published: June 2006

1. A study was conducted on the northern shore of Lake Victoria (Uganda) to determine the factors controlling the occurrence of floating root mats and the influence of the floating mats on the distribution of emergent vegetation.

2. Environmental conditions within 78 bays in the study area were characterised using bay size, wave exposure, water depth, littoral slope, sediment characteristics and water level fluctuations. Emergent plants that form floating root mats occur along the shores of these bays. The way in which commonly occurring shoreline vegetation was distributed across a wave‐exposure gradient was compared with their distribution across a water level fluctuation gradient.

3. Results suggested that wind–wave action and water level fluctuations are important factors determining the occurrence of floating mats. Mat‐forming plants occur in the most sheltered locations along the shore and in waterbodies with modest water level fluctuations.

4. The ability to form mats facilitated the lakeward expansion of emergent plants. Plants forming floating root mats had a larger depth range than non‐mat forming plants.

5. The initiation mechanisms for the floating mats of emergent vegetation in Lake Victoria appear to be: (i) invasion of mats of free‐floating plants by emergent vegetation; and (ii) detachment of emergent plants from the lake bed following flooding.

6. The formation of floating mats comes with a cost and benefit to emergent plants. The cost is increased vulnerability to damage by water level fluctuations or wind–wave action, leading to reduced horizontal distribution. The benefit is that deep flooding is avoided, thus increasing vertical distribution. The net effect may be to lead to dominance of mat‐forming plants in low‐energy environments and non‐mat‐forming plants in high‐energy environments.
Food web structure and function in two arctic streams with contrasting disturbance regimes
Authors: PARKER STEPHANIE M. , HURYN ALEXANDER D.
Published: June 2006

1. We studied the effect of substratum movement on the communities of adjacent mountain and spring tributaries of the Ivishak River in arctic Alaska (69°1′N, 147°43′W). We expected the mountain stream to have significant bed movement during summer because of storm flows and the spring stream to have negligible bed movement because of constant discharge.

2. We predicted that the mountain stream would be inhabited only by taxa able to cope with frequent bed movement. Therefore, we anticipated that the mountain stream would have lower macroinvertebrate species richness and biomass and a food web with fewer trophic levels and lower connectance than the spring stream.

3. Substrata marked in situ indicated that 57–66% of the bed moved during summer in the mountain stream and 4–20% moved in the spring stream.

4. Macroinvertebrate taxon richness was greater in the spring (25 taxa) than in the mountain stream (20 taxa). Mean macroinvertebrate biomass was also greater in the spring (4617 mg dry mass m−2) than in the mountain stream (635 mg dry mass m−2). Predators contributed 25% to this biomass in the spring stream, but only 7% in the mountain stream.

5. Bryophyte biomass was >1000 times greater in the spring stream (88.4 g ash‐free dry mass m−2) than the mountain stream (0.08 g ash‐free dry mass m−2). We attributed this to differences in substratum stability between streams. The difference in extent of bryophyte cover between streams probably explains the high macroinvertebrate biomass in the spring stream.

6. Mean food‐web connectance was similar between streams, ranging from 0.18 in the spring stream to 0.20 in the mountain stream. Mean food chain length was 3.04 in the spring stream and 1.83 in the mountain stream. Dolly Varden char (Salvelinus malma) was the top predator in the mountain stream and the American dipper (Cinclus mexicanus) was the top predator in the spring stream. The difference in mean food chain length between streams was due largely to the presence of C. mexicanus at the spring stream.

7. Structural differences between the food webs of the spring and mountain streams were relatively minor. The difference in the proportion of macroinvertebrate biomass contributing to different trophic levels was major, however, indicating significant differences in the volume of material and energy flow between food‐web nodes (i.e. food web function).
A ‘polarisation sun‐dial’ dictates the optimal time of day for dispersal by flying aquatic insects
Authors: CSABAI ZOLTÁN , BODA PÁL , BERNÁTH BALÁZS , KRISKA GYÖRGY , HORVÁTH GÁBOR
Published: June 2006

1. Daily changes in the flight activity of aquatic insects have been investigated in only a few water beetles and bugs. The diel flight periodicity of aquatic insects and the environmental factors governing it are poorly understood.

2. We found that primary aquatic insects belonging to 99 taxa (78 Coleoptera, 21 Heteroptera) fly predominantly in mid‐morning, and/or around noon and/or at nightfall. There appears to be at least four different types of diurnal flight activity rhythm in aquatic insects, characterised by peak(s): (i) in mid‐morning; (ii) in the evening; (iii) both in mid‐morning and the evening; (iv) around noon and again in the evening. These activity maxima are quite general and cannot be explained exclusively by daily fluctuations of air temperature, humidity, wind speed and risks of predation, which are all somewhat stochastic.

3. We found experimental evidence that the proportion (%) P(θ) of reflecting surfaces detectable polarotactically as ‘water’ is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation (θ) for dark reflectors while P(θ) is maximal at dawn and dusk (low solar elevations) for bright reflectors under clear or partly cloudy skies.

4. From the temporal coincidence between peaks in the diel flight activity of primary aquatic insects and the polarotactic detectability P(θ) of water surfaces we conclude that the optimal times of day for aquatic insects to disperse are the periods of low and high solar elevations θ. The θ‐dependent reflection–polarisation patterns, combined with an appropriate air temperature, clearly explain why polarotactic aquatic insects disperse to new habitats in mid‐morning, and/or around noon and/or at dusk. We call this phenomenon the ‘polarisation sun‐dial’ of dispersing aquatic insects.
The effect of suspended sediments on Lake Texoma Daphnia: field distributions and in situ incubations
Authors: SCHULZE PETER C. , GILLESPIE J. HAYLEY , WOMBLE J. RUSSELL , SILEN ALEXANDRA F.
Published: June 2006

1. We measured the abundance and eggs per female of four Daphnia species in turbid and relatively clear regions of Lake Texoma (Oklahoma‐Texas, U.S.A.) on 12 dates over the course of 5 years.

2. Two species, Daphnia lumholtzi and Daphnia parvula, occurred and reproduced in turbid locations, but two other species, Daphnia mendotae and Daphnia pulicaria, occurred almost exclusively in relatively clear conditions.

3. To test the hypothesis that interference with foraging excludes clear‐water Daphnia species from turbid locations, we incubated adult D. mendotae at both a clear and a turbid site. In three successive experiments D. mendotae individuals incubated at the turbid site carried as many or more eggs than individuals incubated at the clear site.
Maintenance of self‐renewal ability of mouse embryonic stem cells in the absence of DNA methyltransferases Dnmt1, Dnmt3a and Dnmt3b
Authors: Tsumura Akiko , Hayakawa Tomohiro , Kumaki Yuichi , Takebayashi Shin‐ichiro , Sakaue Morito , Matsuoka Chisa , Shimotohno Kunitada , Ishikawa Fuyuki , Li En , Ueda Hiroki R. , Nakayama Jun‐ichi , Okano Masaki
Published: June 2006

DNA methyltransferases Dnmt1, Dnmt3a and Dnmt3b cooperatively regulate cytosine methylation in CpG dinucleotides in mammalian genomes, providing an epigenetic basis for gene silencing and maintenance of genome integrity. Proper CpG methylation is required for the normal growth of various somatic cell types, indicating its essential role in the basic cellular function of mammalian cells. Previous studies using Dnmt1−/– or Dnmt3a−/–Dnmt3b−/– ES cells, however, have shown that undifferentiated embryonic stem (ES) cells can tolerate hypomethylation for their proliferation. In an attempt to investigate the effects of the complete loss of CpG DNA methyltransferase function, we established mouse ES cells lacking all three of these enzymes by gene targeting. Despite the absence of CpG methylation, as demonstrated by genome‐wide methylation analysis, these triple knockout (TKO) ES cells grew robustly and maintained their undifferentiated characteristics. TKO ES cells retained pericentromeric heterochromatin domains marked with methylation at Lys9 of histone H3 and heterochromatin protein‐1, and maintained their normal chromosome numbers. Our results indicate that ES cells can maintain stem cell properties and chromosomal stability in the absence of CpG methylation and CpG DNA methyltransferases.
Long‐distance seed dispersal, clone longevity and lack of phylogeographical structure in the European distributional range of the coastal Calystegia soldanella (L.) R. Br. (Convolvulaceae)
Authors: Arafeh Rami , Kadereit Joachim W.
Published: June 2006

Aim  To explore the relative effects of Quaternary climatic history vs. species‐specific biological properties (high seed dispersability, high seed longevity, clonal growth) on phylogeographical structure in European Mediterranean and Atlantic Ocean and Black Sea material of the coastal dune plant Calystegia soldanella (L.) R. Br.

Location  Black Sea and European Mediterranean and Atlantic Ocean coasts.

Methods  Variation in amplified fragment length polymorphism was analysed at two different sampling levels. First, an entire‐range sample from the Black Sea to the North Sea, including single individuals from sites evenly spread along this entire coast was analysed. Second, in a population‐level sample, seven populations from the European Mediterranean and Atlantic Ocean coasts were analysed.

Results  Neither the entire‐range nor the population‐level sampling resulted in clear phylogeographical patterns. Instead, individuals from geographically distant areas were often genetically more similar to each other than individuals from the same area. Non‐significant isolation‐by‐distance was found for both sampling approaches, and comparatively low levels of intrapopulational genetic variation were observed.

Main conclusions  The lack of phylogeographical structure in C. soldanella, in comparison with the clear phylogeographical patterns observed in other coastal plant species analysed previously, is postulated to be the result of the specific biology of C. soldanella. The combination of high seed longevity, high dispersability of seeds by sea water and clonal growth and probable high clone age are likely to be responsible for the observed absence of phylogeographical structure. This implies that extreme biological properties such as those shown by C. soldanella can either erase or prevent the formation of historical patterns of genetic variation.
Species groups can be transferred across different scales
Authors: Petřík Petr , Bruelheide Helge
Published: June 2006

Aim To test whether species groups (i.e. assemblages of species co‐occurring in nature) that are statistically derived at one scale (broad, medium, or fine scale) can be transferred to another scale, and to identify the driving forces that determine species groups at the various scales.

Location Northern Bohemia (Czech Republic, central Europe) in the Ještědský hřbet mountain range and its neighbourhood.

Methods Three data sets were sampled: a floristic data set at the broad scale, another floristic data set at the intermediate scale, and a vegetation data set at the habitat scale. First, in each data set, species groups were produced by the COCKTAIL algorithm, which ensures maximized joint occurrence in the data set using a fidelity coefficient. Corresponding species groups were produced in the individual data sets by employing the same species for starting the algorithm. Second, the species groups formed in one data set, i.e. at a particular scale, were applied crosswise to the other data sets, i.e. to the other scales. Correspondence of a species group formed at a particular scale with a species group at another scale was determined. Third, to highlight the driving factors for the distribution of the plant species groups at each scale, canonical correspondence analysis was carried out.

Results Twelve species groups were used to analyse the transferability of the groups across the three scales, but only six of them were found to be common to all scales. Correspondence of species groups derived from the finest scale with those derived at the broadest scale was, on average, higher than in the opposite direction. Forest (tree layer) cover, altitude and bedrock type explained most of the variability in canonical correspondence analysis across all scales.

Main conclusions Transferability of species groups distinguished at a fine scale to broader scales is better than it is in the opposite direction. Therefore, a possible application of the results is to use species groups to predict the potential occurrence of missing species in broad‐scale floristic surveys from fine‐scale vegetation‐plot data.
Colonization of Sphagnum on land uplift islands in the Baltic Sea: time, area, distance and life history
Authors: Sundberg S. , Hansson J. , Rydin H.
Published: June 2006

Aim  To test whether species richness of Sphagnum mosses on islands in a land uplift archipelago is related to island age, area or connectivity, and whether the frequency of different species can be predicted by their life history and autecology.

Location  The northern Stockholm archipelago in the Baltic Sea, east‐central Sweden, with a current land uplift rate of 4.4 mm year−1.

Methods  We sampled 17 islands differing in area (0.55–55 ha), height (3.6–18 m, representing c. 800–4000 years of age) and distance from mainland (1.6–41 km). For each Sphagnum patch we measured area, height above sea level, horizontal distance from the shore and shading from vascular plants. Factors affecting island species richness, species frequency and habitats on the islands were tested by stepwise regressions. Species frequency was tested on nine life history and autecological variables, including estimated abundance and spore output on the mainland, habitat preference and distribution.

Results  We recorded 500 patches of 19 Sphagnum species, distributed in 83 rock pools on 14 islands. Island species richness correlated positively with island area and with degree of shelter by surrounding islands, while distance from the mainland, connectivity, height or age did not add to the model. Species frequency (number of colonized islands and rock pools) was mainly predicted by spore output on the mainland and by habitat preference (swamp forest species were more frequent than others), while spore size, for example, did not add to the model. Species differed in mean height above and horizontal distance from the shore, area of occupied rock pools and in the degree of shading of patches. The mean horizontal distance from the shore and the area of occupied rock pools correlated positively with the normal growth position above the water table among species. Spore capsules were found in only 2% of patches, mostly in the bisexual Sphagnum fimbriatum.

Main conclusions  The presence of Sphagnum in the Stockholm archipelago seems to be governed by regional spore production and habitat demands. Sphagnum does not appear to be dispersal limited at distances up to 40 km and time spans of centuries. Species with a high regional spore output have had a higher colonization rate, which, together with the rarity of spore capsules on the islands, indicate the mainland as a source for colonization rather than dispersal among islands. Swamp forest species seem more tolerant to the island conditions (summer droughts and some salt spray) than open mire species. The different distances from the sea occupied by the species indicate a slow, continuous succession and species replacement towards the island interior as islands are being uplifted and thus expand in area. This partly explains why larger islands harbour more species. Our results thus support some of the island biogeographical theories related to the species–area relationship.
The mode of action of the lantibiotic lacticin 3147 – a complex mechanism involving specific interaction of two peptides and the cell wall precursor lipid II
Authors: Wiedemann Imke , Böttiger Tim , Bonelli Raquel R. , Wiese Andre , Hagge Sven O. , Gutsmann Thomas , Seydel Ulrich , Deegan Lucy , Hill Colin , Ross Paul , Sahl Hans‐Georg
Published: June 2006

Lacticin 3147 is a two‐peptide lantibiotic produced by Lactococcus lactis in which both peptides, LtnA1 and LtnA2, interact synergistically to produce antibiotic activities in the nanomolar concentration range; the individual peptides possess marginal (LtnA1) or no activity (LtnA2). We analysed the molecular basis for the synergism and found the cell wall precursor lipid II to play a crucial role as a target molecule. Tryptophan fluorescence measurements identified LtnA1, which is structurally similar to the lantibiotic mersacidin, as the lipid II binding component. However, LtnA1 on its own was not able to substantially inhibit cell wall biosynthesis in vitro; for full inhibition, LtnA2 was necessary. Both peptides together caused rapid K+ leakage from intact cells; in model membranes supplemented with lipid II, the formation of defined pores with a diameter of 0.6 nm was observed. We propose a mode of action model in which LtnA1 first interacts specifically with lipid II in the outer leaflet of the bacterial cytoplasmic membrane. The resulting lipid II:LtnA1 complex is then able to recruit LtnA2 which leads to a high‐affinity, three‐component complex and subsequently inhibition of cell wall biosynthesis combined with pore formation.
Secretion signal of the filamentous haemagglutinin, a model two‐partner secretion substrate
Authors: Hodak Hélène , Clantin Bernard , Willery Eve , Villeret Vincent , Locht Camille , Jacob‐Dubuisson Françoise
Published: June 2006

The sorting of proteins to their proper subcellular compartment requires specific addressing signals that mediate interactions with ad hoc transport machineries. In Gram‐negative bacteria, the widespread two‐partner secretion (TPS) pathway is dedicated to the secretion of large, mostly virulence‐related proteins. The secreted TpsA proteins carry a characteristic 250‐residue‐long N‐terminal ‘TPS domain’ essential for secretion, while their TpsB transporters are pore‐forming proteins that specifically recognize their respective TpsA partners and mediate their translocation across the outer membrane. However, the nature of the secretion signal has not been elucidated yet. The whooping cough agent Bordetella pertussis secretes its major adhesin filamentous haemagglutinin (FHA) via the TpsB transporter FhaC. In this work, we show specific interactions between an N‐terminal fragment of FHA containing the TPS domain and FhaC by using two different techniques, an overlay assay and a pull‐down of the complex. FhaC recognizes only non‐native conformations of the TPS domain, corroborating the model that in vivo, periplasmic FHA is not yet folded. By generating single amino acid substitutions, we have identified interaction determinants forming the secretion signal. They are found unexpectedly far into the TPS domain and include both conserved and variable residues, which most likely explains the specificity of the TpsA–TpsB interaction. The N‐terminal domain of FhaC is involved in the FHA–FhaC interaction, in agreement with its proposed function and periplasmic localization.
Differential modulation of E. coli mRNA abundance by inhibitory proteins that alter the composition of the degradosome
Authors: Gao Junjun , Lee Kangseok , Zhao Meng , Qiu Ji , Zhan Xiaoming , Saxena Ankur , Moore Christopher J. , Cohen Stanley N. , Georgiou George
Published: June 2006

In Escherichia coli the initial step in the processing or decay of many messenger and structural RNAs is mediated by the endonuclease RNase E, which forms the core of a large RNA‐catalysis machine termed the degradosome. Previous experiments have identified a protein that globally modulates RNA abundance by binding to RNase E and regulating its endonucleolytic activity. Here we report the discovery of RraB, which interacts with a different site on RNase E and interferes with cleavage of a different set of transcripts. We show that expression of RraA or RraB in vivo is accompanied by dramatic, distinct, and inhibitor‐specific changes in degradosome composition – and that these are in turn associated with alterations in RNA decay and global transcript abundance profiles that are dissimilar to the profile observed during simple RNase E deficiency. Our results reveal the existence of endonuclease binding proteins that modulate the remodelling of degradosome composition in bacteria and argue that such degradosome remodelling is a mechanism for the differential regulation of RNA cleavages in E. coli.
Cytokine Responses to CpG DNA in Human Leukocytes
Authors: Ågren J. , Thiemermann C. , Foster S. J. , Wang J. E. , Aasen A. O.
Published: June 2006

Previous studies have implicated a role of bacterial DNA, containing unmethylated cytosine‐phosphate‐guanosine (CpG) motifs, in the initiation of systemic inflammation. This is based on the ability of CpG‐DNA to act in synergy with lipopolysaccharide (LPS) to trigger tumor necrosis factor alpha (TNFα) production in murine monocytes and to enhance LPS toxicity in rodents. In this study we investigated the capacity of CpG‐DNA to trigger and modulate cytokine responses in human leukocytes.

A human blood assay, as well as isolated cultures of monocytes and neutrophils, was exposed to the synthetic oligodeoxynucleotides (ODNs) CpG ODN (2006) and GpC ODN (2006‐GC), alone or in combination with peptidoglycan or LPS. Plasma or supernatants were isolated and analyzed for TNFα, interleukin‐1 beta (IL‐1β), IL‐6 and IL‐8 by ELISA.

In the blood, 2006 (but not 2006‐GC) induced the release of TNFα (P < 0.05) and possibly IL‐1β and IL‐6. IL‐8 was induced in a CpG‐independent manner. When co‐administered with peptidoglycan, both ODNs enhanced the release of cytokines, but not consistently CpG dependent. When co‐administered with LPS, only IL‐8 values were enhanced, whereas IL‐6 was suppressed at early time points. In monocyte and neutrophil cultures, CpG dependent induction of cytokine release was not observed. However, both ODNs inhibited LPS‐induced IL‐6.

In conclusion, the capacity of CpG DNA to trigger the release of TNFα and to enhance LPS‐induced release of this cytokine is confirmed in human whole blood, but not in adherent human monocytes. Most effects of the ODNs on cytokine release in human leukocytes were CpG independent.
Allelic Diversity and Affinity Variants of MICA are Imbalanced in Spanish Patients with Behçet's Disease
Authors: Muñoz‐Saá I. , Cambra A. , Pallarés L. , Espinosa G. , Juan A. , Pujalte F. , Matamoros N. , Milà J. , Julià M. R.
Published: June 2006

The aetiology of Behçet's disease (BD) is still unknown, but genetic and environmental factors are involved. HLA‐B*51 is considered a susceptibility marker and some MICA alleles have also been associated. Cytotoxic T lymphocytes have been suggested as responsible for BD lesions by engaging MICA through NKG2D surface molecules. In the present study, HLA‐B and MICA alleles were typed by polymerase chain reaction using sequence‐specific primers, in 165 healthy Spanish controls and 42 BD patients. In the healthy group, MICA*008 (28.48%), MICA*004 (17.58%), MICA*002 (14.24%) and MICA*009 (9.39%) were the predominant alleles and the most common haplotype was MICA*004‐B*44 (12.12%). MICA*001 (5.15%), MICA*004, MICA*011 (4.54%) and MICA*018 (5.15%) were more frequent, and MICA*010 (1.81%) and MICA*008 were less prevalent than in other Caucasoid populations. Similar results have been reported in North African individuals and this could support the hypothesis of a common ancestral origin of both populations. The frequencies of MICA*009 and MICA*019 were significantly increased in our BD patients in comparison with controls: 22.62% versus 9.39% and 10.71% versus 1.81% respectively. The increase of MICA*019 had not been described in other BD cohorts, and it corroborates the genetic heterogeneity at MICA locus in BD patients. High‐affinity MICA alleles for NKG2D were more frequent in controls than in patients. Moreover, high‐affinity alleles were not found in homozygous BD patients. These results argue against the hypothesis of an autoaggressive response in BD patients through MICA–NKG2D interactions.
A major sulphur isotope event at c. 510 Ma: a possible anoxia–extinction–volcanism connection during the Early–Middle Cambrian transition?
Authors: Hough M.L. , Shields G.A. , Evins L.Z. , Strauss H. , Henderson R.A. , Mackenzie S.
Published: June 2006

A new approach to constraining seawater δ34S and sulphate concentration using francolite‐bound sulphate reveals an abrupt increase in δ34S to +50‰ around the Early–Middle Cambrian boundary. Such high δ34S values are best explained by increased rates of pyrite burial due to ocean anoxia coupled with an increased sensitivity of the ocean sulphate reservoir to perturbations due to low sulphate concentrations of 500–700 μgL−1. We argue that the spread of anoxic waters at this time was partly the result of greenhouse warming related to the eruption of the Kalkarindji Large Igneous Province of northern Australia and that it triggered the collapse of early metazoan reef ecosystems during the latest Early Cambrian. Mass extinctions of the last 260 Myr have all coincided with enhanced volcanic activity, while several are also associated with positive shifts in seawater δ34S. Extending this correlation back in time further implicates volcanically induced climate change as a major determining factor in biosphere evolution.

Terra Nova, 18, 257–263, 2006
Damage analysis for structural integrity and durability of composite materials
Authors: TALREJA R.
Published: June 2006

Composite structures for mechanical and aerospace applications are designed to retain structural integrity and remain durable for the intended service life. Since the early 1970s important advances have been made in characterizing and modelling the underlying mechanical behaviour and developing tools and methodologies for predicting fracture and fatigue of composite materials. This paper presents a review of the concepts and analyses related to this area, and illustrates these by a few examples. The topics discussed are composite material strength in tension, compression and shear, damage and its progression in monotonic and cyclic loading, fatigue life prediction and damage induced changes in visco‐elastic response.
Fatigue behaviour of SiCp‐reinforced aluminium composites in the very high cycle regime using ultrasonic fatigue
Authors: HUANG J. , SPOWART J. E. , JONES J. W.
Published: June 2006

The fatigue behaviour of a 2009/SiC/15p‐T4 DRA composite has been examined in the very high cycle fatigue (VHCF) regime where 107≤Nf≤ 109 cycles. Ultrasonic fatigue was used to achieve the very high cycle counts. Careful processing yielded a composite with a very homogeneous particle distribution with minimal clustering. Fatigue crack initiation was observed almost exclusively at AlCuFe inclusions with no crack initiation observed at SiC particle clusters. Fatigue lives at a given stress level exhibited minimal scatter and subsurface crack initiation was observed in all cases. This behaviour is consistent with the presence of a low number density of critical inclusions that are responsible for crack initiation very early in fatigue life.
Limited weld residual stress measurements in fatigue crack propagation: Part I. Complete field representation through least‐squares finite‐element smoothing
Authors: GE Y. Z. , SUTTON M. A. , DENG X. , REYNOLDS A. P.
Published: June 2006

An equilibrium‐based, weighted least‐squares algorithm is developed to reconstruct the complete residual stress field tensor throughout the specimen volume using a limited set of residual stress measurements and a priori boundary conditions.

Using a set of residual stress data acquired by neutron diffraction over a limited region of an AA2024‐T351 friction‐stir‐welded specimen, the method is used to reconstruct the complete residual stress tensor field. Results indicate that (1) the algorithm is robust and effective in quantifying the complete residual stress field throughout the region of interest; (2) appropriate smoothing parameters are readily obtained so that the reconstructed, complete residual stress field accurately reflects the experimental measurements and (3) the resulting residual stress field is in self‐equilibrium.
Limited weld residual stress measurements in fatigue crack propagation: Part II. FEM‐based fatigue crack propagation with complete residual stress fields
Authors: SUTTON M. A. , REYNOLDS A. P. , GE Y. Z. , DENG X.
Published: June 2006

Using a limited set of residual stress measurements acquired by neutron diffraction and an equilibrium‐based, weighted least square algorithm to reconstruct the complete residual stress tensor field from the measured residual stress data, the effect of weld residual stress on fatigue crack propagation is investigated for 2024‐T351 aluminium alloy plate joined by friction stir welding. Through incorporation of the least squares, complete equilibrated residual stress field into a finite element model of the Friction Stir Weld (FSW) region, progressive crack growth along a direction perpendicular to the welding line is simulated as part of the analysis. Both the residual stress redistribution and the stress intensity factor due to the residual stress field, Kres, are calculated during the crack extension process.

Results show that (a) incorporation of the complete, self‐equilibrated residual stress field into a finite element (FE) model of the specimen provides a robust, hybrid approach for assessing the importance of residual stress on fatigue crack propagation, (b) the calculated stress‐intensity factor due to the residual stress field, Kres, has the same trend as measured experimentally by the ‘cut‐compliance method’ and (c) the da/dN results are readily explained with reference to the effect of the residual stress field on the applied stress intensity factor.
Thermographic analysis in ultrasonic fatigue tests
Authors: XUE H. , WAGNER D. , RANC N. , BAYRAKTAR E.
Published: June 2006

Three kinds of alloys used in the automotive industry for structures and engine components are subjected to very high cycle fatigue damage during working service. In the study, fatigue damage progression of the three kinds of alloys was investigated in the very high cycles fatigue regime by means of thermographic analysis. The specimens have been tested at ambient temperature without cooling air using a piezoelectric fatigue system (20 kHz) with a stress ratio of R=−1 to determine the effects of increased specimen temperature caused by internal damping due to cycling at a very high frequency. The temperature evolution of specimens for different alloys at various load levels have been recorded. Results indicated that the temperature evolution of the fatigue specimen depends on the material, testing frequency and loading level; the temperature increased just at the beginning of the test, which corresponds to the thermal dissipation in the specimen. In the process of small crack propagation, the temperature in a local plastic zone increased sharply, evidently irreversible local plastic deformation can result in a local temperature increase. The basis of microstructural characterization and fracture surface analysis by scanning electron microscopy, it was found that the temperature field in an ultrasonic fatigue specimen corresponds to the fatigue damage process.
A novel test method to measure the fracture toughness of ceramic balls used in bearings
Authors: PIOTROWSKI A. E. , O'Brien M. J.
Published: June 2006

A novel mechanical test has been developed to measure the fracture toughness of the silicon‐nitride (Si3N4) balls used in modern hybrid bearings. The ball is compressed diametrally between two hemispherical conforming dies, which causes the ball's equator to bulge, generating a tensile hoop stress. Under applied load, a precrack placed at the equator grows. To calculate the ball's fracture toughness at crack instability, finite‐element calculations of the applied stress field and an analytical solution for the stress intensity factor are used in the ‘two point plus semiellipse’ method. Tests of 16 Si3N4 balls and three soda‐lime glass balls gave fracture toughness measurements in good agreement with accepted published values. The new technique appears to be more accurate than the indentation technique used to measure the toughness of ceramics. As future work, the test can be extended to measure fatigue and stress corrosion properties for Si3N4 balls.
Rebutting the suggestion that Anthony Giddens’s Structuration Theory offers a useful framework for sociological nursing research: a critique based upon Margaret Archer’s Realist Social Theory
Authors: Lipscomb Martin
Published: June 2006

Abstract  A recent paper in this journal by Hardcastle et al. in 2005 argued that Anthony Giddens’s Structuration Theory (ST) might usefully inform sociological nursing research. In response, a critique of ST based upon the Realist Social Theory of Margaret Archer is presented. Archer maintains that ST is fatally flawed and, in consequence, it has little to offer nursing research. Following an analysis of the concepts epiphenomenalism and elisionism, it is suggested that emergentist Realist Social Theory captures or describes a more coherent explanatory vision of social reality than other perspectives and nurse researchers are advised to consider its potential.
Perceiving the moral dimension of practice: insights from Murdoch, Vetlesen, and Aristotle
Authors: Scott P. Anne
Published: June 2006

Abstract  This paper situates the moral domain of practice within the context of a particular description of nursing practice – one that sees human interaction at the heart of that practice. Such a description fits not only with professional rhetoric but also with literature from patients and recent empirical work exploring the nature of nursing practice.

Martha Levine in her 1977 description of ethics, within the context of nursing practice, indicated that what was important from an ethical perspective was how we interact with each other, with patients and colleagues, on a daily basis. What enables such interaction to display moral sensitivity, insight into patient need, and a focus on the good for the patient? Of relevance when answering this question is the empirical evidence indicating that professional socialization, as a nurse or a doctor, may dull the individual’s moral sense. If this is the case, cognizance needs to be taken of such evidence when identifying theoretical approaches from mainstream ethics that may provide insight and value for nurse education. It is suggested that such insight and value can be gained from a consideration of the work of Aristotle, Murdoch, and Vetlesen.
Bearing witness: a moral way of engaging in the nurse–person relationship
Authors: Naef Rahel
Published: June 2006

Abstract  For nursing, the idea of bearing witness is of utmost importance. Nurses are present with persons who experience changes in their health and quality of life and who live intense and profound moments of struggling, questioning, and finding meaning. Nurses are also with persons from moment to moment as their lives unfold, and when joy, serenity, contentment, vulnerability, sadness, fear, and suffering are experienced. In this paper, it is proposed that bearing witness is a moral way of engaging in the nurse–person relationship. Based on Levinas’s ethics of the face, it is claimed that bearing witness is enacting one’s moral responsibility, which arises from the encounter with the other. Drawing on Parse’s human becoming theory, ways of witnessing and bearing witness are defined and discussed. It is suggested that bearing witness is a human‐to‐human way of being‐relating, a mode of human coexistence. Bearing witness is being present and attentive to the truth of another’s experiences. Moreover, in this paper, the ways nurses enact their moral agency and bear witness to others placed in their care, or turn away, are explored. Nurses’ moral agency is located in the constrained moral space of contemporary health care. Hence, the creation of a moral space, which allows nurses to enact their moral responsibility of bearing witness to other persons’ experiences of health and quality of life, is called for. In doing so, it is suggested that the act of bearing witness needs a specific nursing knowledge base and a recognition that being present and being with another is a valuable nursing practice that is utterly meaningful for persons who are living through difficult times.
A pluralist view of nursing ethics
Authors: McCarthy Joan
Published: June 2006

Abstract  This paper makes the case for a pluralist, contextualist view of nursing ethics. In defending this view, I briefly outline two current perspectives of nursing ethics – the Traditional View and the Theory View. I argue that the Traditional View, which casts nursing ethics as a subcategory of healthcare ethics, is problematic because it (1) fails to sufficiently acknowledge the unique nature of nursing practice; and (2) applies standard ethical frameworks such as principlism to moral problems which tend to alienate or undermine nursing ethical concerns. Alternatively, the Theory View, which aims to build an independent and comprehensive theory of nursing ethics, is also found wanting because it (1) fails to sufficiently acknowledge the heterogeneous nature of nursing practices; (2) overemphasizes the differences and undervalues the similarities between nurses and other health professionals; and (3) assumes that one ethical framework can be meaningfully applied across diverse moral problems and contexts.

My alternative, is to argue that nursing ethics inquiry should take a pluralist and critical stance towards available ethical frameworks and the negotiation of the ethical realm. On this view, the search for moral consensus or a unique ethical framework for nursing is replaced by the task of working strategically with multiple frameworks in order to expand the moral agency of nurses and empower them to positively engage with moral uncertainty as an inevitable feature of living a moral life. I conclude by indicating some of the implications that this has for the teaching of nursing ethics.
Nursing Philosophy
Authors: Paley John
Published: June 2006

Special issue

Philosophy and palliative care

Guest editor: John Paley
EFNS guideline on diagnosis and management of post‐polio syndrome. Report of an EFNS task force
Authors: Farbu E. , Gilhus N. E. , Barnes M. P. , Borg K. , De Visser M. , Driessen A. , Howard R. , Nollet F. , Opara J. , Stalberg E.
Published: June 2006

Post‐polio syndrome (PPS) is characterized by new or increased muscular weakness, atrophy, muscle pain and fatigue several years after acute polio. The aim of the article is to prepare diagnostic criteria for PPS, and to evaluate the existing evidence for therapeutic interventions. The Medline, EMBASE and ISI databases were searched. Consensus in the group was reached after discussion by e‐mail. We recommend Halstead's definition of PPS from 1991 as diagnostic criteria. Supervised, aerobic muscular training, both isokinetic and isometric, is a safe and effective way to prevent further decline for patients with moderate weakness (Level B). Muscular training can also improve muscular fatigue, muscle weakness and pain. Training in a warm climate and non‐swimming water exercises are particularly useful (Level B). Respiratory muscle training can improve pulmonary function. Recognition of respiratory impairment and early introduction of non‐invasive ventilatory aids prevent or delay further respiratory decline and the need for invasive respiratory aid (Level C). Group training, regular follow‐up and patient education are useful for the patients’ mental status and well‐being. Weight loss, adjustment and introduction of properly fitted assistive devices should be considered (good practice points). A small number of controlled studies of potential‐specific treatments for PPS have been completed, but no definitive therapeutic effect has been reported for the agents evaluated (pyridostigmine, corticosteroids, amantadine). Future randomized trials should particularly address the treatment of pain, which is commonly reported by PPS patients. There is also a need for studies evaluating the long‐term effects of muscular training.
Clinical heterogeneity in mild chronic inflammatory demyelinating polyneuropathy
Authors: Rajabally Y. A. , Jacob S. , Abbott R. J.
Published: June 2006

We describe the clinical presentation, progression and electrodiagnostic features of three patients with a mild form of chronic inflammatory demyelinating polyneuropathy (CIDP). The unusually mild but also variable clinical picture was a cause of diagnostic uncertainty in all, but CIDP was eventually confirmed by extensive electrophysiological studies in each case, as well as by histology in one. Cerebrospinal fluid protein was raised in only one patient. Two patients were treated by intravenous immunoglobulins and both improved. Awareness of the existence of this relatively benign form of CIDP in its various presentations is essential as it can be functionally disabling, progress to more severe symptomatology, and as patients may benefit from immunomodulatory therapy.
Bowel dysfunction in patients with cauda equina lesions
Authors: Podnar S.
Published: June 2006

Despite their serious sequels on bowel function, lesions of the cauda equina have not been previously systematically studied in larger patient populations. This was the aim of the present report. From the registrars of a diagnostic and rehabilitation centres 67 patients with clinical, electrodiagnostic and radiological findings supportive of the cauda equina lesions were recruited. The Slovene versions of the standard questionnaires for anal incontinence and constipation were used. The responses were scored, impairments categorized and previous treatments noted. Neurological examination, electromyography (EMG) of lumbo‐sacral myotomes, quantitative anal sphincter EMG and electromyographic evaluation of the sacral reflex were performed. Severe anal incontinence/constipation was reported by 18%/0%, moderate by 36%/33%, and slight by 28%/43% of our patients. Twenty‐one per cent of patients wore pads continuously and 14% occasionally. More than half of the patients (60%) reported changes in their lifestyle due to anal incontinence. No patient had completely normal findings on neurological examination. Perianal sensory loss correlated (P < 0.05) with anal incontinence and gender with constipation (women >men). Only two patients had received medical attention for bowel dysfunction. Study thus demonstrated significant bowel impairment in patients with lesions of the cauda equina, which has received insufficient medical attention.
Intravenous synthetic peptide MBP8298 delayed disease progression in an HLA Class II‐defined cohort of patients with progressive multiple sclerosis: results of a 24‐month double‐blind placebo‐controlled clinical trial and 5 years of follow‐up treatment
Authors: Warren K. G. , Catz I. , Ferenczi L. Z. , Krantz M. J.
Published: June 2006

MBP8298 is a synthetic peptide with a sequence corresponding to amino acid residues 82–98 of human myelin basic protein (DENPVVHFFKNIVTPRT). It represents the immunodominant target for both B cells and T cells in multiple sclerosis (MS) patients with HLA haplotype DR2. Its administration in accordance with the principle of high dose tolerance results in long‐term suppression of anti‐myelin basic protein (MBP) autoantibody levels in the cerebrospinal fluid (CSF) of a large fraction of progressive MS patients. MBP8298 was evaluated in a 24‐month placebo‐controlled double‐blinded Phase II clinical trial in 32 patients with progressive MS. The objective was to assess the clinical efficacy of 500 mg of MBP8298 administered intravenously every 6 months, as measured by changes in Expanded Disability Status Scale (EDSS) scores. Contingency analysis for all patients at 24 months showed no significant difference between MBP8298 and placebo‐treatments (n = 32, P = 0.29). Contingency analysis in an HLA Class II defined subgroup showed a statistically significant benefit of MBP8298 treatment compared with placebo in patients with HLA haplotypes DR2 and/or DR4 (n = 20, P = 0.01). Long‐term follow‐up treatment and assessment of patients in this responder group showed a median time to progression of 78 months for MBP8298 treated patients compared with 18 months for placebo‐treatment (Kaplan–Meier analysis, P = 0.004; relative rate of progression = 0.23). Anti‐MBP autoantibody levels in the CSF of most MBP8298 treated patients were suppressed, but antibody suppression was not predictive of clinical benefit. Anti‐MBP autoantibodies that reappeared in the CSF of one patient at 36 months, whilst under treatment with MBP8298, were not reactive with the MBP8298 peptide in vitro. The identification of a responder subgroup (62.5% of the patients in this study) enables a more efficient design of a large confirmatory clinical trial of MBP8298. The probability that patients with other less common HLA‐DR haplotypes will respond to this treatment should not be ignored.
Clinical Features, Classification and Prognosis of Migraine and Tension-Type Headache in Children and Adolescents: A Long-Term Follow-Up Study
Authors: Kienbacher C , Wöber C , Zesch HE , Hafferl-Gattermayer A , Posch M , Karwautz A , Zormann A , Berger G , Zebenholzer K , Konrad A , Wöber-Bingöl Ç
Published: June 2006

We performed a long-term follow-up examination in children and adolescents with migraine and tension-type headache (TTH) in order to investigate the evolution of clinical features and headache diagnoses, to compare International Classification of Headache Disorders (ICHD)-I and ICHD-II criteria and to identify prognostic factors. We re-examined 227 patients (52.4± female, age 17.6 ± 3.1 years) 6.6 ± 1.6 years after their first presentation to a headache centre using identical semistructured questionnaires. Of 140 patients initially diagnosed with migraine, 25.7± were headache free, 48.6± still had migraine and 25.7± had TTH at follow-up. Of 87 patients with TTH, 37.9± were headache free, 41.4± still had TTH and 20.7± had migraine. The number of subjects with definite migraine was higher in ICHD-II than in ICHD-I at baseline and at follow-up. The likelihood of a decrease in headache frequency decreased with a changing headache location at baseline ( P < 0.0001), with the time between baseline and follow-up ( P = 0.0019), and with an initial diagnosis of migraine ( P = 0.014). Female gender and a longer time between headache onset and first examination tended to have an unfavourable impact. In conclusion, 30± of the children and adolescents presenting to a headache centre because of migraine or TTH become headache-free in the long-term. Another 20–25± shift from migraine to TTH or vice versa. ICHD-II criteria are superior to those of ICHD-I in identifying definite migraine in children and adolescents presenting to a headache centre. The prognosis is adversely affected by an initial diagnosis of migraine and by changing headache location, and it tends to be affected by an increasing time between headache onset and first presentation.